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Versions: 00 01 02 03 04 05 rfc3652                        Informational
                                                        IPR declarations
 Internet Draft                                              Sam X. Sun
 Document: draft-sun-handle-system-protocol-05.txt          Sean Reilly
 Expires: December 2003                                    Larry Lannom
                                                          Jason Petrone
                                                                   CNRI
                                                              June 2003
 
               Handle System Protocol (ver 2.1) Specification
 
 Status of this Memo
 
    This document is an Internet-Draft and is in full conformance with
    all provisions of Section 10 of RFC2026.
 
    Internet-Drafts are working documents of the Internet Engineering
    Task Force (IETF), its areas, and its working groups. Note that
    other groups may also distribute working documents as Internet-
    Drafts.
 
    Internet-Drafts are draft documents valid for a maximum of six
    months and may be updated, replaced, or obsoleted by other
    documents at any time. It is inappropriate to use Internet-Drafts
    as reference material or to cite them other than as "work in
    progress."
 
    The list of current Internet-Drafts can be accessed at
         http://www.ietf.org/ietf/1id-abstracts.txt
    The list of Internet-Draft Shadow Directories can be accessed at
         http://www.ietf.org/shadow.html.
 
 Abstract
 
    The Handle System is a general-purpose global name service that
    allows secured name resolution and administration over the public
    Internet. This document describes the protocol used for client
    software to access the Handle System for both handle resolution and
    administration. The protocol specifies the procedure for a client
    software to locate the responsible handle server of any given
    handle. It also defines the messages exchanged between the client
    and server for any handle operation.
 
 Table of Contents
 
    1.   Overview...................................................2
    2.   Protocol Elements..........................................4
    2.1  Conventions................................................4
    2.1.1  Data Transmission Order...................................4
    2.1.2  Transport Layer...........................................5
    2.1.3  Character Case............................................6
 
 
 
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    2.1.4  Standard String Type: UTF8-String.........................6
    2.2  Common Elements............................................6
    2.2.1  Message Envelope..........................................7
    2.2.2  Message Header...........................................10
    2.2.3  Message Body.............................................16
    2.2.4  Message Credential.......................................16
    2.3  Message Transmission......................................19
    3.   Handle Protocol Operations................................20
    3.1  Client Bootstrapping......................................20
    3.1.1  Global Handle Registry and its Service Information.......20
    3.1.2  Locating the Handle System Service Component.............21
    3.1.3  Selecting the Responsible Server.........................21
    3.2  Query Operation...........................................22
    3.2.1  Query Request............................................22
    3.2.2  Successful Query Response................................24
    3.2.3  Unsuccessful Query Response..............................24
    3.3  Error Response from Server................................25
    3.4  Service Referral..........................................26
    3.5  Client Authentication.....................................27
    3.5.1  Challenge from Server to Client..........................28
    3.5.2  Challenge-Response from Client to Server.................28
    3.5.3  Challenge-Response Verification-Request..................31
    3.5.4  Challenge-Response Verification-Response.................32
    3.6  Handle Administration.....................................32
    3.6.1  Add Handle Value(s)......................................33
    3.6.2  Remove Handle Value(s)...................................33
    3.6.3  Modify Handle Value(s)...................................34
    3.6.4  Create Handle............................................36
    3.6.5  Delete Handle............................................37
    3.7  Naming Authority (NA) Administration......................38
    3.7.1  List Handle(s) under a Naming Authority..................38
    3.7.2  List Sub-Naming Authorities under a Naming Authority.....39
    3.8  Session and Session Management............................40
    3.8.1  Session Setup Request....................................41
    3.8.2  Session Setup Response...................................43
    3.8.3  Session Key Exchange.....................................45
    3.8.4  Session Termination......................................46
    4.   Implementation Guidelines.................................46
    4.1  Server Implementation.....................................46
    4.2  Client Implementation.....................................47
    5.   Security Considerations...................................47
    References and Bibliography.....................................47
    Author's Addresses..............................................49
 
 1. Overview
 
    The Handle System provides a general-purpose, secured global name
    service for the Internet. It was originally conceived and described
    in a paper by Robert Kahn and Robert Wilensky [18] in 1995. The
 
 
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    Handle System defines a client server protocol in which client
    software submits requests via a network to handle servers. Each
    request describes the operation to be performed on the server. The
    server will process the request and return a message indicating the
    result of the operation. This document specifies the protocol for
    client software to access a handle server for handle resolution and
    administration. It does not include the description of the protocol
    used to manage handle servers. A discussion of the management
    protocol is out of the scope of this document and will be made
    available in a separate document. The document assumes that readers
    are familiar with the basic concepts of the Handle System as
    introduced in the "Handle System Overview" [1], as well as the data
    model and service definition given in the "Handle System Namespace
    and Service Definition" [2].
 
    The Handle System consists of a set of service components as
    defined in [2]. From the client's point of view, the Handle System
    is a distributed database for handles. Different handles under the
    Handle System may be maintained by different handle servers at
    different network locations. The handle protocol specifies the
    procedure for a client to locate the responsible handle server of
    any given handle. It also defines the messages exchanged between
    the client and server for any handle operation.
 
    Some key aspects of the handle protocol include:
 
       o The handle protocol supports both handle resolution and
         administration. The protocol follows the data and service
         model defined in [2].
 
       o A client may authenticate any server response based on the
         server's digital signature.
 
       o A server may authenticate its client as handle administrator
         via the handle authentication protocol. The handle
         authentication protocol is a challenge-response protocol that
         supports both public-key and secret-key based authentication.
 
       o A session may be established between the client and server so
         that authentication information and network resources (e.g.,
         TCP connection) may be shared among multiple operations. A
         session key can be established to achieve data integrity and
         confidentiality.
 
       o The protocol can be extended to support new operations.
         Controls can be used to extend the existing operations. The
         protocol is defined to allow future backward compatibility.
 
 
 
 
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       o Distributed service architecture. Support service referral
         among different service components.
 
       o Handles and their data types are based on the ISO-10646
         (Unicode 2.0) character set. UTF-8 [3] is the mandated
         encoding under the handle protocol.
 
    The handle protocol (version 2.1) specified in this document has
    changed significantly from its earlier versions. These changes are
    necessary due to changes made in the Handle System data model and
    the service model. Servers that implement this protocol may
    continue to support earlier versions of the protocol by checking
    the protocol version specified in the Message Envelope (see section
    2.2.1).
 
 2. Protocol Elements
 
 2.1  Conventions
 
    The following conventions are followed by the handle protocol to
    ensure interoperability among different implementations.
 
 2.1.1  Data Transmission Order
 
    The order of transmission of data packets follows the network byte
    order (also called the Big-Endian [11]). That is, when a data-gram
    consists of a group of octets, the order of transmission of those
    octets follows their natural order from left to right and from top
    to bottom, as they are read in English. For example, in the
    following diagram, the octets are transmitted in the order they are
    numbered.
 
         0                   1
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
        .-------------------------------.
        |       1       |       2       |
        |-------------------------------|
        |       3       |       4       |
        |-------------------------------|
        |       5       |       6       |
        '-------------------------------'
 
    If an octet represents a numeric quantity, the left most bit is the
    most significant bit. For example, the following diagram represents
    the value 170 (decimal).
 
 
 
 
 
 
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         0 1 2 3 4 5 6 7
        .---------------.
        |1 0 1 0 1 0 1 0|
        '---------------'
 
    Similarly, whenever a multi-octet field represents a numeric
    quantity, the left most bit is the most significant bit and the
    most significant octet of the whole field is transmitted first.
 
 2.1.2  Transport Layer
 
    The handle protocol is designed so that messages may be transmitted
    either as separate data-grams over UDP or as a continuous byte
    stream via a TCP connection. The recommended port number for both
    UDP and TCP is 2641.
 
    UDP Usage
 
    Messages carried by UDP are restricted to 512 bytes (not including
    the IP or UDP header). Longer messages must be fragmented into UDP
    packets where each packet carries a proper sequence number in the
    Message Envelope (see Section 2.2.1).
 
    The optimum retransmission policy will vary depending on the
    network or server performance, but the following are recommended:
 
       o The client should try other servers or service interfaces
         before repeating a request to the same server address.
 
       o The retransmission interval should be based on prior
         statistics if possible. Overly aggressive retransmission
         should be avoided to prevent network congestion. The
         recommended retransmission interval is 2-5 seconds.
 
       o When transmitting large amounts of data, TCP-friendly
         congestion control, such as an interface to the Congestion
         Manager [12], should be implemented whenever possible to avoid
         unfair consumption of the bandwidth against TCP-based
         applications. Details of the congestion control will be
         discussed in a separate document.
 
    TCP Usage
 
    Messages under the handle protocol can be mapped directly into a
    TCP byte-stream. However, the size of each message is limited by
    the range of a 4-byte unsigned integer. Longer messages may be
    fragmented into multiple messages before the transmission and
    reassembled at the receiving end.
 
 
 
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    Several connection management policies are recommended:
 
       o The server should support multiple connections and should not
         block other activities waiting for TCP data.
 
       o By default, the server should close the connection after
         completing the request. However, if the request asks to keep
         the connection open, the server should assume that the client
         will initiate connection closing.
 
 2.1.3  Character Case
 
    Handles are character strings based on the ISO-10646 character set
    and must be encoded in UTF-8. By default, handle characters are
    treated as case-sensitive under the handle protocol. A handle
    service, however, may be implemented in such a way that ASCII
    characters are processed case-insensitively. For example, the
    Global Handle Registry (GHR) provides a handle service where ASCII
    characters are processed in a case-insensitive manner. This
    suggests that ASCII characters in any naming authority are case-
    insensitive.
 
    When handles are created under a case-insensitive handle server,
    their original case should be preserved. To avoid any confusion,
    the server should avoid creating any handle whose character string
    matches that of an existing handle, ignoring the case difference.
    For example, if the handle "X/Y" was already created, the server
    should refuse any request to create the handle "x/y" or any of its
    case variations.
 
 2.1.4  Standard String Type: UTF8-String
 
    Handles are transmitted as UTF8-Strings under the handle protocol.
    Throughout this document, UTF8-String stands for the data type that
    consists of a 4-byte unsigned integer followed by a character
    string in UTF-8 encoding. The leading integer specifies the number
    of octets of the character string.
 
 2.2  Common Elements
 
    Each message exchanged under the system protocol consists of four
    sections (see Fig. 2.2). Some of these sections (e.g., the Message
    Body) may be empty depending on the protocol operation.
 
    The Message Envelope must always be present. It has a fixed size of
    20 octets. The Message Envelope does not carry any application
    layer information and is primarily used to help deliver the
    message. Content in the Message Envelope is not protected by the
    digital signature in the Message Credential.
 
 
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    The Message Header must always be present as well. It has a fixed
    size of 24 octets and holds the common data fields of all messages
    exchanged between client and server. These include the operation
    code, the response code, and the control options for each protocol
    operation. Content in the Message Header is protected by the
    digital signature in the Message Credential.
 
    The Message Body contains data specific to each protocol operation.
    Its format varies according to the operation code and the response
    code in the Message Header. The Message Body may be empty. Content
    in the Message Body is protected by the digital signature in the
    Message Credential.
 
