Bundle Protocol Security Specification
draft-ietf-dtn-bpsec-22

Delay-Tolerant Networking                                     E. Birrane
Internet-Draft                                                   JHU/APL
Intended status: Experimental                                   J. Mayer
Expires: September 20, 2016                                    INSYEN AG
                                                             D. Iannicca
                                                                NASA GRC
                                                          March 19, 2016


                 Bundle Protocol Security Specification
                        draft-ietf-dtn-bpsec-01

Abstract

   This document defines a security protocol providing data integrity
   and confidentiality services for the Bundle Protocol.  Capabilities
   are provided to protect blocks in a bundle along a single path
   through a network.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 20, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Related Documents . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Key Properties  . . . . . . . . . . . . . . . . . . . . . . .   6
     2.1.  Block-Level Granularity . . . . . . . . . . . . . . . . .   6
     2.2.  Multiple Security Sources . . . . . . . . . . . . . . . .   6
     2.3.  Mixed Security Policy . . . . . . . . . . . . . . . . . .   7
     2.4.  User-Selected Ciphersuites  . . . . . . . . . . . . . . .   8
     2.5.  Deterministic Processing  . . . . . . . . . . . . . . . .   8
   3.  Security Block Definitions  . . . . . . . . . . . . . . . . .   8
     3.1.  Block Identification  . . . . . . . . . . . . . . . . . .   9
     3.2.  Block Representation  . . . . . . . . . . . . . . . . . .   9
       3.2.1.  CMS Block Type-Specific Data Fields . . . . . . . . .  10
       3.2.2.  BIB and BCB Block Type-Specific Data Fields . . . . .  10
     3.3.  Block Ordering  . . . . . . . . . . . . . . . . . . . . .  11
     3.4.  Block Integrity Block . . . . . . . . . . . . . . . . . .  12
     3.5.  Block Confidentiality Block . . . . . . . . . . . . . . .  13
     3.6.  Cryptographic Message Syntax Block  . . . . . . . . . . .  15
     3.7.  Block Interactions  . . . . . . . . . . . . . . . . . . .  16
     3.8.  Parameters and Result Fields  . . . . . . . . . . . . . .  17
     3.9.  BSP Block Example . . . . . . . . . . . . . . . . . . . .  19
   4.  Security Processing . . . . . . . . . . . . . . . . . . . . .  22
     4.1.  Canonical Forms . . . . . . . . . . . . . . . . . . . . .  22
       4.1.1.  Block Canonicalization  . . . . . . . . . . . . . . .  22
       4.1.2.  Considerations  . . . . . . . . . . . . . . . . . . .  25
     4.2.  Endpoint ID Confidentiality . . . . . . . . . . . . . . .  25
     4.3.  Bundles Received from Other Nodes . . . . . . . . . . . .  26
       4.3.1.  Receiving BCB Blocks  . . . . . . . . . . . . . . . .  26
       4.3.2.  Receiving BIB Blocks  . . . . . . . . . . . . . . . .  26
     4.4.  Receiving CMSB Blocks . . . . . . . . . . . . . . . . . .  27
     4.5.  Bundle Fragmentation and Reassembly . . . . . . . . . . .  27
     4.6.  Reactive Fragmentation  . . . . . . . . . . . . . . . . .  28
   5.  Key Management  . . . . . . . . . . . . . . . . . . . . . . .  28
   6.  Policy Considerations . . . . . . . . . . . . . . . . . . . .  28
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  29
   8.  Conformance . . . . . . . . . . . . . . . . . . . . . . . . .  29
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  30
     9.1.  Bundle Block Types  . . . . . . . . . . . . . . . . . . .  30
     9.2.  Cipher Suite Flags  . . . . . . . . . . . . . . . . . . .  30
     9.3.  Parameters and Results  . . . . . . . . . . . . . . . . .  31
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  31
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  31
     10.2.  Informative References . . . . . . . . . . . . . . . . .  32



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   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  32
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  32

1.  Introduction

   This document defines security features for the Bundle Protocol
   [BPBIS] intended for use in delay-tolerant networks, in order to
   provide Delay-Tolerant Networking (DTN) security services.

   The Bundle Protocol is used in DTNs that overlay multiple networks,
   some of which may be challenged by limitations such as intermittent
   and possibly unpredictable loss of connectivity, long or variable
   delay, asymmetric data rates, and high error rates.  The purpose of
   the Bundle Protocol is to support interoperability across such
   stressed networks.

   The stressed environment of the underlying networks over which the
   Bundle Protocol operates makes it important for the DTN to be
   protected from unauthorized use, and this stressed environment poses
   unique challenges for the mechanisms needed to secure the Bundle
   Protocol.  Furthermore, DTNs may be deployed in environments where a
   portion of the network might become compromised, posing the usual
   security challenges related to confidentiality, integrity, and
   availability.

   This document describes the Bundle Protocol Security Specification
   (BPSec), which provides security services for blocks within a bundle
   from the bundle source to the bundle destination.  Specifically,
   BPSec provides integrity and confidentiality for bundles along a path
   through a DTN.

   BPSec applies, by definition, only to those nodes that implement it,
   known as "security-aware" nodes.  There MAY be other nodes in the DTN
   that do not implement BPSec.  All nodes can interoperate with the
   exception that BPSec security operations can only happen at BPSec
   security-aware nodes.

1.1.  Related Documents

   This document is best read and understood within the context of the
   following other DTN documents:

   "Delay-Tolerant Networking Architecture" [RFC4838] defines the
   architecture for delay-tolerant networks, but does not discuss
   security at any length.






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   The DTN Bundle Protocol [BPBIS] defines the format and processing of
   the blocks used to implement the Bundle Protocol, excluding the
   security-specific blocks defined here.

   The Bundle Security Protocol [RFC6257] and Streamlind Bundle Security
   Protocol [SBSP] introduce the concepts of security blocks for
   security services.  BPSec is based off of these documents.

1.2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

   We introduce the following terminology for purposes of clarity.

   o  Source - the bundle node from which a bundle originates.

   o  Destination - the bundle node to which a bundle is ultimately
      destined.

   o  Forwarder - the bundle node that forwarded the bundle on its most
      recent hop.

   o  Intermediate Receiver, Waypoint, or "Next Hop" - the neighboring
      bundle node to which a forwarder forwards a bundle.

   o  Path - the ordered sequence of nodes through which a bundle passes
      on its way from source to destination.  The path is not
      necessarily known by the bundle, or any bundle-aware nodes.

   Figure 1 below is adapted from [BPBIS] and shows four bundle nodes
   (denoted BN1, BN2, BN3, and BN4) that reside above some transport
   layer(s).  Three distinct transport and network protocols (denoted
   T1/N1, T2/N2, and T3/N3) are also shown.















