Network Working Group P. Hallam-Baker
Internet-Draft Comodo Group Inc.
Intended status: Informational August 16, 2017
Expires: February 17, 2018
Mesh/Recrypt: Usable Confidentiality
draft-hallambaker-mesh-recrypt-02
Abstract
independent
A messaging infrastructure providing full end-to end security is
presented. Unlike existing approaches such as S/MIME and OpenPGP,
Mesh/Recrypt uses proxy re-encryption to preserve full end-to-end
security with individual user and device keys in situations such as
the user having multiple decryption devices and messages being set to
mailing lists.
This document shows the use of Mesh/Recrypt to address the principle
use cases Mesh/Recrypt is designed to address. These include
asynchronous messaging such as mail and controlled documents and
synchronous messaging applications such as chat, voice and video.
This document is also available online at
http://prismproof.org/Documents/draft-hallambaker-mesh-recrypt.html .
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
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."
This Internet-Draft will expire on February 17, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Related Specifications . . . . . . . . . . . . . . . . . 5
2.2. Defined Terms . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Requirements Language . . . . . . . . . . . . . . . . . . 5
3. Proxy Re-Encryption . . . . . . . . . . . . . . . . . . . . . 5
3.1. Proxy Re-Encryption Algorithms . . . . . . . . . . . . . 6
3.2. Applying Mesh/Recrypt . . . . . . . . . . . . . . . . . . 10
3.3. Mailing Lists . . . . . . . . . . . . . . . . . . . . . . 10
3.4. Chat rooms and other streaming data. . . . . . . . . . . 10
3.5. Confidential Document Control . . . . . . . . . . . . . . 11
3.6. Multiple Devices . . . . . . . . . . . . . . . . . . . . 12
4. Mesh/Recrypt/Admin Service . . . . . . . . . . . . . . . . . 12
4.1. Request Messages . . . . . . . . . . . . . . . . . . . . 13
4.1.1. Message: RecryptRequest . . . . . . . . . . . . . . . 13
4.2. Response Messages . . . . . . . . . . . . . . . . . . . . 13
4.2.1. Message: RecryptResponse . . . . . . . . . . . . . . 13
4.3. Imported Objects . . . . . . . . . . . . . . . . . . . . 13
4.4. Common classes . . . . . . . . . . . . . . . . . . . . . 13
4.4.1. Structure: RecryptionGroup . . . . . . . . . . . . . 13
4.4.2. Structure: MemberEntry . . . . . . . . . . . . . . . 14
4.4.3. Structure: UserDecryptionEntry . . . . . . . . . . . 15
4.4.4. Structure: CombinedToGroup . . . . . . . . . . . . . 15
4.5. Administrator Transactions . . . . . . . . . . . . . . . 16
4.6. Transaction: Hello . . . . . . . . . . . . . . . . . . . 16
4.7. Transaction: CreateGroup . . . . . . . . . . . . . . . . 16
4.7.1. Message: CreateGroupRequest . . . . . . . . . . . . . 16
4.7.2. Message: CreateGroupResponse . . . . . . . . . . . . 17
4.8. Transaction: UpdateGroup . . . . . . . . . . . . . . . . 17
4.8.1. Message: UpdateGroupRequest . . . . . . . . . . . . . 17
4.8.2. Message: UpdateGroupResponse . . . . . . . . . . . . 17
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4.9. Transaction: AddMember . . . . . . . . . . . . . . . . . 17
4.9.1. Message: AddMemberRequest . . . . . . . . . . . . . . 18
4.9.2. Message: AddMemberResponse . . . . . . . . . . . . . 18
4.10. Transaction: UpdateMember . . . . . . . . . . . . . . . . 18
4.10.1. Message: UpdateMemberRequest . . . . . . . . . . . . 18
4.10.2. Message: UpdateMemberResponse . . . . . . . . . . . 19
4.11. Future work . . . . . . . . . . . . . . . . . . . . . . . 19
5. User Service . . . . . . . . . . . . . . . . . . . . . . . . 19
5.1. Transaction: RecryptData . . . . . . . . . . . . . . . . 19
5.1.1. Message: RecryptDataRequest . . . . . . . . . . . . . 19
5.1.2. Message: RecryptDataResponse . . . . . . . . . . . . 20
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 20
7.1. Reference Implementation . . . . . . . . . . . . . . . . 20
7.1.1. Coverage: . . . . . . . . . . . . . . . . . . . . . . 21
7.1.2. Licensing . . . . . . . . . . . . . . . . . . . . . . 21
7.1.3. Implementation Experience . . . . . . . . . . . . . . 21
7.1.4. Contact Info . . . . . . . . . . . . . . . . . . . . 21
8. Security Considerations . . . . . . . . . . . . . . . . . . . 22
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
10.1. Normative References . . . . . . . . . . . . . . . . . . 22
10.2. Informative References . . . . . . . . . . . . . . . . . 22
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction
Traditional messaging security infrastructures are difficult to
configure, difficult to use and limited to one mode of communication.