    The Message Credential provides a mechanism for transport security
    for any message exchanged between the client and server. A non-
    empty Message Credential may contain the digital signature from the
    originator of the message or the one-way Message Authentication
    Code (MAC) based on a pre-established session key. The Message
    Credential may be used to authenticate the message between the
    client and server. It can also be used to check data integrity
    after its transmission.
 
      .----------------------.
      |                      |  ; Message wrapper for proper message
      |   Message Envelope   |  ; delivery. Not protected by the
      |                      |  ; digital signature in the Message
      |                      |  ; Credential.
      |----------------------|
      |                      |  ; Common data fields for all handle
      |   Message Header     |  ; operations.
      |                      |
      |----------------------|
      |                      |  ; Specific data fields for each
      |   Message Body       |  ; request/response.
      |                      |
      |----------------------|
      |                      |  ; Contains digital signature or
      |  Message Credential  |  ; message authentication code (MAC)
      |                      |  ; upon Message Header and Message
      '----------------------'  ; Body.
 
         Fig 2.2: Message format under the handle protocol
 
 2.2.1  Message Envelope
 
    Each message begins with a Message Envelope under the handle
    protocol. If a message has to be truncated before its transmission,
    each truncated portion must also begin with a Message Envelope.
 
 
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    The Message Envelope allows the reassembly of the message at the
    receiving end. It has a fixed size of 20 octets and consists of
    seven fields:
 
       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      .---------------------------------------------------------------.
      | MajorVersion  | MinorVersion  |       MessageFlag             |
      |---------------------------------------------------------------|
      |               SessionId                                       |
      |---------------------------------------------------------------|
      |               RequestId                                       |
      |---------------------------------------------------------------|
      |               SequenceNumber                                  |
      |---------------------------------------------------------------|
      |               MessageLength                                   |
      '---------------------------------------------------------------'
 
    2.2.1.1 <MajorVersion> and <MinorVersion>
 
    The <MajorVersion> and <MinorVersion> are used to identify the
    version of the handle protocol. Each of them is defined as a one-
    byte unsigned integer. This specification defines the protocol
    version whose <MajorVersion> is 2 and <MinorVersion> is 1.
 
    <MajorVersion> and <MinorVersion> are designed to allow future
    backward compatibility. A difference in <MajorVersion> indicates
    major variation in the protocol format and the party with the lower
    <MajorVersion> will have to upgrade its software to ensure precise
    communication. An increment in <MinorVersion> is made when
    additional capabilities are added to the protocol without any major
    change to the message format.
 
    2.2.1.2 <MessageFlag>
 
    The <MessageFlag> consists of two octets defined as follows:
 
                                              1   1   1   1   1   1
      0   1   2   3   4   5   6   7   8   9   0   1   2   3   4   5
     .---------------------------------------------------------------.
     |CP |EC |TC |       Reserved                                    |
     '---------------------------------------------------------------'
 
    Bit 0 is the CP (ComPressed) flag that indicates whether the
    message (excluding the Message Envelope) is compressed. If the CP
    bit is set (to 1), the message is compressed. Otherwise, the
    message is not compressed. The handle protocol uses the same
    compression method as used by the FTP protocol[8].
 
 
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    Bit 1 is the EC (EnCrypted) flag that indicates whether the message
    (excluding the Message Envelope) is encrypted. The EC bit should
    only be set under an established session where a session key is in
    place. If the EC bit is set (to 1), the message is encrypted using
    the session key. Otherwise the message is not encrypted.
 
    Bit 2 is the TC (TrunCated) flag that indicates whether this is a
    truncated message. Message truncation happens most often when
    transmitting a large message over the UDP protocol. Details of
    message truncation (or fragmentation) will be discussed in section
    2.3.
 
    Bits 3 to 15 are currently reserved and must be set to zero.
 
    2.2.1.3 <SessionId>
 
    The <SessionId> is a four-byte unsigned integer that identifies a
    communication session between the client and server.
 
    Session and its <SessionId> are assigned by a server either upon an
    explicit request from a client or when multiple message exchanges
    are expected to fulfill the client's request. For example, the
    server will assign a unique <SessionId> in its response if it has
    to authenticate the client. A client may explicitly ask the server
    to set up a session as a virtually private communication channel
    like SSL [4]. Requests from clients without an established session
    must have their <SessionId> set to zero. The server must assign a
    unique non-zero <SessionId> for each new session. It is also
    responsible for terminating those sessions that are not in use
    after some period of time.
 
    Both clients and servers must maintain the same <SessionId> for
    messages exchanged under an established session. A message whose
    <SessionId> is zero indicates that no session has been established.
 
    The session and its state information may be shared among multiple
    handle operations. They may also be shared over multiple TCP
    connections as well. Once a session is established, both client and
    server must maintain their state information according to the
    <SessionId>. The state information may include the stage of the
    conversation, the other party's authentication information, and the
    session key that was established for message encryption or
    authentication. Details of these are discussed in section 3.8.
 
    2.2.1.4 <RequestId>
 
    Each request from a client is identified by a <RequestId>, a 4-byte
    unsigned integer set by the client. Each <RequestId> must be unique
 
 
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    from all other outstanding requests from the same client. The
    <RequestId> allows the client to keep track of its requests, and
    any response from the server must include the correct <RequestId>.
 
    2.2.1.5 <SequenceNumber>
 
    Messages under the handle protocol may be truncated during their
    transmission (e.g. under UDP). The <SequenceNumber> is a 4-byte
    unsigned integer used as a counter to keep track of each truncated
    portion of the original message. The message recipient can
    reassemble the original message based on the <SequenceNumber>. The
    <SequenceNumber> must start with 0 for each message. Each truncated
    message must set its TC flag in the Message Envelope. Messages that
    are not truncated must set their <SequenceNumber> to zero.
 
    2.2.1.6 <MessageLen>
 
    A 4-byte unsigned integer that specifies the total number of octets
    of any message, excluding those in the Message Envelope. The length
    of any single message exchanged under the handle protocol is
    limited by the range of a 4-byte unsigned integer. Longer data can
    be transmitted as multiple messages with a common <RequestId>.
 
 2.2.2  Message Header
 
    The Message Header contains the common data elements among any
    protocol operation. It has a fixed size of 24 octets and consists
    of eight fields.
 
       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      .---------------------------------------------------------------.
      |                     OpCode                                    |
      |---------------------------------------------------------------|
      |                     ResponseCode                              |
      |---------------------------------------------------------------|
      |                     OpFlag                                    |
      |---------------------------------------------------------------|
      |     SiteInfoSerialNumber      | RecursionCount|               |
      |---------------------------------------------------------------|
      |                     ExpirationTime                            |
      |---------------------------------------------------------------|
      |                     BodyLength                                |
      '---------------------------------------------------------------'
 
    Every message that is not truncated must have a Message Header. If
    a message has to be truncated for its transmission, the Message
    Header must appear in the first truncated portion of the message.
 
 
 
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    This is different from the Message Envelope, which appears in each
    truncated portion of the message.
 
    2.2.2.1 <OpCode>
 
    The <OpCode> stands for operation code, which is a four-byte
    unsigned integer that specifies the intended operation. The
    following table lists the <OpCode>s that MUST be supported by all
    implementations in order to conform to the base protocol
    specification. Each operation code is given a symbolic name that is
    used throughout this document for easy reference.
 
      Op_Code    Symbolic Name            Remark
     ---------   -------------            ------
 
         0       OC_RESERVED              Reserved
         1       OC_RESOLUTION            Handle query
         2       OC_GET_SITEINFO          Get HS_SITE values
 
       100       OC_CREATE_HANDLE         Create new handle
       101       OC_DELETE_HANDLE         Delete existing handle
       102       OC_ADD_VALUE             Add handle value(s)
       103       OC_REMOVE_VALUE          Remove handle value(s)
       104       OC_MODIFY_VALUE          Modify handle value(s)
       105       OC_LIST_HANDLE           List handles
       106       OC_LIST_NA               List sub-naming authorities
 
       200       OC_CHALLENGE_RESPONSE    Response to challenge
       201       OC_VERIFY_RESPONSE       Verify challenge response
 
       300
        :        { Reserved for handle server administration }
       399
 
       400       OC_SESSION_SETUP         Session setup request
       401       OC_SESSION_TERMINATE     Session termination request
       402       OC_SESSION_EXCHANGEKEY   Session key exchange
 
    A detailed description of each of these <OpCode>s can be found in
    section 3 of this document. In general, clients use the <OpCode> to
    tell the server what kind of handle operation they want to
    accomplish. Response from the server must maintain the same
    <OpCode> as the original request and use the <ResponseCode> to
    indicate the result.
 
    2.2.2.2. <ResponseCode>
 
    The <ResponseCode> is a 4-byte unsigned integer that is given by a
    server to indicate the result of any service request. The list of
 
 
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    <ResponseCode>s used in the handle protocol is defined in the
    following table. Each response code is given a symbolic name that
    is used throughout this document for easy reference.
 
 
       Res. Code   Symbolic Name            Remark
       ---------   -------------            ------
 
          0        RC_RESERVED              Reserved for request
          1        RC_SUCCESS               Success response
          2        RC_ERROR                 General error
          3        RC_SERVER_BUSY           Server too busy to respond
          4        RC_PROTOCOL_ERROR        Corrupted or
                                            unrecognizable message
          5        RC_OPERATION_DENIED      Unsupported operation
          6        RC_RECUR_LIMIT_EXCEEDED  Too many recursions for
                                            the request
 
          100      RC_HANDLE_NOT_FOUND      Handle not found
          101      RC_HANDLE_ALREADY_EXIST  Handle already exists
          102      RC_INVALID_HANDLE        Encoding (or syntax) error
 
          200      RC_VALUE_NOT_FOUND       Value not found
          201      RC_VALUE_ALREADY_EXIST   Value already exists
          202      RC_VALUE_INVALID         Invalid handle value
 
          300      RC_EXPIRED_SITE_INFO     SITE_INFO out of date
          301      RC_SERVER_NOT_RESP       Server not responsible
          302      RC_SERVICE_REFERRAL      Server referral
          303      RC_NA_DELEGATE           Naming authority delegation
                                            takes place.
 
          400      RC_NOT_AUTHORIZED        Not authorized/permitted
          401      RC_ACCESS_DENIED         No access to data
          402      RC_AUTHEN_NEEDED         Authentication required
          403      RC_AUTHEN_FAILED         Failed to authenticate
          404      RC_INVALID_CREDENTIAL    Invalid credential
          405      RC_AUTHEN_TIMEOUT        Authentication timed out
          406      RC_UNABLE_TO_AUTHEN      Unable to authenticate
 
          500      RC_SESSION_TIMEOUT       Session expired
          501      RC_SESSION_FAILED        Unable to establish session
          502      RC_NO_SESSION_KEY        No session yet available
          503      RC_SESSION_NO_SUPPORT    Session not supported
          504      RC_SESSION_KEY_INVALID   Invalid session key
 
          900      RC_TRYING                Request under processing
          901      RC_FORWARDED             Request forwarded to
                                            another server
 
 
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          902      RC_QUEUED                Request queued for later
                                            processing
 
    Response codes under 10000 are reserved for system use. Any message
    with a response code under 10000 but not listed above should be
    treated as an unknown error. Response codes above 10000 are user
    defined and can be used for application specific purposes.
 