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   +---------v-|   +->>>>>>>>>>v-+     +->>>>>>>>>>v-+   +-^---------+
   | BN1     v |   | ^   BN2   v |     | ^   BN3   v |   | ^  BN4    |
   +---------v-+   +-^---------v-+     +-^---------v-+   +-^---------+
   | T1      v |   + ^  T1/T2  v |     + ^  T2/T3  v |   | ^  T3     |
   +---------v-+   +-^---------v-+     +-^---------v +   +-^---------+
   | N1      v |   | ^  N1/N2  v |     | ^  N2/N3  v |   | ^  N3     |
   +---------v-+   +-^---------v +     +-^---------v-+   +-^---------+
   |         >>>>>>>>^         >>>>>>>>>>^         >>>>>>>>^         |
   +-----------+   +------------+      +-------------+   +-----------+
   |                     |                    |                      |
   |<--  An Internet --->|                    |<--- An Internet  --->|
   |                     |                    |                      |


      Figure 1: Bundle Nodes Sitting at the Application Layer of the
                              Internet Model

   BN1 originates a bundle that it forwards to BN2.  BN2 forwards the
   bundle to BN3, and BN3 forwards the bundle to BN4.  BN1 is the source
   of the bundle and BN4 is the destination of the bundle.  BN1 is the
   first forwarder, and BN2 is the first intermediate receiver; BN2 then
   becomes the forwarder, and BN3 the intermediate receiver; BN3 then
   becomes the last forwarder, and BN4 the last intermediate receiver,
   as well as the destination.

   If node BN2 originates a bundle (for example, a bundle status report
   or a custodial signal), which is then forwarded on to BN3, and then
   to BN4, then BN2 is the source of the bundle (as well as being the
   first forwarder of the bundle) and BN4 is the destination of the
   bundle (as well as being the final intermediate receiver).

   We introduce the following security-specific DTN terminology.

   o  Security-Service - the security features supported by this
      specification: authentication, integrity, and confidentiality.

   o  Security-Source - a bundle node that adds a security block to a
      bundle.

   o  Security-Target - the portion of a bundle (e.g., the primary
      block, payload block, extension block, or entire bundle) that
      receives a security-service as part of a security-operation.

   o  Security Block - a single instance of a BPSec extension block in a
      bundle.

   o  Security-Operation - the application of a security-service to a
      specific security-target, notated as OP(security-service,



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      security-target).  For example, OP(authentication, bundle) or
      OP(confidentiality, payload).  Every security-operation in a
      bundle MUST be unique, meaning that a security-service can only be
      applied to a security-target once in a bundle.  A security-
      operation MAY be implemented by one or more security blocks.

2.  Key Properties

   The application of security services in a DTN is a complex endeavor
   that must consider physical properties of the network, policies at
   each node, and various application security requirements.  Rather
   than enumerate all potential security implementations in all
   potential DTN topologies, this specification defines a set of key
   properties of a security system.  The security primitives outlined in
   this document MUST enable the realization of these properties in a
   DTN deploying the Bundle Protocol.

2.1.  Block-Level Granularity

   Blocks within a bundle represent different types of information.  The
   primary block contains identification and routing information.  The
   payload block carries application data.  Extension blocks carry a
   variety of data that may augment or annotate the payload, or
   otherwise provide information necessary for the proper processing of
   a bundle along a path.  Therefore, applying a single level and type
   of security across an entire bundle fails to recognize that blocks in
   a bundle may represent different types of information with different
   security needs.

   Security services within this specification MUST provide block level
   granularity where applicable such that different blocks within a
   bundle may have different security services applied to them.

   For example, within a bundle, a payload might be encrypted to protect
   its contents, whereas an extension block containing summary
   information related to the payload might be integrity signed but
   otherwise unencrypted to provide certain nodes access to payload-
   related data without providing access to the payload.

2.2.  Multiple Security Sources

   The Bundle Protocol allows extension blocks to be added to a bundle
   at any time during its existence in the DTN.  When a waypoint node
   adds a new extension block to a bundle, that extension block may have
   security services applied to it by that waypoint.  Similarly, a
   waypoint node may add a security service to an existing extension
   block, consistent with its security policy.  For example, a node
   representing a boundary between a trusted part of the network and an



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   untrusted part of the network may wish to apply payload encryption
   for bundles leaving the trusted portion of the network.

   In each case, a node other than the bundle originator may be adding a
   security service to the bundle and, as such, the source for the
   security service will be different than the source of the bundle
   itself.  Security services MUST track their orginating node so as to
   properly apply policy and key selection associated with processing
   the security service at the bundle destination.

   Referring to Figure 1, if the bundle that originates at BN1 is given
   security blocks by BN1, then BN1 is the security-source for those
   blocks as well as being the source of the bundle.  If the bundle that
   originates at BN1 is then given a security block by BN2, then BN2 is
   the security-source for that block even though BN1 remains the bundle
   source.

   A bundle MAY have multiple security blocks and these blocks MAY have
   different security-sources.  Each security block in a bundle will be
   associated with a specific security-operation.  All security blocks
   comprising a security-operation MUST have the same security-source.

   As required in [BPBIS], forwarding nodes MUST transmit blocks in a
   bundle in the same order in which they were received.  This
   requirement applies to all DTN nodes, not just ones that implement
   security processing.  Blocks in a bundle MAY be added or deleted
   according to the applicable specification, but those blocks that are
   both received and transmitted MUST be transmitted in the same order
   that they were received.

2.3.  Mixed Security Policy

   Different nodes in a DTN may have different security-related
   capabilities.  Some nodes may not be security-aware and will not
   understand any security-related extension blocks.  Other nodes may
   have security policies that require evaluation of security services
   at places other than the bundle destination (such as verifying
   integrity signatures at certain waypoint nodes).  Other nodes may
   ignore any security processing if they are not the destination of the
   bundle.  The security services described in this specification must
   allow each of these scenarios.

   Extension blocks representing security services MUST have their block
   processing flags set such that the block (and bundle, where
   applicable) will be treated appropriately by non-security-aware
   nodes.





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   Extension blocks providing integrity services within a bundle MUST
   support options to allow waypoint nodes to evaluate these signatures
   if such nodes have the proper configuraton to do so.

2.4.  User-Selected Ciphersuites

   The security services defined in this specification rely on a a
   variety of ciphersuites providing integrity signatures, ciphertext,
   and other information necessary to populate security blocks.  Users
   may wish to select differing ciphersuites to implement different
   security services.  For example, some users may wish to use a SHA-1
   based hash for integrity whereas other users may require a SHA-2 hash
   instead.  The security services defined in this specification MUST
   provide a mechanism for identifying what ciphersuite has been used to
   populate a security block.

2.5.  Deterministic Processing

   In all cases, the processing order of security services within a
   bundle must avoid ambiguity when evaluating security at the bundle
   destination.  This specification MUST provide determinism in the
   application and evaluation of security services, even when doing so
   results in a loss of flexibility.

3.  Security Block Definitions

   There are three types of security blocks that MAY be included in a
   bundle.  These are the Block Integrity Block (BIB), the Block
   Confidentiality Block (BCB), and the Cryptographic Messaging Syntax
   Block (CMSB).