Digital certificates are hard to obtain and harder to maintain.
Managing a Web of Trust requires a very high level of user
competence. S/MIME and OpenPGP offer end-to-end email security but
not streaming services such as video, voice or chat.
In recent years a number of proprietary chat systems have been
extended to the point that a single application and protocol supports
chat, voice, video and asynchronous communication modes such as
messaging and file transfer. While such systems typically claim to
offer cryptographic security, the extent to which this is achieved is
difficult to determine. Even systems purporting to offer ?end-to-
end? security have proved to be woefully inadequate when it is
discovered that one of the ?ends? referred to is in fact the
messaging infrastructure operated by the provider.
A key limitation of all the deployed messaging systems that were
reviewed in the development of this paper is that true end-to-end
confidentiality is only achieved for a limited set of communication
patterns. Specifically, bilateral communications (Alice sends a
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message to Bob) or broadcast communications to a known set of
recipients (Alice sends a message to Bob, Carol and Doug). These
capabilities do not support communication patterns where the set of
recipients changes over time or is confidential. Yet such
requirements commonly occur in situations such as sending a message
to a mailing list whose membership isn?t known to the sender, or
creating a spreadsheet whose readership is to be limited to
authorized members of the ?accounting? team.
[[This figure is not viewable in this format. The figure is
available at http://prismproof.org/Documents/draft-hallambaker-mesh-
recrypt.html.]]
Traditional End-to-End Encryption is static.
Mesh/Recrypt is an experimental messaging infrastructure that applies
proxy re-encryption to support all the commonly used messaging modes
with strong end-to-end encryption. The primary purpose of Mesh/
Recrypt is to demonstrate the advantages of using the proxy re-
encryption technique and to determine the feasibility of retrofitting
such capabilities to legacy protocols such as SMTP, IMAP and XMPP.
[[This figure is not viewable in this format. The figure is
available at http://prismproof.org/Documents/draft-hallambaker-mesh-
recrypt.html.]]
Mesh Recrypt supports End-to-End Encryption in dynamic groups.
Whether the advantages of building on an established base outweigh
those of a clean slate approach for purposes of deployment are
currently unknown, but there are clear advantages of using a clean
slate approach for purposes of exposition.
As the name suggests, Mesh/Recrypt makes use of the Mathematical Mesh
infrastructure for management of user keys. For clarity and
convenience, this document describes the application of Mesh/Recrypt
to a completely new protocol suite. Strategies for adding similar
capabilities to existing specifications are discussed as possible
future work.
2. Definitions
This section presents the related specifications and standards on
which Mesh/Recrypt is built, the terms that are used as terms of art
within the documents and the terms used as requirements language.