    Detailed descriptions of these <ResponseCode>s can be found in
    section 3 of this document. In general, any request from client
    must have its <ResponseCode> set to 0. The response message from
    the server must have a non-zero <ResponseCode> to indicate the
    result. For example, a response message from a server with
    <ResponseCode> set to RC_SUCCESS indicates that the server has
    successfully fulfilled the client's request.
 
    2.2.2.3. <OpFlag>
 
    The <OpFlag> is a 32-bit bit-mask that defines various control
    options for protocol operation. The following figure shows the
    location of each option flag in the <OpFlag> field.
 
                                              1   1   1   1   1   1
      0   1   2   3   4   5   6   7   8   9   0   1   2   3   4   5
      .---------------------------------------------------------------.
      |AT |CT |ENC|REC|CA |CN |KC |PO |RD |    Reserved               |
      |---------------------------------------------------------------|
      |                              Reserved                         |
      '---------------------------------------------------------------'
 
       AT   -  AuThoritative bit. A request with the AT bit set (to 1)
               indicates that the request should be directed to the
               primary service site (instead of any mirroring sites). A
               response message with the AT bit set (to 1) indicates
               that the message is returned from a primary server
               (within the primary service site).
 
       CT   -  CerTified bit. A request with the CT bit set (to 1) asks
               the server to sign its response with its digital
               signature. A response with the CT bit set (to 1)
               indicates that the message is signed. The server must
               sign its response if the request has its CT bit set (to
               1). If the server fails to provide valid signature in
               its response, the client should discard the response and
               treat the request as failed.
 
       ENC  -  ENCryption bit. A request with the ENC bit set (to 1)
               requires the server to encrypt its response using the
               pre-established session key.
 
 
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       REC  -  RECursive bit. A request with the REC bit set (to 1)
               asks the server to forward the query on behalf of the
               client if the request has to be processed by another
               handle server. The server may honor the request by
               forwarding the request to the appropriate handle server
               and passing on any result back to the client. The server
               may also deny any such request by sending a response
               with <ResponseCode> set to RC_SERVER_NOT_RESP.
 
       CA   -  Cache Authentication. A request with the CA bit set (to
               1) asks the caching server (if any) to authenticate any
               server response (e.g., verifying the server's signature)
               on behalf of the client. A response with the CA bit set
               (to 1) indicates that the response has been
               authenticated by the caching server.
 
       CN   -  ContiNuous bit. A message with the CN bit set (to 1)
               tells the message recipient that more messages that are
               part of the same request (or response) will follow. This
               happens if a request (or response) has data that is too
               large to fit into any single message and has to be
               fragmented into multiple messages.
 
       KC   -  Keep Connection bit. A message with the KC bit set
               requires the message recipient to keep the TCP
               connection open (after the response is sent back). This
               allows the same TCP connection to be used for multiple
               handle operations.
 
       PO   -  Public Only bit. Used by query operations only. A query
               request with the PO bit set (to 1) indicates that the
               client is only asking for handle values that have the
               PUB_READ permission. A request with PO bit set to zero
               asks for all the handle values regardless of their read
               permission. If any of the handle values require
               ADMIN_READ permission, the server must authenticate the
               client as the handle administrator.
 
       RD   -  Request-Digest bit. A request with the RD bit set (to 1)
               asks the server to include in its response the message
               digest of the request. A response message with the RD
               bit set (to 1) indicates that the first field in the
               Message Body contains the message digest of the original
               request. The message digest can be used to check the
               integrity of the server response. Details of these are
               discussed later in this document.
 
 
 
 
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    All other bits in the <OpFlag> field are reserved and must be set
    to zero.
 
    In general, servers must honor the <OpFlag> specified in the
    request. If a requested option cannot be met, the server should
    return an error message with the proper <ResponseCode> as defined
    in the previous section.
 
    2.2.2.4. <SiteInfoSerialNumber>
 
    The <SiteInfoSerialNumber> is a two-byte unsigned integer. The
    <SiteInfoSerialNumber> in a request refers to the <SerialNumber> of
    the HS_SITE value used by the client (to access the server).
    Servers can check the <SiteInfoSerialNumber> in the request to find
    out if the client has up-to-date service information.
 
    When possible, the server should fulfill a client's request even if
    the service information used by the client is out-of-date. However,
    the response message should specify the latest version of service
    information in the <SiteInforSerialNumber> field. Clients with out-
    of-date service information can update the service information from
    the Global Handle Registry. If the server cannot fulfill a client's
    request due to expired service information, it should reject the
    request and return an error message with <ResponseCode> set to
    RC_EXPIRED_SITE_INFO.
 
    2.2.2.5. <RecursionCount>
 
    The <RecursionCount> is a one-byte unsigned integer that specifies
    the number of service recursions. Service recursion happens if the
    server has to forward the client's request to another server. Any
    request directly from the client must have its <RecursionCount> set
    to 0. If the server has to send a recursive request on behalf of
    the client, it must increment the <RecursionCount> by 1. Any
    response from the server must maintain the same <RecursionCount> as
    the one in the request. To prevent an infinite loop of service
    recursion, the server should be configurable to stop sending a
    recursive request when the <RecursionCount> reaches a certain
    value.
 
    2.2.2.6. <ExpirationTime>
 
    The <ExpirationTime> is a 4-byte unsigned integer that specifies
    the time when the message should be considered expired, relative to
    January 1st, 1970 GMT, in seconds. It is set to zero if no
    expiration is expected.
 
    2.2.2.7. <BodyLength>
 
 
 
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    The <BodyLength> is a 4-byte unsigned integer that specifies the
    number of octets in the Message Body. The <BodyLength> does not
    count the octets in the Message Header or those in the Message
    Credential.
 
 2.2.3  Message Body
 
    The Message Body always follows the Message Header. The number of
    octets in the Message Body can be determined from the <BodyLength>
    in the Message Header. The Message Body may be empty. The exact
    format of the Message Body depends on the <OpCode> and the
    <ResponseCode> in the Message Header. Details of the Message Body
    under each <OpCode> and <ResponseCode> are described in section 3
    of this document.
 
    For any response message, if the Message Header has its RD bit (in
    <OpFlag>) set to 1, the Message Body must begin with the message
    digest of the original request. The message digest is defined as
    follows:
 
      <RequestDigest> ::= <DigestAlgorithmIdentifier>
                          <MessageDigest>
 
        where
 
          <DigestAlgorithmIdentifier>
          An octet that identifies the algorithm used to generate the
          message digest. If the octet is set to 1, the digest is
          generated using the MD5 [9] algorithm. If the octet is set to
          2, SHA-1 [10] algorithm is used.
 
          <MessageDigest>
          The message digest itself. It is calculated upon the Message
          Header and the Message Body of the original request. The
          length of the field is fixed according to the digest
          algorithm. For MD5 algorithm, the length is 16 octets. For
          SHA-1, the length is 20 octets.
 
    The Message Body may be truncated into multiple portions during its
    transmission (e.g. over UDP). Recipient of such message may
    reassemble the Message Body from each portion based on the
    <SequenceNumber> in the Message Envelop.
 
 2.2.4  Message Credential
 
    The Message Credential is primarily used to carry any digital
    signatures signed by the message issuer. It may also carry the
    Message Authentication Code (MAC) if a session key has been
    established. The Message Credential is used to protect contents in
 
 
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    the Message Header and the Message Body from being tampered with
    during the transmission. The format of the Message Credential is
    designed to be semantically compatible with PKCS#7 [5]. Each
    Message Credential consists of the following fields:
 
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      .---------------------------------------------------------------.
      |           CredentialLength                                    |
      |---------------------------------------------------------------|
      |   Version     |    Reserved   |       Options                 |
      |---------------------------------------------------------------|
      |
      |   Signer: <Handle, Index>
      |
      |---------------------------------------------------------------|
      |           Type      (UTF8-String)                             |
      |---------------------------------------------------------------|
      |
      |   SignedInfo: <Length> : 4-byte unsigned integer
      |               DigestAlgorithm: <UTF8-String>
      |               SignedData: <Length, Signature>
      |
      '---------------------------------------------------------------'
 
    where
 
      <CredentialLength>
      A 4-byte unsigned integer that specifies the number of octets in
      the Message Credential. It must be set to zero if the message has
      no Message Credential.
 
      <Version>
      An octet that identifies the version number of the Message
      Credential. The version number specified in this document is
      zero.
 
      <Reserved>
      An octet that must be set to zero.
 
      <Options>
      Two octets reserved for various cryptography options.
 
      <Signer> ::= <HANDLE>
                   <INDEX>
      A reference to a handle value in terms of the <HANDLE> and the
      <INDEX> of the handle value. The handle value may contain the
      public key, or the X.509 certificate, that can be used to
      validate the digital signature.
 
 
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      <Type>
      A UTF8-String that indicates the type of the content in the
      <SignedInfo> field (described below). It may contain HS_DIGEST if
      <SignedInfo> contains the message digest, or HS_MAC if
      <SignedInfo> contains the Message Authentication Code (MAC). The
      <Type> field will specify the signature algorithm identifier if
      <SignedInfo> contains a digital signature. For example, with the
      <Type> field set to HS_SIGNED_PSS, the <SignedInfo> field will
      contain the digital signature generated using the RSA-PSS
      algorithm [16]. If the <Type> field is set to HS_SIGNED, the
      <SignedInfo> field will contain the digital signature generated
      from a DSA public key pair.
 
      <SignedInfo> ::=  <Length>
                        <DigestAlgorithm>
                        <SignedData>
        where
 
          <Length>
          A 4-byte unsigned integer that specifies the number of octets
          in the <SignedInfo> field.
 
          <DigestAlgorithm>
          A UTF8-String that refers to the digest algorithm used to
          generate the digital signature. For example, the value "SHA-
          1" indicates that SHA-1 algorithm is used to generate the
          message digest for the signature.
 
          <SignedData> ::=  <LENGTH>
                            <SIGNATURE>
            where
 
              <LENGTH>
              A 4-byte unsigned integer that specifies the number of
              octets in the <SIGNATURE>.
 
              <SIGNATURE>
              Contains the digital signature or the MAC over the
              Message Header and Message Body. The syntax and semantics
              of the signature depend on the <Type> field and the
              public key referenced in the <Signer> field. For example,
              if the <Type> field is "HS_SIGNED" and the public key
              referred to by the <Signer> field is a DSA [6] public
              key, the signature will be the ASN.1 octet string
              representation of the parameter R and S as described in
              [7]. If the <Signer> field refers to a handle value
              that contains a X.509 certificate, the signature should
              be encoded according to RFC3279 and RFC3280 [14, 15].
 
 
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    Message Credential may contain the message authentication code
    (MAC) generated using a pre-established session key. In this case,
    the <Signer> field must set its <HANDLE> to a zero-length UTF8-
    String and its <INDEX> to the <SessionId> specified in the Message
    Envelope. The <Signature> field must contain the MAC in its
    <SIGNATURE> field. The MAC is the result of the one-way hash over
    the concatenation of the session key, the <Message Header>, the
    <MessageBody>, and the session key again.
 
    The Message Credential in a response message may contain the
    digital signature signed by the server. The server's public key can
    be found in the service information used by the client to send the
    request to the server. In this case, the client should ignore any
    reference in the <Signer> field and use the public key in the
    service information to verify the signature.
 