      The BIB is used to ensure the integrity of its security-target.
      The integrity information in the BIB MAY (when possible) be
      verified by any node in between the BIB security-source and the
      bundle destination.  BIBs MAY be added to, and removed from,
      bundles as a matter of security policy.

      The BCB indicates that the security-target has been encrypted, in
      whole or in part, at the BCB security-source in order to protect
      its content while in transit.  The BCB may be decrypted by
      appropriate nodes in the network, up to and including the bundle
      destination, as a matter of security policy.

      The CMSB contains a Cryptographic Message Syntax (CMS) payload
      used to describe a security service applied to another extension
      block.  NOTE: Applications may choose to simply place CMS text as
      the payload to the bundle.  In such cases, security is considered




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      to be implemented at the application layer and CMSBs are not
      required in that case.

   Certain cipher suites may allow or require multiple instances of a
   block to appear in the bundle.  For example, an integrity cipher
   suite may require two security blocks, one before the payload block
   and one after.  Despite the presence of two security blocks, they
   both comprise the same security-operation - OP(integirty, target) in
   this example.

   A security-operation MUST NOT be applied more than once in a bundle.
   For example, the two security-operations: OP(integrity, payload) and
   OP(integrity, payload) are considered redundant and MUST NOT appear
   together in a bundle.  However, the two security operations
   OP(integrity, payload) and OP(integrity, extension_block_1) MAY both
   be present in the bundle.  Also, the two security operations
   OP(integrity, extension_block_1) and OP(integrity, extension_block_2)
   are unique and may both appear in the same bundle.

   Many of the fields in these block definitions use the Self-Delimiting
   Numeric Value (SDNV) type whose format and encoding is as defined in
   [BPBIS].

3.1.  Block Identification

   This specification requires that every target block of a security
   operation be uniquely identifiable.  The definition of the extension
   block header from [BPBIS] provides such a mechanism in the "block
   number", which provides a unique identifier for a block within a
   bundle.  Within this specification, a target block will be identified
   by its unique block number.

3.2.  Block Representation

   Each security block uses the Canonical Bundle Block Format as defined
   in [BPBIS].  That is, each security block is comprised of the
   following elements:

   o  Block Type Code

   o  Block Number

   o  Block Processing Control Flags

   o  Block Data Length

   o  Block Type Specific Data Fields




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3.2.1.  CMS Block Type-Specific Data Fields

   The contents of the CMS block is a single field of CMS data whose
   length is specified by the BLock Data Length parameter.

3.2.2.  BIB and BCB Block Type-Specific Data Fields

   The structure of the BIB and BCB type-specific data fields are
   identifcal and given in Figure 2.  Although the diagram hints at a
   fixed-format layout, this is purely for the purpose of exposition.
   Except for the "type" field, all fields are variable in length.
   Fields annotated with an '*' are optional, with their inclusion in
   the block indicated by the cipher suite flags field.

   +---------------------------+-------------------------+
   | Security Target (SDNV)    |  Cipher suite ID (SDNV) |
   +---------------------------+-------------------------+
   | Cipher suite Flags (SDNV) | *Source EID (Compound)  |
   +---------------------------+-------------------------+
   |  *Parameters (Compound)   | *Sec. Result (Compound) |
   +---------------------------+-------------------------+


                   Figure 2: BIB and BCB Block Structure

   The BIB and BCB type-specific data fields consist of the following
   fields, some of which are optional.

   o  Security-Target (SDNV) - Uniquely identifies the target of the
      associated security-operation.  This MUST be the block number of a
      block in the bundle.

   o  Cipher suite ID (SDNV) - Identifies the ciphersuite used to
      implement the security service reprsented by this block.

   o  Cipher suite flags (SDNV) - Identifies which optional security
      block fields are present in the block.  The structure of the
      cipher suite flags field is shown in Figure 3.  The presence of an
      optional field is indicated by setting the value of the
      corresponding flag to one.  A value of zero indicates the
      corresponding optional field is not present.  The BPSEC cipher
      suite flags are defined as follows.

      *  bits 6-3 are reserved for future use.

      *  src - bit 2 indicates whether the security source EID is
         present in the block.  This identifief the EID that inserted
         the security service in the bundle.  If the security source is



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         not present then the souce of the block MAY be taken to be the
         bundle source, the previous hop, or some other EID as defined
         by security policy.

      *  parm - bit 1 indicates whether or not the cipher suite
         parameters fields are present in the block.

      *  res - bit 0 indicates whether or not the security result fields
         are present in the block.

                  Bit   Bit   Bit   Bit   Bit   Bit   Bit
                   6     5     4     3     2     1     0
                +-----+-----+-----+-----+-----+-----+-----+
                |    reserved           | src |parm | res |
                +-----+-----+-----+-----+-----+-----+-----+

                       Figure 3: Cipher suite flags

   o  (OPTIONAL) Parameters - compound field of the following two items.

      *  Length (SDNV) - specifies the length of the next field, which
         captures the parameters data.

      *  Data - A byte array encoding one or more cipher suite
         parameters, with each parameter represented as a Type-Length-
         Value (TLV) triplet.  In this triplet, the type and length are
         represented as SDNVs and the value is a byte array holding the
         parmeter.  See Section 3.8 for a list of parameter types that
         MUST be supported by BPSEC implementations.  BPSEC cipher suite
         specifications MAY define their own parameters to be
         represented in this byte array.

   o  (OPTIONAL) Security Result - compound field of the next two items.

      *  Length (SDNV) - specifies the length of the next field, which
         is the security-result data.

      *  Data - A byte array containing the results of the appropriate
         cipher suite specific calculation (e.g., a signature, Message
         Authentication Code (MAC), or cipher-text block key).

3.3.  Block Ordering

   A security-operation may be implemented in a bundle using either one
   or two security blocks.  For example, the operation OP(integrity,
   block) MAY be accomplished by a single BIB block in the bundle, or it
   MAY be accomplished by two BIB blocks in the bundle.  To avoid




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   confusion, we use the following terminology to identify the block or
   blocks comprising a security-operation.

   The terms "First" and "Last" are used ONLY when describing multiple
   security blocks comprising a single security-operation.  A "First"
   block refers to the security block that is closest to the primary
   block in the canonical form of the bundle.  A "Last" block refers to
   the security block that is furthest from the primary block in the
   canonical form of the bundle.

   If a single security block implements the security-operation, then it
   is referred to as a "Lone" block.  For example, when a bundle
   authentication cipher suite requires a single BIB block we refer to
   it as a Lone BAB.  When a bundle authentication cipher suite requires
   two BIB blocks we refer to them as the First BIB and the Last BIB.

   This specification and individual cipher suites impose restrictions
   on what optional fields must and must not appear in First blocks,
   Last blocks, and Lone blocks.

3.4.  Block Integrity Block

   A BIB is an ASB with the following additional restrictions:

      The block-type code value MUST be 0x02.

      The block processing control flags value can be set to whatever
      values are required by local policy.  Cipher suite designers
      should carefully consider the effect of setting flags that either
      discard the block or delete the bundle in the event that this
      block cannot be processed.