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2.1. Related Specifications
The related specifications used in the Mesh/Recrypt protocol are
described in the Mesh Architecture specification [draft-hallambaker-
mesh-architecture] [draft-hallambaker-mesh-architecture]
2.2. Defined Terms
The following terms are used as terms of art in this document with
the meaning specified below:
An Access Control mechanism that uses cryptography to control read
access to static content (typically documents) within its control.
Content that is subject to control of a CDC system.
A cryptography mechanism that permits a party that does not have
the ability to decrypt an encrypted message to transform it into a
message that can be decrypted under a different private key than
the original.
The term ?recryption? is used as a synonym for Proxy Re-Encryption
in this document.
A cryptographic key that is used to enable a different party to
decrypt an encrypted message that does not grant decryption
capability.
2.3. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119] [RFC2119] .
3. Proxy Re-Encryption
Proxy re-encryption provides a technical capability that meets the
needs of such communication patterns. Conventional symmetric key
cryptography uses a single key to encrypt and decrypt data. Public
key cryptography uses two keys, the key used to encrypt data is
separate from the key used to decrypt. Proxy re-encryption
introduces a third key (the recryption key) that allows a party to
permit an encrypted data packet to be decrypted using a different key
without permitting the data to be decrypted.
The introduction of a recryption key permits end-to-end
confidentiality to be preserved when a communication pattern requires
that some part of the communication be supported by a service.
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The introduction of a third type of key, the recryption key permits
two new roles to be established, that of an administrator and
recryption service. There are thus four parties:
Holder of Decryption Key, Creator of Recryption Keys
Holder of Encryption Key
Holder of Recryption keys
Holder of personal decryption key
The communication between these parties is shown in Figure X below:
[[This figure is not viewable in this format. The figure is
available at http://prismproof.org/Documents/draft-hallambaker-mesh-
recrypt.html.]]
Mesh/Recrypt Parties
The chief advantage of recryption is that the recryption service does
not have the ability to decrypt messages and does not need to be
trusted at the same level as a recipient. A recryption service may
be implemented as a cloud service on an untrusted host or managed in
house by a system administrator who is only partially trusted.
3.1. Proxy Re-Encryption Algorithms
Proxy Re-Encryption was introduced by Blaze et. al. [Blaze98]
[Blaze98] in 1998. In this paper, we make use of the Diffie Hellman
based mechanism described in this paper. While this approach does
not have capabilities such as reversibility or transitivity offered
in later work, such features do not appear to offer any practical
advantages in developing protocols for the intended applications and
may well introduce significant disadvantages.
The use of the Diffie Hellman based approach has the considerable
advantages of being compatible with the recently developed CFRG
Elliptic Curve algorithms and being minimally unencumbered by IPR
claims.
Recall that in the Diffie Hellman key agreement algorithm, shared
parameters e and p are generated, these being an exponent value (e)
and a modulus value (p). To create a shared key, two parties (Alice
and Bob) generate private keys a, b being positive integers in the
interval [2 ... p-1]. The corresponding public keys are then ea mod
p and eb mod p. Thus, knowledge of either {eb mod p, a} or {ea mod
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p, b} is sufficient to calculate the shared secret value s = eab mod
p.
[[This figure is not viewable in this format. The figure is
available at http://prismproof.org/Documents/draft-hallambaker-mesh-
recrypt.html.]]
Traditional Diffie-Hellman
When applying Diffie Hellman to a messaging protocol, it is typically
desirable to ensure that a unique shared value is created for each
exchange. If the protocol only requires authentication of the
receiver, the sender may ensure that each shared value is unique by
generating a new key pair {t, et mod p} for each exchange.
Alternatively, mutual authentication may be preserved if the shared
secret is formed from three values s = eabt mod p, where a and b are
the validated public keys of the sender and receiver and t is a
temporary key generated by the sender that has a nonce-like function.