    Message Credential can also be used for non-repudiation purpose.
    This happens if the Message Credential contains server's digital
    signature. The signature may be used as an evidence to demonstrate
    that the server has rendered its service in response to client's
    request.
 
    Message Credential provides a mechanism for safe transmission of
    any message between the client and server. Any message whose
    Message Header and Message Body complies with its Message
    Credential suggests that the message indeed comes from its
    originator. It also assures that the message has not been tampered
    with during its transmission.
 
 2.3  Message Transmission
 
    A large message may be truncated into multiple packets during its
    transmission. For example, to fit the size limit of a UDP packet,
    the message issuer must truncate any large message into multiple
    UDP packets before its transmission. The message recipient must
    reassemble the message from these truncated packets before further
    processing. Message truncation must be carried out over the entire
    message except the Message Envelope. A new Message Envelope has to
    be inserted in front of each truncated packet before its
    transmission. For example, a large message that consists of
 
       .--------------------------------------------------------.
       |  Message Envelope  |  Message Header, Body, Credential |
       '--------------------------------------------------------'
 
    may be truncated into:
 
          .--------------------------------------------.
 
 
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          |  Message Envelope 1 |  Truncated_Packet 1  |
          '--------------------------------------------'
          .--------------------------------------------.
          |  Message Envelope 2 |  Truncated_Packet 2  |
          '--------------------------------------------'
 
             ......
 
          .--------------------------------------------.
          |  Message Envelope N |  Truncated Packet N  |
          '--------------------------------------------'
 
    where the "Truncated_packet 1", "Truncated_packet 2", ..., and
    "Truncated_packet N" result from truncating the Message Header, the
    Message Body and the Message Credential. Each "Message Envelope i"
    (inserted before each truncation) must set its TC flag to 1 and
    maintain the proper sequence count (in the <SequenceNumber>). Each
    "Message Envelope i" must also set its <MessageLength> to reflect
    the size of the packet. The recipient of these truncated packets
    can reassemble the message by concatenating these packets based on
    their <SequenceNumber>.
 
 3. Handle Protocol Operations
 
    This section describes the details of each protocol operation in
    terms of messages exchanged between the client and server. It also
    defines the format of the Message Body according to each <OpCode>
    and <ResponseCode> in the Message Header.
 
 3.1 Client Bootstrapping
 
 3.1.1  Global Handle Registry and its Service Information
 
    The service information for the Global Handle Registry (GHR) allows
    clients to contact the GHR to find out the responsible service
    components for their handles. The service information is a set of
    HS_SITE values assigned to the root handle "0.NA/0.NA" and is also
    called the root service information. The root service information
    may be distributed along with the client software, or be downloaded
    from the Handle System website at http://www.handle.net.
 
    Changes to the root service information are identified by the
    <SerialNumber> in the HS_SITE values. A server at GHR can find out
    if the root service information used by the client is outdated by
    checking the <SerialNumber> in the client's request. The client
    should update the root service information if the <ResponseCode> of
    the response message is RC_EXPIRED_SITE_INFO. Clients may obtain
    the most up-to-date root service information from the root handle.
    The GHR must sign the root service information using the public key
 
 
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    specified in the outdated service information (identified in the
    client's request) so that the client can validate the signature.
 
 3.1.2  Locating the Handle System Service Component
 
    Each handle under the Handle System is managed by a unique handle
    service component (e.g. LHS). For any given handle, the responsible
    service component (and its service information) can be found from
    its naming authority handle. Before resolving any given handle, the
    client needs to find the responsible service component by querying
    the naming authority handle from the GHR.
 
    For example, to find the responsible LHS for the handle "1000/abc",
    client software can query the GHR for the HS_SITE (or HS_SERV)
    values assigned to the naming authority handle "0.NA/1000". The set
    of HS_SITE values provides the service information of the LHS that
    manages every handle under the naming authority "1000". If no
    HS_SITE values are found, the client can check if there is any
    HS_SERV value assigned to the naming authority handle. The HS_SERV
    value provides the service handle that maintains the service
    information for the LHS. Service handles are used to manage the
    service information shared by different naming authorities.
 
    It is possible that the naming authority handle requested by the
    client does not reside at the GHR. This happens when naming
    authority delegation takes place. Naming authority delegation
    happens when a naming authority delegates a LHS to manage all its
    child naming authorities. In this case, the delegating naming
    authority must contain the service information, a set of
    HS_NA_DELEGATE values, of the LHS that manages its child naming
    authorities.
 
    All top-level naming authority handles must be registered and
    managed by the GHR. When a server at the GHR receives a request for
    a naming authority that has been delegated to a LHS, it must return
    a message with the <ResponseCode> set to RC_NA_DELEGATE, along with
    the HS_NA_DELAGATE values from the nearest ancestor naming
    authority. The client can query the LHS described by the
    HS_NA_DELAGATE values for the delegated naming authority handle. In
    practice, the ancestor naming authority should make itself
    available to any handle server within the GHR, by replicating
    itself at the time of delegation. This will prevent any cross-
    queries among handle servers (within a service site) when the
    naming authority in query and the ancestor naming authority doesn't
    hash into the same handle server.
 
 3.1.3  Selecting the Responsible Server
 
 
 
 
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    Each handle service component is defined in terms of a set of
    HS_SITE values. Each of these HS_SITE values defines a service site
    within the service component. A service site may consist of a group
    of handle servers. For any given handle, the responsible handle
    server within the service component can be found following this
    procedure:
 
        1.  Select a preferred service site.
 
            Each service site is defined in terms of an HS_SITE value.
             The HS_SITE value may contain a <Description> or other
             attributes (under the <AttributeList>) to help the
             selection. Clients must select the primary service site
             for any administrative operations.
 
        2.  Locate the responsible server within the service site.
 
             This can be done as follows: Convert every ASCII character
             in the handle to its upper case. Calculate the MD5 hash of
             the converted handle string according to the <HashOption>
             given in the HS_SITE value. Take the last 4 bytes of the
             hash result as a signed integer. Modulo the absolute value
             of the integer by the <NumOfServer> given in the HS_SITE
             value. The result is the sequence number of the
             <ServerRecord> listed in the HS_SITE value. For example,
             if the result of the modulation is 2, the third
             <ServerRecord> listed in the <HS_SITE> should be selected.
             The <ServerRecord> defines the responsible handle server
             for the given handle.
 
 3.2 Query Operation
 
    A query operation consists of a client sending a query request to
    the responsible handle server and the server returning the query
    result to the client. Query requests are used to retrieve handle
    values assigned to any given handle.
 
 3.2.1  Query Request
 
    The Message Header of any query request must set its <OpCode> to
    OC_RESOLUTION (defined in section 2.2.2.1) and <ResponseCode> to 0.
 
    The Message Body for any query request is defined as follows:
 
      <Message Body of Query Request>  ::=  <Handle>
                                            <IndexList>
                                            <TypeList>
 
        where
 
 
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          <Handle>
          A UTF8-String (as defined in section 2.1.4) that specifies
          the handle to be resolved.
 
          <IndexList>
          A 4-byte unsigned integer followed by an array of 4-byte
          unsigned integers. The first integer indicates the number of
          integers in the integer array. Each number in the integer
          array is a handle value index and refers to a handle value to
          be retrieved. The client sets the first integer to zero
          (followed by an empty array) to ask for all the handle values
          regardless of their index.
 
          <TypeList>
          A 4-byte unsigned integer followed by a list of UTF8-Strings.
          The first integer indicates the number of UTF8-Strings in the
          list that follows. Each UTF8-String in the list specifies a
          data type. This tells the server to return all handle values
          whose data type is listed in the list. If an UTF8-String ends
          with the '.' (0x2E) character, the server must return all
          handle values whose data type is under the type hierarchy
          specified in the UTF8-String. The <TypeList> may contain no
          UTF8-String if the first integer is 0. In this case, the
          server must return all handle values regardless of their data
          type.
 
    If a query request does not specify any index or data type and the
    PO flag (in the Message Header) is set, the server will return all
    the handle values that have the PUBLIC_READ permission. Clients can
    also send queries without the PO flag set. In this case, the server
    will return all the handle values with PUBLIC_READ permission and
    all the handle values with ADMIN_READ permission. If the query
    requests a specific handle value via the value index and the value
    does not have PUBLIC_READ permission, the server should accept the
    request (and authenticate the client) even if the request has its
    PO flag set.
 
    If a query consists of a non-empty <IndexList> but an empty
    <TypeList>, the server should only return those handle values whose
    indexes are listed in the <IndexList>. Likewise, if a query
    consists of non-empty <TypeList> but an empty <IndexList>, the
    server should only return those handle values whose data types are
    listed in the <TypeList>.
 
    When both <IndexList> and <TypeList> fields are non-empty, the
    server should return all handle values whose indexes are listed in
    the <IndexList> AND all handle values whose data types are listed
    in the <TypeList>.
 
 
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 3.2.2  Successful Query Response
 
    The Message Header of any query response must set its <OpCode> to
    OC_RESOLUTION. Successful query response must set its
    <ResponseCode> to RC_SUCCESS.
 
    The message body of the successful query response is defined as
    follows:
 
      <Message Body of Successful Query Response> ::= [<RequestDigest>]
                                                       <Handle>
                                                       <ValueList>
 
        where
 
          <RequestDigest>
          Optional field as defined in section 2.2.3.
 
          <Handle>
          A UTF8-String that specifies the handle queried by the
          client.
 
          <ValueList>
          A 4-byte unsigned integer followed by a list of handle
          values. The integer specifies the number of handle values in
          the list. The encoding of each handle value follows the
          specification given in [2] (see section 3.1). The integer is
          set to zero if there is no handle value that satisfies the
          query.
 
 3.2.3  Unsuccessful Query Response
 
    If a server cannot fulfill a client's request, it must return an
    error message. The general format for any error message from the
    server is specified in section 3.3 of this document.
 
    For example, a server must return an error message if the queried
    handle does not exist in its database. The error message will have
    an empty message body and have its <ResponseCode> set to
    RC_HANDLE_NOT_FOUND.
 
    Note that a server should NOT return an RC_HANDLE_NOT_FOUND message
    if the server is not responsible for the handle being queried for.
    It is possible that the queried handle exists but is managed by
    another handle server (under some other handle service). When this
    happens, the server should either send a service referral (see
    section 3.4) or simply return an error message with <ResponseCode>
    set to RC_SERVER_NOT_RESP.
 
 
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    The server may return an error message with <ResponseCode> set to
    RC_SERVER_BUSY if the server is too busy to process the request.
    Like RC_HANDLE_NOT_FOUND, an RC_SERVER_BUSY message also has an
    empty message body.
 
    Servers should return an RC_ACCESS_DENIED message if the request
    asks for a specific handle value (via the handle value index) that
    has neither PUBLIC_READ nor ADMIN_READ permission.
 
    A handle Server may ask its client to authenticate itself as the
    handle administrator during the resolution. This happens if any
    handle value in query has ADMIN_READ permission, but no PUBLIC_READ
    permission. Details of client authentication are described later in
    this document.
 
 3.3 Error Response from Server
 
    A handle server will return an error message if it encounters an
    error when processing a request. Any error response from the server
    must maintain the same <OpCode> (in the message header) as the one
    in the original request. Each error condition is identified by a
    unique <ResponseCode> as defined in section 2.2.2.2 of this
    document.
 