      The security-target MUST match the BLock Number of a block within
      the bundle.  The security-target for a BIB MUST NOT reference a
      security block defined in this specification (BIB, BCB, or CMSB).

      The cipher suite ID MUST be documented as an end-to-end
      authentication-cipher suite or as an end-to-end error-detection-
      cipher suite.

      The cipher suite parameters field MAY be present in either a Lone
      BIB or a First BIB.  This field MUST NOT be present in a Last BIB.

      An EID-reference to the security-source MAY be present in either a
      Lone BIB or a First BIB.  This field MUST NOT be present in a Last
      BIB.





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      The security-result captures the result of applying the cipher
      suite calculation (e.g., the MAC or signature) to the relevant
      parts of the security-target, as specified in the cipher suite
      definition.  This field MUST be present in either a Lone BIB or a
      Last BIB.  This field MUST NOT be present in a First BIB.

      The cipher suite MAY process less than the entire security-target.
      If the cipher suite processes less than the complete, original
      security-target, the cipher suite parameters MUST specify which
      bytes of the security-target are protected.

   Notes:

   o  Since OP(integrity, target) is allowed only once in a bundle per
      target, it is RECOMMENDED that users wishing to support multiple
      integrity signatures for the same target define a multi-signature
      cipher suite, capturing multiple security results in cipher suite
      parameters.

   o  For some cipher suites, (e.g., those using asymmetric keying to
      produce signatures or those using symmetric keying with a group
      key), the security information MAY be checked at any hop on the
      way to the destination that has access to the required keying
      information, in accordance with Section 3.7.

   o  The use of a generally available key is RECOMMENDED if custodial
      transfer is employed and all nodes SHOULD verify the bundle before
      accepting custody.

3.5.  Block Confidentiality Block

   A BCB is an ASB with the following additional restrictions:

      The block-type code value MUST be 0x03.

      The block processing control flags value can be set to whatever
      values are required by local policy, except that a Lone BCB or
      First BCB MUST have the "replicate in every fragment" flag set.
      This indicates to a receiving node that the payload portion in
      each fragment represents cipher-text.  This flag SHOULD NOT be set
      otherwise.  Cipher suite designers should carefully consider the
      effect of setting flags that either discard the block or delete
      the bundle in the event that this block cannot be processed.

      The security-target MUST match the BLock Number of a block within
      the bundle.  The security-target for a BCB MAY reference the
      payload block, a non-security extension block, or a BIB block.




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      The cipher suite ID MUST be documented as a confidentiality cipher
      suite.

      Key-information, if available, MUST appear only in a Lone BCB or a
      First BCB.

      Any additional bytes generated as a result of encryption and/or
      authentication processing of the security-target SHOULD be placed
      in an "integrity check value" field (see Section 3.8) in the
      security-result of the Lone BCB or Last BCB.

      The cipher suite parameters field MAY be present in either a Lone
      BCB or a First BCB.  This field MUST NOT be present in a Last BCB.

      An EID-reference to the security-source MAY be present in either a
      Lone BCB or a First BCB.  This field MUST NOT be present in a Last
      BCB.  The security-source can also be specified as part of key-
      information described in Section 3.8.

      The security-result MAY be present in either a Lone BCB or a Last
      BCB.  This field MUST NOT be present in a First BCB.  This
      compound field normally contains fields such as an encrypted
      bundle encryption key and/or authentication tag.

   The BCB is the only security block that modifies the contents of its
   security-target.  When a BCB is applied, the security-target body
   data are encrypted "in-place".  Following encryption, the security-
   target body data contains cipher-text, not plain-text.  Other
   security-target block fields (such as type, processing control flags,
   and length) remain unmodified.

   Fragmentation, reassembly, and custody transfer are adversely
   affected by a change in size of the payload due to ambiguity about
   what byte range of the block is actually in any particular fragment.
   Therefore, when the security-target of a BCB is the bundle payload,
   the BCB MUST NOT alter the size of the payload block body data.
   Cipher suites SHOULD place any block expansion, such as
   authentication tags (integrity check values) and any padding
   generated by a block-mode cipher, into an integrity check value item
   in the security-result field (see Section 3.8) of the BCB.  This "in-
   place" encryption allows fragmentation, reassembly, and custody
   transfer to operate without knowledge of whether or not encryption
   has occurred.

   Notes:

   o  The cipher suite MAY process less than the entire original
      security-target body data.  If the cipher suite processes less



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      than the complete, original security-target body data, the BCB for
      that security-target MUST specify, as part of the cipher suite
      parameters, which bytes of the body data are protected.

   o  The BCB's "discard" flag may be set independently from its
      security-target's "discard" flag.  Whether or not the BCB's
      "discard" flag is set is an implementation/policy decision for the
      encrypting node.  (The "discard" flag is more properly called the
      "Discard if block cannot be processed" flag.)

   o  A BCB MAY include information as part of additional authenticated
      data to address parts of the target block, such as EID references,
      that are not converted to cipher-text.

3.6.  Cryptographic Message Syntax Block

   A CMSB is an ASB with the following additional restrictions:

      The block-type code value MUST be 0x04.

      The content of the block must contain valid CMS data, as defined
      in [RFC5652] , and encoded in X.690 BER or DER encoding.

      The block processing control flags value can be set to whatever
      values are required by local policy.  This flag SHOULD NOT be set
      otherwise.  Cipher suite designers should carefully consider the
      effect of setting flags that either discard the block or delete
      the bundle in the event that this block cannot be processed.

      The security-target MUST uniquely identify a block within the
      bundle.  The reserved block type 0x01 specifies the singleton
      payload block.

      The security operation(s) will be performed on the security-target
      block's data and the resulting CMS content will be stored within
      the CMSB block's security-result field.  The security-target
      block's data will then be removed.

      A CMSB block MAY include multiple CMS security operations within a
      single block to allow for multiple nested operations to be
      performed on a bundle block.  Multiple CMSB blocks MAY be included
      in a bundle as long as the security-target for each is unique.

      Key-information, if available, MUST appear within the CMS content
      contained in the security-result field.

   A CMSB block is created with its corresponding security-target field
   pointing to a unique bundle block.  The CMS security operations are



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   performed upon the security-target's data field and the resulting
   encoded CMS content is stored within the CMS security-result field of
   the CMSB's payload.  The security-target block's data MAY be left
   intact, replaced with alternate data, or completely erased based on
   the specification of the utilized CMS ciphersuite definition and
   applicable policy.

   Multiple CMS operations may be nested within a single CMSB block to
   allow more than one security operation to be performed upon a
   security-target.

   CMS Operations can be considered to have BPSec parallels: CMSB
   Enveloped-Data content type SHALL be considered as equivalent to a
   BPSec BCB block, and a CMSB Signed-Data type SHALL be considered as
   equivalent to a BPSec BIB block.

3.7.  Block Interactions

   The security-block types defined in this specification are designed
   to be as independent as possible.  However, there are some cases
   where security blocks may share a security-target creating processing
   dependencies.