To adapt Diffie Hellman to a recryption mechanism, we note that just
as the value s = ebt mod p may be calculated as either (eb mod p)t
mod p or (et mod p)b mod p, it can also be calculated as ((et mod
p)b-x mod p . (et mod p)x mod p) mod p. This equivalence is used to
create the recryption protocol.
Figure XX shows Bob calculating the shared secret with the aid of a
Recryption service. Bob's private key for decryption is now x and
the Recryption service has the corresponding recryption key b-x. The
recryption service can provide Bob with the additional information
needed to decrypt the message but cannot decrypt the message itself.
[[This figure is not viewable in this format. The figure is
available at http://prismproof.org/Documents/draft-hallambaker-mesh-
recrypt.html.]]
Diffie-Hellman with Recryption
Applying this approach to Proxy Re-Encryption directly is
unacceptable since the administrator of the recryption group must
know Bob's private key. To avoid this problem, the administrator
generates a new public key pair for each member of the group and
encrypts the decryption portion under the public key of the member.
In the following example, Alice is the administrator of the
recryption group and Bob and Carol are recipients.
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Generates a public key encryption pair (b, B). The algorithm used
for this does not matter, as the only functions used are
encryption and decryption.
Bob publishes his public key B.
Generates public key pair {a, ea mod p}.
Publishes the public key value for the recryption group ea mod p
To enable Bob to receive messages, Alice generates a recryption
keypair for Bob {a-bx, bx } and encrypts the decryption key (bx)
using Bob?s public key (pubB) to create a recryption entry for Bob
{a- bx, E(bx, pubB)}.
The recryption entry is sent to the recryption service.
At this point Alice, Bob and the Recryption Service have the
information they need to receive encrypted messages (figure X).
[[This figure is not viewable in this format. The figure is
available at http://prismproof.org/Documents/draft-hallambaker-mesh-
recrypt.html.]]
Mesh/Recrypt Administration Protocol
Having established the necessary keying material, Carol (or any other
party who knows the recryption group encryption key) can encrypt a
message:
Generates a temporary key pair {t, et mod p} and uses this and the
public key of the recryption group (ea mod p) to create a shared
secret s = eat mod p that is used to encrypt the message.
Sends the encrypted message and temporary public key (et mod p) to
the recryption service
Receives the message and retrieves the list of intended
recipients, this currently has just a single entry for Bob {a-bx,
E(bx, B)}
Calculates (et mod p)a-bx mod p = eta-tbx mod p
Sends the encrypted message, the original temporary public key
generated by Carol (et mod p), the recryption value eta-tbx mod p
and the encrypted decryption key E(bx, B) to Bob.
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Receives the message
Decrypts the E(bx, B) using his private key b to obtain bx
Uses bx and et mod p to calculate etbx mod p
Calculates (eta-tbx mod p. etbx mod p) mod p = eta mod p = s
Uses s to decrypt the message
This protocol is illustrated in figure X:
[[This figure is not viewable in this format. The figure is
available at http://prismproof.org/Documents/draft-hallambaker-mesh-
recrypt.html.]]
Mesh/Recrypt Decryption Protocol
Note that Alice is not a participant in the recryption protocol.
Administrator actions are only required when adding or removing
recipients to the recryption group.
Alice can add additional recipients to the group at any time by
creating a recryption pair, encrypting the decryption key under the
new user's public key and sending the information to the recryption
service, just like she did for Bob.
Alice can remove a user from the recryption group by telling the
recryption service to no longer recrypt messages to the removed
user?s recryption key. This requires the recryption service to be
trusted not to forward messages to the deleted user. To restore the
untrusted status of the recryption service it is necessary for the
administrator to create a new encryption key and a full set of
recryption keys for the continuing users.
One major limitation in the trust model of the recryption scheme
described is that while it is not possible for either the recryption
service or individual recipients to decrypt arbitrary messages the
recryption service and a recipient may do so if they collude. This
particular limitation in the trust model is an inescapable
consequence of the fact that the function of the recryption service
is to enable a recipient to decrypt a message and cannot be avoided
without introducing additional parties. This limitation is not
considered to be a serious limitation for the intended application.