    The Message Body of an error message may be empty. Otherwise it
    consists of the following data fields (unless otherwise specified):
 
    <Message Body of Error Response from Server> ::= [<RequestDigest>]
                                                      <ErrorMessage>
                                                     [ <IndexList> ]
 
      where
 
        <RequestDigest>
        Optional field as defined in section 2.2.3.
 
        <ErrorMessage>
        A UTF8-String that explains the error.
 
        <IndexList>
         An optional field. When not empty, it consists of a 4-byte
         unsigned integer followed by a list of handle value indexes.
         The first integer indicates the number of indexes in the list.
         Each index in the list is a 4-byte unsigned integer that
         refers to a handle value that contributed to the error. An
         example would be a server that is asked to add three handle
         values with indexes 1, 2, and 3, and handle values with
         indexes 1 and 2 already exist. In this case the server could
 
 
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         return an error message with <REsponseCode> set to
         RC_VALUE_ALREADY_EXIST and add index 1 and 2 to the
         <IndexList>. Note that the server is not obligated to return
         the complete list of handle value indexes that may have caused
         the error.
 
 3.4 Service Referral
 
    A handle server may receive requests for handles that are managed
    by some other handle server or service. When this happens, the
    server has the option to either return a referral message that
    directs the client to the proper handle service, or simply return
    an error message with <ResponseCode> set to RC_SERVER_NOT_RESP.
    Service referral also happens when ownership of handles moves from
    one handle service to another. It may also be used by any local
    handle service to delegate its service into multiple service layers.
 
    The Message Header of a service referral must maintain the same
    <OpCode> as the one in the original request and set its
    <ResponseCode> to RC_SERVICE_REFERRAL.
 
    The Message Body of any service referral is defined as follows:
 
      <Message Body of Service Referral> ::= [ <RequestDigest> ]
                                               <ReferralHandle>
                                             [ <ValueList> ]
 
        where
 
          <RequestDigest>
          Optional field as defined in section 2.2.3.
 
          <ReferralHandle>
          A UTF8-String that identifies the handle (e.g. a service
          handle) that maintains the referral information (i.e., the
          service information of the handle service this refers to). If
          the <ReferralHandle> is set to "0.NA/0.NA", it is referring
          the client to the GHR.
 
          <ValueList>
          An optional field that must be empty if the <ReferralHandle>
          is provided. When not empty, it consists of a 4-byte unsigned
          integer followed by a list of HS_SITE values. The integer
          specifies the number of HS_SITE values in the list.
 
    Unlike regular query responses that may consist of handle values of
    any data type, a service referral can only have zero or more
    HS_SITE values in its <ValueList>. The <ReferralHandle> may contain
 
 
 
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    an empty UTF8-String if the HS_SITE values in the <ValueList> are
    not maintained by any handle.
 
    Care must be taken by clients to avoid any loops caused by service
    referrals. It is also the client's responsibility to authenticate
    the service information obtained from the service referral. A
    client should always use its own copy of the GHR service
    information if the <ReferralHandle> is set to "0.NA/0.NA".
 
 3.5 Client Authentication
 
    Clients are asked to authenticate themselves as handle
    administrators when querying for any handle value with ADMIN_READ
    but no PUBLIC_READ permission. Client authentication is also
    required for any handle administration requests that require
    administrator privileges. This includes adding, removing, or
    modifying handles or handle values.
 
    Client authentication consists of multiple messages exchanged
    between the client and server. Such message include the challenge
    from the server to the client to authenticate the client, the
    challenge-response from the client in response to the server's
    challenge, and the verification request and response message if
    secret key authentication takes place. Messages exchanged during
    the authentication are correlated via a unique <SessionId> assigned
    by the server. For each authentication session, the server needs to
    maintain the state information that includes the server's challenge,
    the challenge-response from the client, as well as the original
    client request.
 
    The authentication starts with a response message from the server
    that contains a challenge to the client. The client must respond to
    the challenge with a challenge-response message. The server
    validates the challenge-response either by verifying the digital
    signature inside the challenge-response, or by sending a
    verification request to another handle server, herein referred to
    as the verification server, that maintains the secret key for the
    administrator. The purpose of the challenge and the challenge-
    response is to prove to the server that the client possesses the
    private key (or the secret key) of the handle administrator. If the
    authentication fails, an error response will be sent back with the
    <ResponseCode> set to RC_AUTHEN_FAILED.
 
    Upon successful client authentication, the server must also make
    sure that the administrator is authorized for the request. If the
    administrator has sufficient privileges, the server will process
    the request and send back the result. If the administrator does not
    have sufficient privileges, the server will return an error message
    with <ResponseCode> set to RC_NOT_AUTHORIZED.
 
 
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    The following sections provides details of each message exchanged
    during the authentication process.
 
 3.5.1  Challenge from Server to Client
 
    The Message Header of the CHALLENGE must keep the same <OpCode> as
    the original request and set the <ResponseCode> to RC_AUTH_NEEDED.
    The server must assign a non-zero unique <SessionId> in the Message
    Envelope to keep track of the authentication. It must also set the
    RD flag of the <OpFlag> (see section 2.2.2.3) in the Message Header,
    regardless of whether the original request had the RD bit set or
    not.
 
    The Message Body of the server's CHALLENGE is defined as follows:
 
      <Message Body of Server's Challenge> ::=  <RequestDigest>
                                                <Nonce>
        where
 
          <RequestDigest>
          Message Digest of the request message, as defined in section
          2.2.3.
 
          <Nonce>
          A 4-byte unsigned integer followed by a random string
          generated by the server via a secure random number generator.
          The integer specifies the number of octets in the random
          string. The size of the random string should be no less than
          20 octets.
 
    Note that the server will not sign the challenge if the client did
    not request the server to do so. If the client worries about
    whether it is speaking to the right server, it may ask the server
    to sign the <Challenge>. If the client requested the server to sign
    the <Challenge> but failed to validate the server's signature, the
    client should discard the server's response and reissue the request
    to the server.
 
 3.5.2  Challenge-Response from Client to Server
 
    The Message Header of the CHALLENGE_RESPONSE must set its <OpCode>
    to OC_CHALLENGE_RESPONSE and its <ResponseCode> to 0. It must also
    keep the same <SessionId> (in the Message Envelope) as specified in
    the challenge from the server.
 
    The Message Body of the CHALLENGE_RESPONSE request is defines as
    follows:
 
 
 
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      <Message Body of CHALLENGE_RESPONSE> ::=  <AuthenticationType>
                                                <KeyHandle>
                                                <KeyIndex>
                                                <ChallengeResponse>
 
        where
 
          <AuthenticationType>
           A UTF8-String that identifies the type of authentication key
           used by the client. For example, the field is set to
           "HS_SECKEY" when the client choose to use a secret key for
           its authentication. The field is set to "HS_PUBKEY" if a
           public key is used instead.
 
           <KeyHandle>
           A UTF8-String that identifies the handle that holds the
           public or secret key of the handle administrator.
 
           <KeyIndex>
           A 4-byte unsigned integer that specifies the index of the
           handle value (of the <KeyHandle>) that holds the public or
           secret key of the administrator.
 
           <ChallengeResponse>
           Contains either the Message Authentication Code (MAC) or the
           digital signature over the challenge from the server. If the
           <AuthenticationType> is "HS_SECKEY", the <ChallengeResponse>
           consists of an octet followed by the MAC. The octet
           identifies the algorithm used to generate the MAC. For
           example, if the first octet is set to 0x01, the MAC is
           generated by
 
             MD5_Hash(<SecretKey> + <ServerChallenge> + <SecretKey>)
 
           where the <SecretKey> is the administrator's secret key
           referenced by the <KeyHandle> and <KeyIndex>. The
           <ServerChallenge> is the Message Body portion of the
           server's challenge. If the first octet in the
           <ChallengeResponse> is set to 0x02, the MAC is generated
           using
 
             SHA-1_Hash(<SecretKey> + <ServerChallenge> + <SecretKey>)
 
           A more secure approach is to use HMAC [17] for the
           <ChallengeResponse>. The HMAC can be generated using the
           <SecretKey> and <ServerChallenge>. A <ChallengeResponse>
           with its first octet set to 0x11 indicates that the HMAC
           is generated using the MD5 algorithm. Likewise, a
           <ChallengeResponse> with its first octet set to 0x12
 
 
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           inditates that the HMAC is generated using the SHA-1
           algorithm.
 
           If the <AuthenticationType> is "HS_PUBKEY", the
           <ChallengeResponse> contains the digital signature over the
           Message Body portion of the server's challenge. The
           signature is generated in two steps: First, a one-way hash
           value is computed over the blob that is to be signed.
           Second, the hash value is signed using the private key.
           The signature consists of a UTF8-String that specifies the
           digest algorithm used for the signature, followed by the
           signature over the server's challenge. The <KeyHandle> and
           <KeyIndex> refers to the administrator's public key that can
           be used to verify the signature.
 
    Handle administrators are defined in terms of HS_ADMIN values
    assigned to the handle. Each HS_ADMIN value defines the set of
    privileges granted to the administrator. It also provides the
    reference to the authentication key that can be used to
    authenticate the administrator. The reference can be made directly
    if the <AdminRef> field of the HS_ADMIN value refers to the handle
    value that holds the authentication key. Indirect reference to the
    authentication key can also be made via administrator groups. In
    this case, the <AdminRef> field may refer to a handle value of type
    HS_VLIST. An HS_VLIST value defines an administrator group via a
    list of handle value references, each of which refers to the
    authentication key of a handle administrator.
 
    For handles with multiple HS_ADMIN values, the server will have to
    check each of those with sufficient privileges to see if its
    <AdminRef> field matches the <KeyHandle> and <KeyIndex>. If no
    match is found, but there are administrator groups defined, the
    server must check if the <KeyHandle> and <KeyIndex> belong to any
    of the administrator groups that have sufficient privileges. An
    administrator group may contain another administrator group as a
    member. Servers must be careful to avoid infinite loops when
    navigating these groups.
 
    If the <KeyHandle> and <KeyIndex> are not referenced by any of the
    HS_ADMIN values, or the administrator group that has sufficient
    privileges, the server will return an error message with
    <ResponseCode> set to RC_NOT_AUTHORIZED. Otherwise, the server will
    continue to authenticate the client as follows:
 
    If the <AuthenticationType> is "HS_PUBKEY", the server will
    retrieve the administrator's public key based on the <KeyHandle>
    and <KeyIndex>. The public key can be used to verify the
    <ChallengeResponse> against the server's <Challenge>. If the
    <ChallengeResponse> matches the <Challenge>, the server will
 
 
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    continue to process the original request and return the result.
    Otherwise, the server will return an error message with
    <ResponseCode> set to RC_AUTHENTICATION_FAILED.
 
    If the <AuthenticationType> is "HS_SECKEY", the server will have to
    send a verification request to the verification server; that is,
    the handle server that manages the handle referenced by the
    <KeyHandle>. The verification request and its response are defined
    in the following sections. The verification server will verify the
    <ChallengeResponse> against the <Challenge> on behalf of the handle
    server.
 
 3.5.3  Challenge-Response Verification-Request
 
    The message header of the VERIFICATION_REQUEST must set its
    <OpCode> to OC_VERIFY_CHALLENGE and the <ResponseCode> to 0.
 