   If confidentiality is being applied to a target that already has
   integrity applied to it, then an undesirable condition occurs where a
   security-aware intermediate node would be unable to check the
   integrity result of a block because the block contents have been
   encrypted after the integrity signature was generated.  To address
   this concern, the following processing rules MUST be followed.

   o  If confidentiality is to be applied to a target, it MUST also be
      applied to every integrity operation already defined for that
      target.  This means that if a BCB is added to encrypt a block,
      another BCB MUST also be added to encrypt a BIB also targeting
      that block.

   o  An integrity operation MUST NOT be applied to a security-target if
      a BCB in the bundle shares the same security-target.  This
      prevents ambiguity in the order of evaluation when receiving a BIB
      and a BCB for a given security-target.

   o  An integrity value MUST NOT be evaluated if the BIB providing the
      integrity value is the security target of an existing BCB block in
      the bundle.  In such a case, the BIB data contains cipher-text as
      it has been encrypted.

   o  An integrity value MUST NOT be evaluated if the security-target of
      the BIB is also the security-target of a BCB in the bundle.  In



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      such a case, the security-target data contains cipher-text as it
      has been encrypted.

   o  As mentioned in Section 3.5, a BIB MUST NOT have a BCB as its
      security target.  BCBs may embed integrity results as part of
      cipher suite parameters.

   o  As mentioned in Section 4.4, CMS operations are considered to have
      operational parallels.  When a CMSB is used, these parallels MUST
      be considered for block interactions (e.g., a Signed-Data
      structure MUST NOT be evaluated if the security-target of the
      operation is also the security-target of a BCB)

   o  If a single bundle is going to contain a CMSB as well as other
      security blocks, the CMS operations MUST be performed and the CMSB
      MUST be created before any other security operation is applied.

   Additionally, since the CMSB block may contain either integrity or
   confidentiality information in its encapsulated CMS, there is no way
   to evaluate conflicts when a BIB/BCB and a CMSB have the same
   security target.  To address this concern, the following processing
   rules MUST be followed.

   o  If an extension block is the target of a BIB or a BCB, then the
      extension block MUST NOT also be the target of a CMSB, and vice-
      versa.

   o  Generally, a CMSB MUST be processed before any BIB or BCB blocks
      are processed.

   These restrictions on block interactions impose a necessary ordering
   when applying security operations within a bundle.  Specifically, for
   a given security-target, BIBs MUST be added before BCBs.  This
   ordering MUST be preserved in cases where the current BPA is adding
   all of the security blocks for the bundle or whether the BPA is a
   waypoint adding new security blocks to a bundle that already contains
   security blocks.

3.8.  Parameters and Result Fields

   Various cipher suites include several items in the cipher suite
   parameters and/or security-result fields.  Which items MAY appear is
   defined by the particular cipher suite description.  A cipher suite
   MAY support several instances of the same type within a single block.

   Each item is represented as a type-length-value.  Type is a single
   byte indicating the item.  Length is the count of data bytes to




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   follow, and is an SDNV-encoded integer.  Value is the data content of
   the item.

   Item types, name, and descriptions are defined as follows.

                Cipher suite parameters and result fields.

   +-------+----------------+------------------------------------------+
   |  Type |      Name      | Description                              |
   +-------+----------------+------------------------------------------+
   |   0   |    Reserved    |                                          |
   +-------+----------------+------------------------------------------+
   |   1   | Initialization | A random value, typically eight to       |
   |       |  Vector (IV)   | sixteen bytes.                           |
   +-------+----------------+------------------------------------------+
   |   2   |    Reserved    |                                          |
   +-------+----------------+------------------------------------------+
   |   3   |      Key       | Material encoded or protected by the key |
   |       |  Information   | management system and used to transport  |
   |       |                | an ephemeral key protected by a long-    |
   |       |                | term key.                                |
   +-------+----------------+------------------------------------------+
   |   4   | Content Range  | Pair of SDNV values (offset,length)      |
   |       |                | specifying the range of payload bytes to |
   |       |                | which an operation applies. The offset   |
   |       |                | MUST be the offset within the original   |
   |       |                | bundle, even if the current bundle is a  |
   |       |                | fragment.                                |
   +-------+----------------+------------------------------------------+
   |   5   |   Integrity    | Result of BAB or BIB digest or other     |
   |       |   Signatures   | signing operation.                       |
   +-------+----------------+------------------------------------------+
   |   6   |   Unassigned   |                                          |
   +-------+----------------+------------------------------------------+
   |   7   |      Salt      | An IV-like value used by certain         |
   |       |                | confidentiality suites.                  |
   +-------+----------------+------------------------------------------+
   |   8   | BCB Integrity  | Output from certain confidentiality      |
   |       |  Check Value   | cipher suite operations to be used at    |
   |       |    (ICV) /     | the destination to verify that the       |
   |       | Authentication | protected data has not been modified.    |
   |       |      Tag       | This value MAY contain padding if        |
   |       |                | required by the cipher suite.            |
   +-------+----------------+------------------------------------------+
   | 9-255 |    Reserved    |                                          |
   +-------+----------------+------------------------------------------+

                                  Table 1



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3.9.  BSP Block Example

   An example of BPSec blocks applied to a bundle is illustrated in
   Figure 4.  In this figure the first column represents blocks within a
   bundle and the second column represents a unique identifier for each
   block, suitable for use as the security-target of a BPSec security-
   block.  Since the mechanism and format of a security-target is not
   specified in this document, the terminology B1...Bn is used to
   identify blocks in the bundle for the purposes of illustration.


            Block in Bundle            ID
   +=================================+====+
   |         Primary Block           | B1 |
   +---------------------------------+----+
   |          Lone BIB               | B2 |
   |  OP(integrity, target=B1)       |    |
   +---------------------------------+----+
   |          Lone BCB               | B3 |
   |  OP(confidentiality, target=B4) |    |
   +---------------------------------+----+
   |      Extension Block            | B4 |
   +---------------------------------+----+
   |          Lone BIB               | B5 |
   |  OP(integrity, target=B6)       |    |
   +---------------------------------+----+
   |      Extension Block            | B6 |
   +---------------------------------+----+
   |          Lone BCB               | B7 |
   |  OP(confidentiality, target=B8) |    |
   +---------------------------------+----+
   |   Lone BIB  (encrypted by B7)   | B8 |
   |  OP(integrity, target=B10)       |    |
   +---------------------------------+----|
   |          Lone BCB               | B9 |
   | OP(confidentiality, target=B10) |    |
   +---------------------------------+----+
   |         Payload Block           |B10 |
   +---------------------------------+----+

                    Figure 4: Sample Use of BSP Blocks

   In this example a bundle has five non-security-related blocks: the
   primary block (B1), three extension blocks (B4,B6,B9), and a payload
   block (B11).  The following security applications are applied to this
   bundle.