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3.2. Applying Mesh/Recrypt
This document describes the Mesh/Recrypt algorithm and protocol. To
make use of the capability it provides, it is necessary to make use
of it in an application protocol. Mesh/Recrypt MAY be used in any
application that supports data level encryption. This includes
mailing lists, conferencing systems offering voice or chat and
confidential document control.
3.3. Mailing Lists
One of the earliest uses proposed for recryption is to support end-
to-end security for a confidential mailing list in which the
membership of the list is not disclosed to its members. In this
application, the mail server is a recryption service and trusted to
maintain the confidentiality of the mailing list membership but not
the messages themselves. This offers many advantages over existing
approaches:
o Messages are encrypted end-to-end
o It is not necessary for senders to know the membership of the
list.
o New members added to the list can read messages sent before they
joined.
To apply recryption to a mailing list server, a recryption keyset is
created for each mailing list managed by the server and the
administrator responsible for maintaining the membership of the list
is also the administrator of the corresponding recryption key set.
3.4. Chat rooms and other streaming data.
The application of recryption to a chat room application is similar
to the mailing list application except that the administrator may be
either an offline party as before or a participant in the
conversation. In the latter case, the protocol should permit the
administrator to pass their role to another participant should they
need to leave.
One major constraint on the use of recryption to support streamed
audio or video is that since the messaging service cannot decrypt the
data stream, it can hardly be expected to perform transcoding
services such as producing lower resolution versions of a video
stream to support participants with low bandwidth connections.
Either all the participants must receive the exact same data feed or
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transcoding services must be provided by a trusted party granted
access by the administrator.
3.5. Confidential Document Control
Confidential Document Control (CDC) uses cryptography to enforce
access control. Unlike Digital Rights Management and related
technologies, CDC only provides a means to permit or deny access to
confidential data while it is under protection. A CDC infrastructure
does not attempt to control the use made of that data by an
authorized recipient, in particular, a CDC infrastructure does not
necessarily prevent redistribution of data by a party permitted to
read it.
The application of recryption to CDC maps naturally to the use of
?security labels? to control access to confidential documents in
government and military applications. Each security label (e.g.
secret#example.com) has an associated recryption key set. The
administrator of the recryption key set is responsible for managing
the parties authorized to read documents controlled under that label.
Recryption may be used to support the use of multiple labels.
Combining appropriate cryptographic operations permits a document
author to require recipients to be granted access for all the labels
specified or for any of the labels specified. For example, the
designation (Accounting#example.com + Executive#example.com) might
indicate that a recipient must be a member of the Accounting and
Executive teams while the designation (Accounting#example.com |
Executive#example.com) would enable members of either team to read
the material.
While the recryption algorithm used in Mesh/Recrypt allows the use of
conjunctions and disjunctions to implement the equivalent of an ACL
entry granting access, it is not possible to implement the equivalent
of an ACL entry denying access to a group of users. The recryption
service can be instructed to refuse recryption to a group of users
but this restriction is not cryptographically enforced.
Since users must request a recryption key from the recryption service
for each document accessed, the recryption service is a Policy
Control Point and is thus potentially a point at which additional
accountability and/or access controls may be introduced. An
enterprise recryption service might maintain a log of all access
requests from users and restrict access to users whose requests
exceed some form of quota. Attempts to access particularly sensitive
documents might raise flags requiring review by a supervisor.
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3.6. Multiple Devices
When the S/MIME and OpenPGP email encryption schemes were developed
in the 1990s the machines of the day, if movable at all were
?portable? rather than ?mobile?. Contemporary users demand access to
their communications applications from a wide variety of devices
including desktops, laptops, tablets, phones and even watches. The
need for a single user to access their email on multiple devices is
now the norm rather than the exception.