    The message body of the Verification-Request is defined as follows:
 
 
       <Message Body of VERIFICATION_REQUEST> ::=  <KeyHandle>
                                                  <KeyIndex>
                                                  <Challenge>
                                                  <ChallengeResponse>
 
        where
 
          <KeyHandle>
          A UTF8-String that refers to the handle that holds the
          secret key of the administrator.
 
          <KeyIndex>
          A 4-byte unsigned integer that is the index of the handle
          value that holds the secret key of the administrator.
 
          <Challenge>
          The message body of the server's challenge, as described in
          section 3.5.1.
 
          <ChallengeResponse>
          The <ChallengeResponse> from the client in response to
          the server's <Challenge>, as defined in section 3.5.2.
 
    Any Challenge-Response Verification-Request must set its CT bit in
    the message header. This is to ensure that the verification server
    will sign the Verification-Response as specified in the next
    section.
 
 
 
 
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 3.5.4  Challenge-Response Verification-Response
 
    The Verification-Response tells the requesting handle server
    whether the <ChallengeResponse> matches the <Challenge> in the
    Verification-Request.
 
    The Message Header of the Verification-Response must set its
    <ResponseCode> to RC_SUCCESS whether or not the <ChallengeResponse>
    matches the <Challenge>. The RD flag in the <OpFlag> field should
    also be set (to 1) since the <RequestDigist> will be mandatory in
    the Message Body.
 
    The Message Body of the Verification-Response is defined as
    follows:
 
      <Challenge-Response Verification-Response>
                                ::= <RequestDigest>
                                    <VerificationResult>
        where
 
          <RequestDigest>
          Contains the message digest of the Verification-Request.
 
          <VerificationResult>
          An octet that is set to 1 if the <ChallengeResponse>
          matches the <Challenge>. Otherwise it must be set to
          0.
 
    The verification server may return an error with <ResponseCode> set
    to RC_AUTHEN_FAILED if it cannot perform the verification (e.g.,
    the <KeyHandle> does not exist, or the <KeyHandle> and <KeyIndex>
    refer to an invalid handle value). When this happens, the server
    that performs the client authentication should relay the same error
    message back to the client.
 
 3.6 Handle Administration
 
    The handle system protocol supports a set of handle administration
    functions that include adding, deleting, and modifying handles or
    handle values. Before fulfilling any administration request, the
    server must authenticate the client as the handle administrator
    that is authorized for the administrative operation. Handle
    administration can only be carried out by the primary handle
    server.
 
 
 
 
 
 
 
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 3.6.1  Add Handle Value(s)
 
    Clients add values to existing handles by sending ADD_VALUE
    requests to the responsible handle server. The Message Header of
    the ADD_VALUE request must set its <OpCode> to OC_ADD_VALUE.
 
    The Message Body of the ADD_VALUE request is encoded as follows:
 
      <Message Body of ADD_VALUE Request> ::=  <Handle>
                                               <ValueList>
 
        where
 
          <Handle>
          A UTF8-String that specifies the handle.
 
          <ValueList>
          A 4-byte unsigned integer followed by a list of handle values.
          The integer indicates the number of handle values in the list.
 
    The server that receives the ADD_VALUE request must first
    authenticate the client as the administrator with the ADD_VALUE
    privilege. Upon successful authentication, the server will proceed
    to add each value in the <ValueList> to the <Handle>. If successful,
    the server will return an RC_SUCCESS message to the client.
 
    Each ADD_VALUE request must be carried out as a transaction. If
    adding any value in the <ValueList> raises an error, the entire
    operation must be rolled back. For any failed ADD_VALUE request,
    none of the values in the <ValueList> should be added to the
    <Handle>. The server must also send a response to the client that
    explains the error. For example, if a value in the <ValueList> has
    the same index as one of the existing handle values, the server
    will return an error message that has the <ResponseCode> set to
    RC_VALUE_ALREADY_EXISTS.
 
    ADD_VALUE requests can also be used to add handle administrators.
    This happens if the <ValueList> in the ADD_VALUE request contains
    any HS_ADMIN values. The server must authenticate the client as an
    administrator with the ADD_ADMIN privilege before fulfilling such
    requests.
 
    An ADD_VALUE request will result in an error if the requested
    handle does not exist. When this happens, the server will return an
    error message with <ResponseCode> set to RC_HANDLE_NOT_EXIST.
 
 3.6.2  Remove Handle Value(s)
 
 
 
 
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    Clients remove existing handle values by sending REMOVE_VALUE
    requests to the responsible handle server. The Message Header of
    the REMOVE_VALUE request must set its <OpCode> to OC_REMOVE_VALUE.
 
    The Message Body of any REMOVE_VALUE request is encoded as follows:
 
      <Message Body of REMOVE_VALUE Request> ::=  <Handle>
                                                  <IndexList>
 
        where
 
          <Handle>
          A UTF8-String that specifies the handle whose value(s) needs
          to be removed.
 
          <IndexList>
          A 4-byte unsigned integer followed by a list of handle value
          indexes. Each index refers to a handle value to be removed
          from the <Handle>. The integer specifies the number of
          indexes in the list. Each index is also encoded as a 4-byte
          unsigned integer.
 
    The server that receives the REMOVE_VALUE request must first
    authenticate the client as the administrator with the REMOVE VALUE
    privilege. Upon successful authentication, the server will proceed
    to remove the handle values specified in the <IndexList> from the
    <Handle>. If successful, the server will return an RC_SUCCESS
    message to the client.
 
    Each REMOVE_VALUE request must be carried out as a transaction. If
    removing any value specified in the <IndexList> raises an error,
    the entire operation must be rolled back. For any failed
    REMOVE_VALUE request, none of values referenced in the <IndexList>
    should be removed from the <Handle>. The server must also send a
    response to the client that explains the error. For example,
    attempts to remove any handle value with neither PUB_WRITE nor
    ADMIN_WRITE permission will result in an RC_ACCESS_DENIED error.
    Note that a REMOVE_VALUE request asking to remove a non-existing
    handle value will not be treated as an error.
 
    REMOVE_VALUE requests can also be used to remove handle
    administrators. This happens if any of the indexes in the
    <IndexList> refer to an HS_ADMIN value. Servers must authenticate
    the client as an administrator with the REMOVE_ADMIN privilege
    before fulfilling such requests.
 
 3.6.3  Modify Handle Value(s)
 
 
 
 
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    Clients can make modifications to an existing handle value by
    sending MODIFY_VALUE requests to the responsible handle server. The
    Message Header of the MODIFY_VALUE request must set its <OpCode> to
    OC_MODIFY_VALUE.
 
    The Message Body of any MODIFY_VALUE request is defined as follows:
 
      <Message Body of MODIFY_VALUE Response> ::= <Handle>
                                                  <ValueList>
 
        where
 
          <Handle>
          A UTF8-String that specifies the handle whose value(s) needs
          to be modified.
 
          <ValueList>
          A 4-byte unsigned integer followed by a list of handle
          values. The integer specifies the number of handle values in
          the list. Each value in the <ValueList> specifies a handle
          value that will replace the existing handle value with
          the same index.
 
    The server that receives the MODIFY_VALUE request must first
    authenticate the client as an administrator with the MODIFY_VALUE
    privilege. Upon successful authentication, the server will proceed
    to replace those handle values listed in the <ValueList>, provided
    each handle value has PUB_WRITE or ADMIN_WRITE permission. If
    successful, the server must notify the client with an RC_SUCCESS
    message.
 
    Each MODIFY_VALUE request must be carried out as a transaction. If
    replacing any value listed in the <ValueList> raises an error, the
    entire operation must be rolled back. For any failed MODIFY_VALUE
    request, none of values in the <ValueList> should be replaced. The
    server must also return a response to the client that explains the
    error. For example, if a MODIFY_VALUE request asks to remove a
    handle value that has neither PUB_WRITE nor ADMIN_WRITE permission,
    the server must return an error message with the <ResponseCode> set
    to RC_ACCESS_DENIED. Any MODIFY_VALUE request to replace non-
    existing handle values is also treated as an error. In this case,
    the server will return an error message with <ResponseCode> set to
    RC_VALUE_NOT_FOUND.
 
    MODIFY_VALUE requests can also be used to update handle
    administrators. This happens if both the values in the <ValueList>
    and the value to be replaced are HS_ADMIN values. Servers must
    authenticate the client as an administrator with the MODIFY_ADMIN
    privilege before fulfilling such request. It is an error to replace
 
 
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    a non-HS_ADMIN value with an HS_ADMIN value. In this case, the
    server will return an error message with <ResponseCode> set to
    RC_VALUE_INVALID.
 
 3.6.4  Create Handle
 
    Clients can create new handles by sending CREATE_HANDLE requests to
    the responsible handle server. The Message Header of any
    CREATE_HANDLE request must set its <OpCode> to OC_CREATE_HANDLE.
 
    The Message Body of any CREATE_HANDLE request is defined as
    follows:
 
      <Message Body of CREATE_HANDLE Response> ::= <Handle>
                                                   <ValueList>
 
        where
 
          <Handle>
          A UTF8-String that specifies the handle.
 
          <ValueList>
          A 4-byte unsigned integer followed by a list of handle
          values. The integer indicates the number of handle values in
          the list. The <ValueList> should at least include one
          HS_ADMIN value that defines the handle administrator.
 
    Only naming authority administrators with the CREATE_HANDLE
    privilege are allowed to create new handles under the naming
    authority. The server that receives a CREATE_HANDLE request must
    authenticate the client as the administrator of the corresponding
    naming authority handle and make certain that the administrator is
    authorized to create handles under the naming authority. This is
    different from the ADD_VALUE request where the server authenticates
    the client as an administrator of the handle. Upon successful
    authentication, the server will proceed to create the new handle
    and add each value in the <ValueList> to the new <Handle>. If
    successful, the server will return an RC_SUCCESS message to the
    client.
 
    Each CREATE_HANDLE request must be carried out as a transaction. If
    any part of the CREATE_HANDLE process fails, the entire operation
    can be rolled back. For example, if the server fails to add values
    in the <ValueList> to the new handle, it must return an error
    message without creating the new handle. Any CREATE_HANDLE request
    that asks to create a handle that already exists will be treated as
    an error. In this case, the server will return an error message
    with the <ResponseCode> set to RC_HANDLE_ALREADY_EXIST.
 
 
 
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    CREATE_HANDLE requests can also be used to create naming
    authorities. Naming authorities are created as naming authority
    handles at the GHR. Before creating a new naming authority handle,
    the server must authenticate the client as the administrator of the
    parent naming authority. Only administrators with the CREATE_NA
    privilege are allowed to create any sub-naming authority. Root
    level naming authorities may be created by the administrator of the
    root handle "0.NA/0.NA".
 
 3.6.5  Delete Handle
 
    Clients delete existing handles by sending DELETE_HANDLE requests
    to the responsible handle server. The Message Header of the
    DELETE_HANDLE request must set its <OpCode> to OC_DELETE_HANDLE.
 
    The Message Body of any DELETE_HANDLE request is defined as
    follows:
 
      <Message Body of DELETE_HANDLE Request> ::= <Handle>
 
        where
 
          <Handle>
          A UTF8-String that specifies the handle.
 