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   o  An integrity signature applied to the canonicalized primary block.
      This is accomplished by a single BIB (B2).

   o  Confidentiality for the first extension block (B4).  This is
      accomplished by a single BCB block (B3).

   o  Integrity for the second extension block (B6).  This is
      accomplished by a single BIB block (B5).  NOTE: If the extension
      block B6 contains a representation of the serialized bundle (such
      as a hash over all blocks in the bundle at the time of its last
      transmission) then the BIB block is also providing an
      authentication service from the prior BPSEC-BPA to this BPSEC-BPA.

   o  An integrity signature on the payload (B10).  This is accomplished
      by a single BIB block (B8).

   o  Confidentiality for the payload block and it's integrity
      signature.  This is accomplished by two Lone BCB blocks: B7
      encrypting B8, and B9 encrypting B10.
































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            Block in Bundle                    ID
   +=========================================+====+
   |         Primary Block                   | B1 |
   +-----------------------------------------+----+
   |          First BAB                      | B2 |
   |   OP(authentication, Bundle)            |    |
   +-----------------------------------------+----+
   |          Lone CMSB                      | B3 |
   |     security-target=0x01                |    |
   |     security-result=                    |    |
   |                                         |    |
   |  Signed-Data {                          |    |
   |   Digest Algorithm(s),                  |    |
   |   Enveloped-Data {                      |    |
   |     Encrypted Data,                     |    |
   |     Encrypted Encryption Key(s)         |    |
   |   },                                    |    |
   |   Signature(s) and Certificate Chain(s) |    |
   |  }                                      |    |
   |                                         |    |
   +-----------------------------------------+----+
   |         Payload Block                   | B4 |
   |        (Empty Data Field)               |    |
   +-----------------------------------------+----+
   |          Last BAB                       | B5 |
   |   OP(authentication, Bundle)            |    |
   +-----------------------------------------+----+

                  Figure 5: Sample Bundle With CMS Block

   In this example a bundle has two non-security-related blocks: the
   primary block (B1) and a payload block (B4).  This method would allow
   for the bundle to carry multiple CMS payloads by utilizing a multiple
   CMSB ASBs.  The following security applications are applied to this
   bundle.

   o  Authentication over the bundle.  This is accomplished by two BAB
      blocks: B2 and B5.

   o  Encrypted and signed CMS content contained within the CMSB block.
      The first CMS operation, encryption, is performed on the data
      contained within the block the security-target points to, in this
      case, the payload block.  The resulting encrypted data is then
      signed and the final CMS content is stored within the CMSB block's
      security-result field.  The payload block's data is subsequently
      removed now that the original data has been encoded within the
      CMSB block.




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4.  Security Processing

   This section describes the security aspects of bundle processing.

4.1.  Canonical Forms

   In order to verify a signature of a block, the exact same bits, in
   the exact same order, MUST be input to the calculation upon
   verification as were input upon initial computation of the original
   signature value.

   Many fields in various blocks are stored as variable-length SDNVs.
   These are canonicalized into an "unpacked form" as eight-byte fixed-
   width fields in network byte order.

4.1.1.  Block Canonicalization

   This algorithm protects those parts of a block that SHOULD NOT be
   changed in transit.

   There are three types of blocks that may undergo block
   canonicalization: the primary block, the payload block, or an
   extension block.

4.1.1.1.  Primary Block Canonicalization

   The canonical form of the primary block is shown in Figure 6.
   Essentially, it de-references the dictionary block, adjusts lengths
   where necessary, and ignores flags that may change in transit.






















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   +----------------+----------------+----------------+----------------+
   |    Version     |      Processing flags (incl. COS and  SRR)       |
   +----------------+----------------+---------------------------------+
   |                Canonical primary block length                     |
   +----------------+----------------+---------------------------------+
   |                Destination endpoint ID length                     |
   +----------------+----------------+---------------------------------+
   |                      Destination endpoint ID                      |
   +----------------+----------------+---------------------------------+
   |                    Source endpoint ID length                      |
   +----------------+----------------+----------------+----------------+
   |                        Source endpoint ID                         |
   +----------------+----------------+---------------------------------+
   |                  Report-to endpoint ID length                     |
   +----------------+----------------+----------------+----------------+
   |                      Report-to endpoint ID                        |
   +----------------+----------------+----------------+----------------+
   +                    Creation Timestamp (2 x SDNV)                  +
   +---------------------------------+---------------------------------+
   |                             Lifetime                              |
   +----------------+----------------+----------------+----------------+

         Figure 6: The Canonical Form of the Primary Bundle Block

   The fields shown in Figure 6 are as follows:

   o  The version value is the single-byte value in the primary block.

   o  The processing flags value in the primary block is an SDNV, and
      includes the class-of-service (COS) and status report request
      (SRR) fields.  For purposes of canonicalization, the unpacked SDNV
      is ANDed with mask 0x0000 0000 0007 C1BE to set to zero all
      reserved bits and the "bundle is a fragment" bit.

   o  The canonical primary block length value is a four-byte value
      containing the length (in bytes) of this structure, in network
      byte order.

   o  The destination endpoint ID length and value are the length (as a
      four-byte value in network byte order) and value of the
      destination endpoint ID from the primary bundle block.  The URI is
      simply copied from the relevant part(s) of the dictionary block
      and is not itself canonicalized.  Although the dictionary entries
      contain "null-terminators", the null-terminators are not included
      in the length or the canonicalization.

   o  The source endpoint ID length and value are handled similarly to
      the destination.



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   o  The report-to endpoint ID length and value are handled similarly
      to the destination.

   o  The unpacked SDNVs for the creation timestamp and lifetime are
      copied from the primary block.

   o  Fragment offset and total application data unit length are
      ignored, as is the case for the "bundle is a fragment" bit
      mentioned above.  If the payload data to be canonicalized is less
      than the complete, original bundle payload, the offset and length
      are specified in the cipher suite parameters.

4.1.1.2.  Payload Block Canonicalization

   When canonicalizing the payload block, the block processing control
   flags value used for canonicalization is the unpacked SDNV value with
   reserved and mutable bits masked to zero.  The unpacked value is
   ANDed with mask 0x0000 0000 0000 0077 to zero reserved bits and the
   "last block" bit.  The "last block" bit is ignored because BABs and
   other security blocks MAY be added for some parts of the journey but
   not others, so the setting of this bit might change from hop to hop.

   Payload blocks are canonicalized as-is, with the exception that, in
   some instances, only a portion of the payload data is to be
   protected.  In such a case, only those bytes are included in the
   canonical form, and additional cipher suite parameters are required
   to specify which part of the payload is protected, as discussed
   further below.

4.1.1.3.  Extension Block Canonicalization

   When canonicalizing an extension block, the block processing control
   flags value used for canonicalization is the unpacked SDNV value with
   reserved and mutable bits masked to zero.  The unpacked value is
   ANDed with mask 0x0000 0000 0000 0057 to zero reserved bits, the
   "last block" flag and the "Block was forwarded without being
   processed" bit.  The "last block" flag is ignored because BABs and
   other security blocks MAY be added for some parts of the journey but
   not others, so the setting of this bit might change from hop to hop.