Use of multiple devices and in particular mobile devices introduces
obvious security concerns. A device may be lost or stolen; a machine
may be sold without destroying data stored on it. Such circumstances
very frequently result in disclosure of private keys to an attacker.
Maintaining separate private keys on each device allows the
consequences of such loss to be mitigated and further compromise
prevented.
To apply recryption to this use case, the email recipient establishes
a personal recryption keyset on a machine that they consider at least
risk of compromise. A separate recryption key entry is then created
for each device and the recryption keyset uploaded to a suitable
recryption server host (e.g. the presence service of a chat
application, inbound mail server, etc.)
One difficulty that arises in this approach is that while a non-
transitive recryption mechanism can be applied in either a sender
side context such as a mailing list or a receiver side context such
as supporting multiple devices, enabling the use of both at the same
time requires additional effort.
4. Mesh/Recrypt/Admin Service
The Mesh/Recrypt administration service supports transactions to Add
and Delete members from a group and to list all the members in a
group.
_recrypt._tcp
/.well-known/recrypt
Every Recrypt Service transaction consists of exactly one request
followed by exactly one response.
Mesh Service transactions MAY cause modification of the data stored
in the Mesh Portal or the Mesh itself but do not cause changes to the
connection state. The protocol itself is thus idempotent. There is
no set sequence in which operations are required to be performed. It
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is not necessary to perform a Hello transaction prior to a
CreateGroup, AddMember or any other transaction.
4.1. Request Messages
A Mesh/Recrypt administration Service request consists of a payload
object that inherits from the MeshRequest class. When using the HTTP
binding, the request MUST specify the portal DNS address in the HTTP
Host field.
4.1.1. Message: RecryptRequest
Base class for all request messages.
[None]
4.2. Response Messages
A Mesh/Recrypt administration Service response consists of a payload
object that inherits from the MeshResponse class. When using the
HTTP binding, the response SHOULD report the Status response code in
the HTTP response message. However the response code returned in the
payload object MUST always be considered authoritative.
4.2.1. Message: RecryptResponse
Base class for all response messages. Contains only the status code
and status description fields.
[None]
4.3. Imported Objects
The Recrypt Administration Sercice makes use of JSON objects defined
in the JOSE Signatgure and Encryption specifications.
4.4. Common classes
The following classes are referenced at multiple points in the
protocol.
4.4.1. Structure: RecryptionGroup
Describes a group of recryption users.
String (Optional)
A user friendly account name in RFC821 format (user@example.com).
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MemberEntry [0..Many]
Member of a recryption group
PublicKey [0..Many]
The set of past encryption keys associated with the group.
PublicKey (Optional)
The current group encryption key
4.4.2. Structure: MemberEntry
Describes a member of a recryption group
String (Optional)
UDF fingerprint of the user's master profile
String (Optional)
User friendly account name
String [0..Many]
A list of privileges assigned to the user.
Currently defined privileges are RECRYPT, ADMIN and SUPER. Recrypt
grants a user the right to request decryption of data encrypted under
the group key. ADMIN grants the right to add or remove users from
the group. SUPER grants the right to add or remove administrators
and super-administrators from the group.
Note that being granted the necessary privilege does not in itself
confer the ability to decrypt messages as this requires access to the
master private key.
String [0..Many]
A list of quotas assigned to the user.
Each quota is described by the UDF fingerprint of the quota service.
String (Optional)
Member status. Valid values are ACTIVE, REVOKED and SUSPENDED.
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Once added to a recryption group, a user can never be 'deleted'.
Instead their member record is marked as REVOKED or SUSPENDED which
causes the recryption service to refuse further recryption requests.
Note that it is entirely valid for newly created recryption group to
contain member entries that are inactive. This allows a key
administrator to generate key material for group members in
anticipation of them requiring access without immediately granting
that access.