    The server that receives the DELETE_HANDLE request must first
    authenticate the client as the administrator with the DELETE_HANDLE
    privilege. Upon successful authentication, the server will proceed
    to delete the handle along with any handle values assigned to the
    handle. If successful, the server will return an RC_SUCCESS message
    to the client.
 
    Each DELETE_HANDLE request must be carried out as a transaction. If
    any part of the DELETE_HANDLE process fails, the entire operation
    must be rolled back. For example, if the server fails to remove any
    handle values assigned to the handle (before deleting the handle),
    it must return an error message without deleting the handle. This
    may happen if the handle contains a value that has neither
    PUB_WRITE nor ADMIN_WRITE permission. In this case, the server will
    return an error message with the <ResponseCode> set to
    RC_PERMISSION_DENIED. A DELETE_HANDLE request that asks to delete a
    non-existing handle will also be treated as an error. The server
    will return an error message with the <ResponseCode> set to
    RC_HANDLE_NOT_EXIST.
 
    DELETE_HANDLE requests can also be used to delete naming
    authorities. This is achieved by deleting the corresponding naming
    authority handle on the GHR. Before deleting a naming authority
    handle, the server must authenticate the client as the
 
 
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    administrator of the naming authority handle. Only administrators
    with the DELETE_NA privilege are allowed to delete the naming
    authority. Root level naming authorities may be deleted by the
    administrator of the root handle "0.NA/0.NA".
 
 3.7 Naming Authority (NA) Administration
 
    The Handle System manages naming authorities via naming authority
    handles. Naming authority handles are managed by the GHR. Clients
    can change the service information of any naming authority by
    changing the HS_SITE values assigned to the corresponding naming
    authority handle. Creating or deleting naming authorities is done
    by creating or deleting the corresponding naming authority handles.
    Root level naming authorities may be created or deleted by the
    administrator of the root handle "0.NA/0.NA". Non-root-level naming
    authorities may be created by the administrator of its parent
    naming authority.
 
    For example, the administrator of the naming authority handle
    "0.NA/10" may create the naming authority "10.1000" by sending a
    CREATE_HANDLE request to the GHR to create the naming authority
    handle "0.NA/10.1000". Before fulfilling the request, the server at
    the GHR must authenticate the client as the administrator of the
    parent naming authority, that is, the administrator of the naming
    authority handle "0.NA/10". The server must also make sure that the
    administrator has the NA_CREATE privilege.
 
    The handle protocol also allows clients to list handles or sub-
    naming authorities under a naming authority. Details of these
    operations are described in the following sections.
 
 3.7.1  List Handle(s) under a Naming Authority
 
    Clients send LIST_HANDLE requests to handle servers to get a list
    of handles under a naming authority. The Message Header of the
    LIST_HANDLE request must set its <OpCode> to OC_LIST_HANDLE.
 
    The Message Body of any LIST_HANDLE request is defined as follows:
 
      <Message Body of LIST_HANDLE Request> ::= <NA_Handle>
 
        where
 
          <NA_Handle>
          A UTF8-String that specifies the naming authority handle.
 
    To obtain a complete list of the handles, the request must be sent
    to every handle server listed in any one of the service sites of
    the responsible handle service. Each server within the service site
 
 
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    will return its own list of handles under the naming authority. The
    Message Body of a successful LIST_HANDLE response (from each handle
    server) is defined as follows:
 
      <Message Body of LIST_HANDLE Response>  ::=  <Num_Handles>
                                                   <HandleList>
        where
 
          <Num_Handles>
          Number of handles (managed by the handle server) under the
          naming authority.
 
          <HandleList>
          A list of UTF8-Strings, each of which identify a handle under
          the naming authority.
 
    The LIST_HANDLE request may potentially slow down the overall
    system performance. A handle service (or its service site) has the
    option whether or not to support such request. The server will
    return an RC_OPERATION_DENIED message if LIST_HANDLE is not
    supported. The server that receives a LIST_HANDLE request should
    authenticate the client as a naming authority administrator with
    the LIST_HANDLE privilege before fulfilling the request.
 
 3.7.2  List Sub-Naming Authorities under a Naming Authority
 
    Clients send LIST_NA requests to handle servers to get a list of
    sub-naming authorities under a naming authority. The Message Header
    of the LIST_NA request must set its <OpCode> to OC_LIST_NA.
 
    The Message Body of any LIST_NA request is defined as follows:
 
      <Message Body of LIST_HANDLE Request> ::= <NA_Handle>
 
        where
 
          <NA_Handle>
          A UTF8-String that specifies the naming authority handle.
 
    To obtain a complete list of the sub-naming authorities, the
    request must be sent to every handle server listed in any one of
    the service sites of the GHR. Each server within the service site
    will return its own list of sub-naming authority handles under the
    given naming authority. The Message Body of a successful LIST_NA
    response (from each handle server) is defined as follows:
 
      <Message Body of LIST_HANDLE Response> ::=  <Num_Handles>
                                                  <HandleList>
        where
 
 
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          <Num_Handles>
          Number of handles (managed by the handle server) under the
          naming authority.
 
          <HandleList>
          A list of UTF8-Strings, each of which identifies a sub-
          naming authority user-specified naming authority.
 
    LIST_NA requests must be sent to servers under the GHR which
    manages all the naming authority handles. The LIST_NA request may
    potentially slow down the overall system performance, especially
    the GHS. A server (or service sites) under the GHR has the option
    whether or not to support such requests. The server will return an
    RC_OPERATION_DENIED message if LIST_NA is not supported. The server
    that receives a LIST_HANDLE request should authenticate the client
    as a naming authority administrator with the LIST_NA privilege
    before fulfilling the request.
 
 3.8 Session and Session Management
 
    Sessions are used to allow sharing of authentication information or
    network resources among multiple protocol operations. For example,
    a naming authority administrator may authenticate itself once
    through the session setup, and then register multiple handles under
    the session.
 
    A client may ask the server to establish a session key and use it
    for subsequent requests. A session key is a secret key that is
    shared by the client and server. It can be used to authenticate or
    encrypt any message exchanged under the session. A session is
    encrypted if every message exchanged within the session is
    encrypted using the session key.
 
    Sessions may be established as the result of an explicit
    OC_SESSION_SETUP request from a client. A server may also setup a
    session automatically when multiple message exchanges are expected
    to fulfill a request. For example, the server will establish a
    session automatically if it receives a CREATE_HANDLE request that
    requires client authentication.
 
    Every session is identified by a non-zero Session ID that appears
    in the Message Header. Servers are responsible for generating a
    unique Session ID for each outstanding session. Each session may
    have a set of state information associated with it. The state
    information may include the session key, the information obtained
    from client authentication, as well as any communication options.
    Servers and clients are responsible for keeping the state
    information in sync until the session is terminated.
 
 
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    A session may be terminated with an OC_SESSION_TERMINATE request
    from the client. Servers may also terminate a session that has been
    idle for a significant amount of time.
 
 3.8.1  Session Setup Request
 
    Clients establish a session with a handle server with a
    SESSION_SETUP request. A SESSION_SETUP request can also be used to
    update any state information associated to an existing session. The
    Message Header of the SESSION_SETUP request must have its <OpCode>
    set to OC_SESSION_SETUP and <ResponseCode> to 0.
 
    The Message Body of any SESSION_SETUP request is defined as
    follows:
 
      <SESSION_SETUP Request Message Body> ::= <SessionAttributes>
 
        where
 
          <SessionAttributes>
          A 4-byte unsigned integer followed by a list of session
          attributes. The integer indicates the number of session
          attributes in the list. Possible session attributes include
          the <HS_SESSION_IDENTITY>, the <HS_SESSION_TIMEOUT>, and the
          <HS_SESSION_KEY_EXCHANGE>. Each of these attributes is
          defined as follows:
 
            <HS_SESSION_IDENTITY> ::= <Key>
                                      <Handle>
                                      <ValueIndex>
              where
 
                <Key>
                A UTF-8 string constant "HS_SESSION_IDENTITY".
 
                <Handle>
                <ValueIndex>
                A UTF-8 string followed by a 4-byte unsigned integer
                that specifies the handle and the handle value used for
                client authentication. It must refer to a handle value
                that contains the public key of the client. The public
                key is used by the server to authenticate the client.
 
            <HS_SESSION_KEY_EXCHANGE> ::= <Key>
                                          <KeyExchangeData>
              where
 
                <Key>
 
 
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                A UTF-8 string constant "HS_SESSION_KEY_EXCHANGE".
 
                <KeyExchangeData>
                One of the these tuples: <ClientCipher KeyExchange>,
                <HdlCipher KeyExchange>, or <ServerCipher KeyExchange>.
                Each of these tuples is defined as follows:
 
                  <ClientCipher KeyExchange> ::= <Key>
                                                 <PubKey>
                    where
 
                      <Key>
                      A UTF-8 string constant "CLIENT_CIPHER".
 
                      <PubKey>
                      A public key provided by the client and used by
                      the server to encrypt the session key.
 
                  <HdlCipher KeyExchange> ::= <Key>
                                              <ExchangeKeyHdl>
                                              <ExchangeKeyIndex>
                    where
 
                      <Key>
                      A UTF-8 string constant "HDL_CIPHER".
 
                      <ExchangeKeyHdl>
                      <ExchangeKeyIndex>
                      A UTF-8 string followed by a 4-byte unsigned
                      integer. The <ExchangeKeyHdl> and
                      <ExchangeKeyIndex> refers to a handle value used
                      for session key exchange. The handle value must
                      contain the public key of the client. The public
                      key will be used by the server to encrypt the
                      session key before sending it to the client.
 
                  <ServerCipher KeyExchange> ::= <Key>
 
                    where
 
                      <Key>
                      A UTF-8 string constant "SERVER_CIPHER". This
                      tells the server that the client will be
                      responsible for generating the session key. The
                      server will have to provide its public key in the
                      response message and set the <ResponseCode> to
                      RC_SESSION_EXCHANGEKEY. The client can use the
                      server's public key to encrypt the session key
                      and send it to the server via a subsequent
 
 
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                      SESSION_EXCHANGEKEY request.
 
                  <DiffieHellman KeyExchange> ::= <Key>
                                                  <DHParams>
                    where
 
                      <Key>
                      A UTF-8 string constant "DIFFIE_HELLMAN"
 
                      <DHParams>
                      The values used as input to the Diffie-Hellman
                      algorithm. It consists of three big integers of
                      variable length. Each big integer is encoded in
                      terms of a 4-byte unsigned integer followed by an
                      octet string. The octet string contains the big
                      integer itself. The 4-byte unsigned integer
                      specifies the number of octets of the octet
                      string.
 
 
          <HS_SESSION_TIMEOUT> ::=  <Key>
                                    <TimeOut>
            where
 
              <Key>
              A UTF-8 string constant "HS_SESSION_TIMEOUT".
 
              <TimeOut>
              A 4-byte unsigned integer that specifies the desired
              duration of the session in number of seconds.
 
    Note that it should be treated as an error if the same session
    attribute is listed multiple times in the <SessionAttribute> field.
    When this happens, the server should return an error message with
    <ResponseCode> set to RC_PROTOCOL_ERROR.
 
    A SESSION_SETUP_REQUEST can be used to change session attributes of
    any established session. This happens if the <SessionId> is non-
    zero and matches one of the established sessions. Care must be
    taken by the server to prevent any unauthorized request from
    changing the session attributes. For example, an encrypted session
    may only be changed into an unencrypted session by a
    SESSION_SETUP_REQUEST with appropriate MAC in its Message
    Credential.
 