   The "Block was forwarded without being processed" flag is ignored
   because the bundle may pass through nodes that do not understand that
   extension block and this flag would be set.

   Endpoint ID references in blocks are canonicalized using the de-
   referenced text form in place of the reference pair.  The reference
   count is not included, nor is the length of the endpoint ID text.




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   The EID reference is, therefore, canonicalized as <scheme>:<SSP>,
   which includes the ":" character.

   Since neither the length of the canonicalized EID text nor a null-
   terminator is used in EID canonicalization, a separator token MUST be
   used to determine when one EID ends and another begins.  When
   multiple EIDs are canonicalized together, the character "," SHALL be
   placed between adjacent instances of EID text.

   The block-length is canonicalized as its unpacked SDNV value.  If the
   data to be canonicalized is less than the complete, original block
   data, this field contains the size of the data being canonicalized
   (the "effective block") rather than the actual size of the block.

4.1.2.  Considerations

   o  The canonical forms for the bundle and various extension blocks is
      not transmitted.  It is simply an artifact used as input to
      digesting.

   o  We omit the reserved flags because we cannot determine if they
      will change in transit.  The masks specified above will have to be
      revised if additional flags are defined and they need to be
      protected.

   o  All SDNV fields here are canonicalized as eight-byte unpacked
      values in network byte order.  Length fields are canonicalized as
      four-byte values in network byte order.  Encoding does not need
      optimization since the values are never sent over the network.

   o  These canonicalization algorithms assume that endpoint IDs
      themselves are immutable and they are unsuitable for use in
      environments where that assumption might be violated.

   o  Cipher suites MAY define their own canonicalization algorithms and
      require the use of those algorithms over the ones provided in this
      specification.

4.2.  Endpoint ID Confidentiality

   Every bundle has a primary block that contains the source and
   destination endpoint IDs, and possibly other EIDs (in the dictionary
   field) that cannot be encrypted.  If endpoint ID confidentiality is
   required, then bundle-in-bundle encapsulation can solve this problem
   in some instances.






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   Similarly, confidentiality requirements MAY also apply to other parts
   of the primary block (e.g., the current-custodian), and that is
   supported in the same manner.

4.3.  Bundles Received from Other Nodes

   Security blocks MUST be processed in a specific order when received
   by a security-aware node.  The processing order is as follows.

   o  All BCB blocks in the bundle MUST be evaluated prior to evaluating
      any BIBs in the bundle.  When BIBs and BCBs share a security-
      target, BCBs MUST be evaluated first and BIBs second.

4.3.1.  Receiving BCB Blocks

   If the bundle has a BCB and the receiving node is the destination for
   the bundle, the node MUST decrypt the relevant parts of the security-
   target in accordance with the cipher suite specification.

   If the relevant parts of an encrypted payload cannot be decrypted
   (i.e., the decryption key cannot be deduced or decryption fails),
   then the bundle MUST be discarded and processed no further; in this
   case, a bundle deletion status report (see [BPBIS]) indicating the
   decryption failure MAY be generated.  If any other encrypted
   security-target cannot be decrypted then the associated security-
   target and all security blocks associated with that target MUST be
   discarded and processed no further.

   When a BCB is decrypted, the recovered plain-text MUST replace the
   cipher-text in the security-target body data

4.3.2.  Receiving BIB Blocks

   A BIB MUST NOT be processed if the security-target of the BIB is also
   the security-target of a BCB in the bundle.  Given the order of
   operations mandated by this specification, when both a BIB and a BCB
   share a security-target, it means that the security-target MUST have
   been encrypted after it was integrity signed and, therefore, the BIB
   cannot be verified until the security-target has been decrypted by
   processing the BCB.

   If the security policy of a security-aware node specifies that a
   bundle SHOULD apply integrity to a specific security-target and no
   such BIB is present in the bundle, then the node MUST process this
   security-target in accordance with the security policy.  This MAY
   involve removing the security-target from the bundle.  If the removed
   security-target is the payload or primary block, the bundle MAY be




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   discarded.  This action may occur at any node that has the ability to
   verify an integrity signature, not just the bundle destination.

   If the bundle has a BIB and the receiving node is the destination for
   the bundle, the node MUST verify the security-target in accordance
   with the cipher suite specification.  If a BIB check fails, the
   security-target has failed to authenticate and the security-target
   SHALL be processed according to the security policy.  A bundle status
   report indicating the failure MAY be generated.  Otherwise, if the
   BIB verifies, the security-target is ready to be processed for
   delivery.

   If the bundle has a BIB and the receiving node is not the bundle
   destination, the receiving node MAY attempt to verify the value in
   the security-result field.  If the check fails, the node SHALL
   process the security-target in accordance to local security policy.
   It is RECOMMENDED that if a payload integrity check fails at a
   waypoint that it is processed in the same way as if the check fails
   at the destination.

4.4.  Receiving CMSB Blocks

   A CMSB MUST NOT be processed if its security target is also the
   security target of any BIB or BCB in the bundle.

   The security services provided by a CMSB will be considered
   successful if all services in the CMSB are validated.  If any one
   service encapsulated in the CMSB fails to validate, then the CMSB
   MUST be considered as having failed to validate and MUST be
   dispositioned in accordance with security policy.

4.5.  Bundle Fragmentation and Reassembly

   If it is necessary for a node to fragment a bundle and security
   services have been applied to that bundle, the fragmentation rules
   described in [BPBIS] MUST be followed.  As defined there and repeated
   here for completeness, only the payload may be fragmented; security
   blocks, like all extension blocks, can never be fragmented.  In
   addition, the following security-specific processing is REQUIRED:

   o  Due to the complexity of bundle fragmentation, including the
      possibility of fragmenting bundle fragments, integrity and
      confidentiality operations are not to be applied to a bundle
      fragment.  Specifically, a BCB or BIB MUST NOT be added to a
      bundle fragment, even if the security-target of the security block
      is not the payload.  When integrity and confidentiality must be
      applied to a fragment, we RECOMMEND that encapsulation be used
      instead.



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   o  The authentication security policy requirements for a bundle MUST
      be applied individually to all the bundles resulting from a
      fragmentation event.

   o  The decision to fragment a bundle MUST be made prior to adding
      authentication to the bundle.  The bundle MUST first be fragmented
      and authentication applied to each individual fragment.

4.6.  Reactive Fragmentation

   When a partial bundle has been received, the receiving node SHALL
   consult its security policy to determine if it MAY fragment the
   bundle, converting the received portion into a bundle fragment for
   further forwarding.  Whether or not reactive fragmentation is
   permitted SHALL depend on the security policy and the cipher suite
   used to calculate the BAB authentication information, if required.

   Specifically, if the security policy does not require authentication,
   then reactive fragmentation MAY be permitted.  If the security policy
   does require authentication, then reactive fragmentation MUST NOT be
   permitted if the partial bundle is not sufficient to allow
   authentication.

   If reactive fragmentation is allowed, then all BAB blocks must be
   removed from created fragments.

5.  Key Management

   Key management in delay-tolerant networks is recognized as a
   difficult topic and is one that this specification does not attempt
   to solve.