UserDecryptionEntry [0..Many]
Identifier of
4.4.3. Structure: UserDecryptionEntry
Decryption entry for a particular user and group key
String (Optional)
Fingerprint of the encryption key to which this recryption data
corresponds
String (Optional)
Fingerprint of the user's key
String (Optional)
A user friendly account name in RFC821 format (user@example.com).
PublicKey (Optional)
The recryption key to be used to recrypt for this user.
JoseWebEncryption (Optional)
The user's decryption key encrypted under a one or more encryption
keys held by the user. The encrypted content is a PrivateKey
structure specifying the decryption key for the user.
4.4.4. Structure: CombinedToGroup
Glue that maps a combined key identifier (Encryption, Member) to a
group and member entry.
String (Optional)
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Fingerprint of the encryption key to which this recryption data
corresponds
String (Optional)
Fingerprint of the user's key
String (Optional)
UDF fingerprint of the user's master profile
String (Optional)
A user friendly account name in RFC821 format (user@example.com).
4.5. Administrator Transactions
4.6. Transaction: Hello
Request: HelloRequest
Response: HelloResponse
Report service and version information.
The Hello transaction provides a means of determining which protocol
versions, message encodings and transport protocols are supported by
the service.
4.7. Transaction: CreateGroup
Request: CreateGroupRequest
Response: CreateGroupResponse
Create a new recryption group.
4.7.1. Message: CreateGroupRequest
o Inherits: RecryptRequest
Request creation of a recryption group. The only request parameter
describes the group to be created.
RecryptionGroup (Optional)
The Recryption Group to create
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4.7.2. Message: CreateGroupResponse
o Inherits: RecryptResponse
Reports the success or failure of a CreateGroup request. The
operation either succeeds or fails, there are no returned parameters
[None]
4.8. Transaction: UpdateGroup
Request: UpdateGroupRequest
Response: UpdateGroupResponse
Update the information describing a recryption group.
4.8.1. Message: UpdateGroupRequest
o Inherits: RecryptRequest
Request an update to a recryption group.
Note that the update process is currently limited to 'strike and
replace'. This is likely to become cumbersome if groups with very
large numbers of entries are being maintained. It is likely that a
future version of the protocol will support update requests that
implement commonly occurring tasks such as updates to add a new
encryption key, etc.
RecryptionGroup (Optional)
The Recryption Group to create
4.8.2. Message: UpdateGroupResponse
o Inherits: RecryptResponse
Reports the success or failure of a UpdateGroup request. The
operation either succeeds or fails, there are no returned parameters
[None]
4.9. Transaction: AddMember
Request: AddMemberRequest
Response: AddMemberResponse
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Add a member or members to an existing recryption group.
4.9.1. Message: AddMemberRequest
o Inherits: RecryptRequest
String (Optional)
The UDF fingerprint of the recryption group to add the member to.
MemberEntry [0..Many]
Describes the member(s) to add
4.9.2. Message: AddMemberResponse
o Inherits: RecryptResponse
Reports the success or failure of a AddMember request. The operation
either succeeds or fails, there are no returned parameters
[None]
4.10. Transaction: UpdateMember
Request: UpdateMemberRequest
Response: UpdateMemberResponse
Update a one or more member entries
This transaction may be used to make member entries inactive by
posting REVOKED or SUSPENDED status to their member entry.
4.10.1. Message: UpdateMemberRequest
o Inherits: RecryptRequest
String (Optional)
The UDF fingerprint of the recryption group in which the member
entries is to be updated
MemberEntry [0..Many]
Describes the member(s) to add
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4.10.2. Message: UpdateMemberResponse
o Inherits: RecryptResponse
Reports the success or failure of a UpdateMember request. The
operation either succeeds or fails, there are no returned parameters
[None]
4.11. Future work
At present the protocol does not provide a mechanism for modifying
administrator privileges or requesting statistics on use of
recryption services. These are obviously important. Whether these
should be part of the base protocol or a separate protocol is another
matter.