 3.8.2  Session Setup Response
 
    The Message Header of the SESSION_SETUP response must set its
    <OpCode> to OC_SESSION_SETUP. The <ResponseCode> of the
 
 
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    SESSION_SETUP response varies according to the SESSION_SETUP
    request. It must be set to RC_SUCCESS if the SESSION_SETUP request
    is successful and the server does not expect a session key to be
    returned by the client.
 
    The Message Body of the SESSION_SETUP response is empty unless the
    request is asking for <HS_SESSION_KEY_EXCHANGE>. In this case, the
    Message Body of the SESSION_SETUP response may contain the
    encrypted session key from the server, or the server' public key,
    to be used for session key exchange. The exact format depends on
    the content of the <HS_SESSION_KEY_EXCHANGE> in the SESSION_SETUP
    request. If <ClientCipher KeyExchange> or <HdlCipher KeyExchange>
    is given in the SESSION_SETUP request, the Message Body of the
    SESSION_SETUP response will contain the encrypted session key from
    the server and is defined as follows:
 
      <Message Body of SESSION_SETUP Response>
                                        ::= <RequestDigest>
                                            <EncryptedSessionKey>
                                          [ <EncryptionAlgorithm> ]
        where
 
          <RequestDigest>
          Message digest of the SESSION_SETUP request as specified in
          section 2.2.3.
 
          <EncryptedSessionKey>
          Session key encrypted using the public key provided in the
          SESSION_SETUP request. The session key is a randomly
          generated octet string from the server. The server will only
          return the <EncryptedSessionKey> if the <KeyExchangeData> in
          the SESSION_SETUP request provides the public key from the
          client.
 
          <EncryptionAlgorithm>
          (optional) UTF-8 string that identifies the encryption
          algorithm used by the session key.
 
 
    If <ServerCipher KeyExchange> is given in the SESSION_SETUP
    request, the server must provide its public key in the
    SESSION_SETUP response. The public key can be used by the client in
    a subsequent SESSION_EXCHANGEKEY request (defined below) for
    session key exchange. In this case, the Message Header of the
    SESSION_SETUP response must set its <ResponseCode> to
    RC_SESSION_EXCHANGEKEY. The Message Body of the SESSION_SETUP
    response must include the server's public key and is defined as
    follows:
 
 
 
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      <Message Body of SESSION_SETUP response>
                              ::= <RequestDigest>
                                  <Public Key for Session Key Exchange>
 
        where
 
          <RequestDigest>
          Message digest of the SESSION_SETUP request as specified in
          section 2.2.3.
 
          <Public Key for Session Key Exchange>
          Public key from the server to be used for session key
          exchange. It is encoded in the same format as the <PublicKey>
          record in the HS_SITE value (see section 3.2.2 in [2]).
 
 3.8.3  Session Key Exchange
 
    If the <ResponseCode> of a SESSION_SETUP response is
    RC_SESSION_EXCHANGEKEY, the client is responsible for generating
    the session key and sending it to the server. In this case, the
    client can generate a session key, encrypt it with the public key
    provided by the server in the SESSION_SETUP response, and send the
    encrypted session key to the server in a SESSION_EXCHANGEKEY
    request.
 
    The Message Header of the SESSION_EXCHANGEKEY request must set its
    <OpCode> to OC_SESSION_EXCHANGEKEY and its <ResponseCode> to 0. The
    Message Body of the SESSION_EXCHANGEKEY request is defined as
    follows:
 
      <Message Body of OC_SESSION_EXCHANGEKEY>
                      ::=   <Encrypted Session Key>
                          [ <EncryptionAlgorithm> ]
 
        where
 
          <EncryptedSessionKey>
          Session key encrypted using the public key provided in the
          SESSION_SETUP response. The session key is a randomly
          generated octet string by the client.
 
          <EncryptionAlgorithm>
          (optional) UTF-8 string that identifies the encryption
          algorithm used by the session key.
 
    During the session key exchange, the server receiving the exchange
    key or session key has the responsibility to make sure that the key
    meets the security requirements defined in its local policy. If the
    server considers the key being volunable, it must return an error
 
 
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    message to the client with <ResponseCode> set to
    RC_SESSION_KEY_INVALID.
 
 3.8.4  Session Termination
 
    Clients can terminate a session with a SESSION_TERMINATE request.
    The Message Header of a SESSION_TERMINATE request must have its
    <OpCode> set to OC_SESSION_TERMINATE and its <ResponseCode> to 0.
    The message body of any SESSION_TERMINATE request must be empty.
 
    The server must send a SESSION_TERMINATE response to the client
    after the session is terminated. The server should only terminate
    the session after it has finished processing all the requests
    (under the session) that were submitted before the Session
    Termination request.
 
    The message header of the SESSION_TERMINATE response must set its
    <OpCode> to OC_SESSION_TERMINATE. A successful SESSION_TERMINATE
    response must have its <ResponseCode> set to RC_SUCCESS, and an
    empty message body.
 
 4. Implementation Guidelines
 
 4.1 Server Implementation
 
    The optimal structure for any handle server will depend on the host
    operating system. This section only addresses those implementation
    considerations that are common to most handle servers.
 
    A good server implementation should allow easy configuration or
    fine-tuning. A suggested list of configurable items includes the
    server's network interface(s) (e.g., IP address, port number,
    etc.), the number of concurrent processes/threads allowed, time-out
    intervals for any TCP connection and/or authentication process, re-
    try policy under UDP connection, policies on whether to support
    recursive service, case-sensitivity for ASCII characters, and
    different levels of transaction logging, etc.
 
    All handle server implementations must support all the handle data
    types as defined in the "Handle System Namespace and Service
    Definition" [2]. They should also be able to store handle values of
    any application defined data type.
 
    A handle server must support multiple concurrent activities,
    whether they are implemented as separate processes or threads in
    the host's operating system, or multiplexed inside a single name
    server program. A handle server should not block the service of UDP
    requests while it waits for TCP data or other query activities.
    Similarly, a handle server should not attempt to provide recursive
 
 
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    service without processing such requests in parallel, though it may
    choose to serialize requests from a single client, or to regard
    identical requests from the same client as duplicates.
 
 4.2 Client Implementation
 
    Clients should be prepared to receive handle values of any data
    type. Clients may choose to implement a callback interface to allow
    new modules or plug-ins to be added to support any application-
    defined data types.
 
    Clients that follow service referrals or handle aliases must avoid
    falling into an infinite loop. They should not repeatedly contact
    the same server for the same request with the same target entry. A
    client may choose to use a counter that is incremented each time it
    follows a service referral or handle alias. There should be a
    configurable upper limit to the counter to control the levels of
    service referrals or handle aliases followed by the client.
 
    Clients that provide some caching can expect much better
    performance than those that don't. Client implementations should
    always consider caching the service information associated with a
    naming authority. This will reduce the number of roundtrips for
    subsequent handle requests under the same naming authority.
 
 5. Security Considerations
 
    The overall Handle System security considerations are discussed in
    "Handle System Overview" [1] and that discussion applies equally to
    this document. Security considerations regarding the Handle System
    data model and service model are discussed in "Handle System
    Namespace and Service Definition" [2].
 
    For efficiency, the handle protocol includes a simple challenge-
    response authentication protocol for basic client authentication.
    Handle servers are free to provide additional authentication
    mechanisms (e.g., SASL) as needed. Details of this will be
    discussed in a separate document.
 
    Data integrity under the handle protocol is achieved via the
    server's digital signature. Care must be taken to protect the
    server's private key from any impersonation attack. Any change to
    the server's public key pair must be registered (in terms of
    service information) with the GHR.
 
 References and Bibliography
 
    [1] S. Sun, L. Lannom, "Handle System Overview", IETF draft, work
    in progress
 
 
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    [2] S. Sun, S. Reilly, L. Lannom, "Handle System Namespace and
    Service Definition", IETF draft, work in progress
 
    [3]  F. Yergeau, "UTF-8, A Transform Format for Unicode and
    ISO10646", RFC2044, October 1996
 
    [4] A. Freier, P. Karlton, P. Kocher "The SSL Protocol Version 3.0"
 
    [5] RSA Laboratories, "Public-Key Cryptography Standard PKCS#7"
    http://www.rsasecurity.com/rsalabs/pkcs/
 
    [6] U.S. Federal Information Processing Standard: Digital Signature
    Standard.
 
    [7] R. Housley, "Cryptographic Message Syntax (CMS) Algorithms",
    RFC3370, August, 2002
 
    [8] R. Braden, "FTP DATA COMPRESSION", RFC468, March 8, 1973
 
    [9] R. Rivest, "The MD5 Message-Digest Algorithm", RFC1321, April
    1992.
 
    [10] NIST, FIPS PUB 180-1: Secure Hash Standard, April 1995.
 
    [11] D. Cohen, "On Holy Wars and a Plea for Peace", Internet
    Experiment, Note IEN 137, 1 April 1980.
 
    [12] H. Balakrishnan and S. Seshan. "The Congestion Manager", RFC
    3124, June 2001
 
    [13] R. Kahn, R. Wilensky, "A Framework for Distributed Digital
    Object Services, May 1995, http://www.cnri.reston.va.us/k-w.html
 
    [14] W. Polk, R. Housley, L. Bassham, "Algorithms and Identifiers
    for the Internet X.509 Public Key Infrastructure Certificate and
    Certificate Revocation List (CRL) Profile", RFC3279, April, 2002
 
    [15] R. Housley, W. Polk, W. Ford, D. Solo, "Internet X.509 Public
    Key Infrastructure Certificate and Certificate Revocation List(CRL)
    Profile", RFC3280, April, 2002
 
    [16] M. Bellare and P. Rogaway. The Exact Security of Digital
    Signatures - How to Sign with RSA and Rabin. In Advances in
    Cryptology-Eurocrypt '96, pp.399-416, Springer-Verlag, 1996.
 
    [17] H. Krawczyk, M. Bellare, R. Canetti, "HMAC: Keyed-Hashing for
    Message Authentication", RFC2104, February, 1997
 
 
 
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    [18] R. Kahn, R. Wilensky, "A Framework for Distributed Digital
    Object Services, May 1995, http://www.cnri.reston.va.us/k-w.html
 
 Author's Addresses
 
    Sam X. Sun
    Corporation for National Research Initiatives (CNRI)
    1895 Preston White Dr.  Suite 100
    Reston, VA 20191
    Phone: 703-262-5316
    Email: ssun@cnri.reston.va.us
 
    Sean Reilly
    Corporation for National Research Initiatives (CNRI)
    1895 Preston White Dr.     Suite 100
    Reston, VA 20191
    Phone: 703-620-8990
    Email: sreilly@cnri.reston.va.us
 
    Larry Lannom
    Corporation for National Research Initiatives (CNRI)
    1895 Preston White Dr.     Suite 100
    Reston, VA 20191
    Phone: 703-262-5307
    Email: llannom@cnri.reston.va.us
 
    Jason Petrone
    Corporation for National Research Initiatives (CNRI)
    1895 Preston White Dr.     Suite 100
    Reston, VA 20191
    Phone: 703-262-5340
    Email: jpetrone@cnri.reston.va.us
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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