6.  Policy Considerations

   When implementing BPSec, several policy decisions must be considered.
   This section describes key policies that affect the generation,
   forwarding, and receipt of bundles that are secured using this
   specification.

   o  If a bundle is received that contains more than one security-
      operation, in violation of BPSec, then the BPA must determine how
      to handle this bundle.  The bundle may be discarded, the block
      affected by the security-operation may be discarded, or one
      security-operation may be favored over another.

   o  BPAs in the network MUST understand what security-operations they
      should apply to bundles.  This decision may be based on the source




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      of the bundle, the destination of the bundle, or some other
      information related to the bundle.

   o  If an intermediate receiver has been configured to add a security-
      operation to a bundle, and the received bundle already has the
      security-operation applied, then the receiver MUST understand what
      to do.  The receiver may discard the bundle, discard the security-
      target and associated BPSec blocks, replace the security-
      operation, or some other action.

   o  It is recommended that security operations only be applied to the
      payload block, the primary block, and any block-types specifically
      identified in the security policy.  If a BPA were to apply
      security operations such as integrity or confidentiality to every
      block in the bundle, regardless of the block type, there could be
      downstream errors processing blocks whose contents must be
      inspected at every hop in the network path.

7.  Security Considerations

   Certain applications of DTN need to both sign and encrypt a message,
   and there are security issues to consider with this.

   o  To provide an assurance that a security-target came from a
      specific source and has not been changed, then it should be signed
      with a BIB.

   o  To ensure that a security-target cannot be inspected during
      transit, it should be encrypted with a BCB.

   o  Adding a BIB to a security-target that has already been encrypted
      by a BCB is not allowed.  Therefore, we recommend three methods to
      add an integrity signature to an encrypted security-target.
      First, at the time of encryption, an integrity signature may be
      generated and added to the BCB for the security-target as
      additional information in the security-result field.  Second, the
      encrypted block may be replicated as a new block and integrity
      signed.  Third, an encapsulation scheme may be applied to
      encapsulate the security-target (or the entire bundle) such that
      the encapsulating structure is, itself, no longer the security-
      target of a BCB and may therefore be the security-target of a BIB.

8.  Conformance

   All implementations are strongly RECOMMENDED to provide some method
   of hop-by-hop verification by generating a hash to some canonical
   form of the bundle and placing an integrity signature on that form
   using a BIB.



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9.  IANA Considerations

   This protocol has fields that have been registered by IANA.

9.1.  Bundle Block Types

   This specification allocates three block types from the existing
   "Bundle Block Types" registry defined in [RFC6255] .

       Additional Entries for the Bundle Block-Type Codes Registry:

          +-------+-----------------------------+---------------+
          | Value |         Description         |   Reference   |
          +-------+-----------------------------+---------------+
          |   2   |    Block Integrity Block    | This document |
          |   3   | Block Confidentiality Block | This document |
          |   4   |          CMS Block          | This document |
          +-------+-----------------------------+---------------+

                                  Table 2

9.2.  Cipher Suite Flags

   This protocol has a cipher suite flags field and certain flags are
   defined.  An IANA registry has been set up as follows.

   The registration policy for this registry is: Specification Required

   The Value range is: Variable Length

                        Cipher Suite Flag Registry:

   +--------------------------+-------------------------+--------------+
   |  Bit Position (right to  |       Description       |  Reference   |
   |          left)           |                         |              |
   +--------------------------+-------------------------+--------------+
   |            0             |  Block contains result  |     This     |
   |                          |                         |   document   |
   |            1             |      Block Contains     |     This     |
   |                          |        parameters       |   document   |
   |            2             |  Source EID ref present |     This     |
   |                          |                         |   document   |
   |            >3            |         Reserved        |     This     |
   |                          |                         |   document   |
   +--------------------------+-------------------------+--------------+

                                  Table 3




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9.3.  Parameters and Results

   This protocol has fields for cipher suite parameters and results.
   The field is a type-length-value triple and a registry is required
   for the "type" sub-field.  The values for "type" apply to both the
   cipher suite parameters and the cipher suite results fields.  Certain
   values are defined.  An IANA registry has been set up as follows.

   The registration policy for this registry is: Specification Required

   The Value range is: 8-bit unsigned integer.

            Cipher Suite Parameters and Results Type Registry:

       +---------+---------------------------------+---------------+
       |  Value  |           Description           |   Reference   |
       +---------+---------------------------------+---------------+
       |    0    |             reserved            | This document |
       |    1    |    initialization vector (IV)   | This document |
       |    2    |             reserved            | This document |
       |    3    |         key-information         | This document |
       |    4    |  content-range (pair of SDNVs)  | This document |
       |    5    |       integrity signature       | This document |
       |    6    |            unassigned           | This document |
       |    7    |               salt              | This document |
       |    8    | BCB integrity check value (ICV) | This document |
       |  9-191  |             reserved            | This document |
       | 192-250 |           private use           | This document |
       | 251-255 |             reserved            | This document |
       +---------+---------------------------------+---------------+

                                  Table 4

10.  References

10.1.  Normative References

   [BPBIS]    Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol",
              draft-ietf-dtn-bpbis-03 (work in progress), March 2016.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <http://www.rfc-editor.org/info/rfc5652>.





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   [RFC6255]  Blanchet, M., "Delay-Tolerant Networking Bundle Protocol
              IANA Registries", RFC 6255, May 2011.

10.2.  Informative References

   [RFC4838]  Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
              R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant
              Networking Architecture", RFC 4838, April 2007.

   [RFC6257]  Symington, S., Farrell, S., Weiss, H., and P. Lovell,
              "Bundle Security Protocol Specification", RFC 6257, May
              2011.

   [SBSP]     Birrane, E., "Streamlined Bundle Security Protocol",
              draft-birrane-dtn-sbsp-01 (work in progress), October
              2015.

Appendix A.  Acknowledgements

   The following participants contributed technical material, use cases,
   and useful thoughts on the overall approach to this security
   specification: Scott Burleigh of the Jet Propulsion Laboratory, Amy
   Alford and Angela Hennessy of the Laboratory for Telecommunications
   Sciences, and Angela Dalton and Cherita Corbett of the Johns Hopkins
   University Applied Physics Laboratory.

Authors' Addresses

   Edward J. Birrane, III
   The Johns Hopkins University Applied Physics Laboratory
   11100 Johns Hopkins Rd.
   Laurel, MD  20723
   US

   Phone: +1 443 778 7423
   Email: Edward.Birrane@jhuapl.edu


   Jeremy Pierce-Mayer
   INSYEN AG
   Muenchner Str. 20
   Oberpfaffenhofen, Bavaria  DE
   Germany

   Phone: +49 08153 28 2774
   Email: jeremy.mayer@insyen.com





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   Dennis C. Iannicca
   NASA Glenn Research Center
   21000 Brookpark Rd.
   Brook Park, OH  44135
   US

   Phone: +1-216-433-6493
   Email: dennis.c.iannicca@nasa.gov











































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