5. User Service
The only transaction supported by the user facing service at this
point is the ability to request a recryption operation.
5.1. Transaction: RecryptData
Request: RecryptDataRequest
Response: RecryptDataResponse
Request that the service provide a recryption result for the
specified encrypted data and return it encrypted under the user's
public key.
5.1.1. Message: RecryptDataRequest
o Inherits: RecryptRequest
Request that the service provide a recryption result for the
specified encrypted data and return it encrypted under the user's
public key.
String (Optional)
The recryption group in which the member entries is to be updated
Recipient (Optional)
The Jose Web Encryption recipient information to be partially
decrypted.
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5.1.2. Message: RecryptDataResponse
o Inherits: RecryptResponse
JoseWebEncryption (Optional)
The partial decryption information to use to complete the decryption
encrypted under the user's key.
JoseWebEncryption (Optional)
The decryption key to use to complete the decryption encrypted under
the user's key.
6. Acknowledgements
7. Implementation Status
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC6982]
[RFC6982] . The description of implementations in this section is
intended to assist the IETF in its decision processes in progressing
drafts to RFCs. Please note that the listing of any individual
implementation here does not imply endorsement by the IETF.
Furthermore, no effort has been spent to verify the information
presented here that was supplied by IETF contributors. This is not
intended as, and must not be construed to be, a catalog of available
implementations or their features. Readers are advised to note that
other implementations may exist.
According to [RFC6982] [RFC6982] , "this will allow reviewers and
working groups to assign due consideration to documents that have the
benefit of running code, which may serve as evidence of valuable
experimentation and feedback that have made the implemented protocols
more mature. It is up to the individual working groups to use this
information as they see fit".
7.1. Reference Implementation
Organization: Comodo Group Inc.
Implementer: Phillip Hallam-Baker
Maturity: Experimental Prototype
This implementation was used to produce the reference section and all
the examples in this document. Since the conversion of specification
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to code is automatic, there is a high degree of assurance that the
reference implementation is consistent with this document.
7.1.1. Coverage:
The draft-xx branch describes the code used to create version xx of
this document.
The main current limitations are that the code only supports RSA key
pairs and for ease of development the server does not persist keys
across sessions. Nor does the implementation currently support the
HTTP payload authentication and encryption layer or make use of TLS.
These could be easily fixed.
The client and server are implemented as libraries that may be called
from a multi-protocol server. A standalone server will be provided
in a future release.
Only the JSON encoding is currently implemented. The JSON-B, JSON-C,
ASN.1 and TLS Schema implementations are all supported by the code
generation tool but not currently implemented as the build tool
bindings for those encodings have not yet been finalized or
documented.
The key restrictions for TLS key exchange have not yet been
implemented.
The code has only been tested on Windows 10 but passed compatibility
testing for both Mono and dotNetCore 10 run times which should in
theory permit use on Linux and OSX platforms.
7.1.2. Licensing
The code is released under an MIT License
Source code is available from GitHub at
https://github.com/hallambaker/Mathematical-Mesh
7.1.3. Implementation Experience
The implementation and specification documentation were developed in
Visual Studio using the PHB Build Tools suite.
7.1.4. Contact Info
Contact Phillip Hallam-Baker phill@hallambaker.com
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8. Security Considerations
[This is just a sketch for the present.]
9. IANA Considerations
[TBS list out all the code points that require an IANA registration]
10. References
10.1. Normative References
[Blaze98] "[Reference Not Found!]".
[draft-hallambaker-mesh-architecture]
Hallam-Baker, P., "Mathematical Mesh: Architecture",
draft-hallambaker-mesh-architecture-03 (work in progress),
May 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997.
10.2. Informative References
[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", RFC 6982,
DOI 10.17487/RFC6982, July 2013.
Author's Address
Phillip Hallam-Baker
Comodo Group Inc.
Email: philliph@comodo.com
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