Internet DRAFT - draft-hallambaker-mesh-dare
draft-hallambaker-mesh-dare
Network Working Group P. M. Hallam-Baker
Internet-Draft ThresholdSecrets.com
Intended status: Informational 28 June 2023
Expires: 30 December 2023
Mathematical Mesh 3.0 Part III : Data At Rest Encryption (DARE)
draft-hallambaker-mesh-dare-17
Abstract
This document describes the Data At Rest Encryption (DARE) Envelope
and Sequence syntax.
The DARE Envelope syntax is used to digitally sign, digest,
authenticate, or encrypt arbitrary content data.
The DARE Sequence syntax describes an append-only sequence of
entries, each containing a DARE Envelope. DARE Sequences may support
cryptographic integrity verification of the entire data container
content by means of a Merkle tree.
[Note to Readers]
Discussion of this draft takes place on the MATHMESH mailing list
(mathmesh@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/search/?email_list=mathmesh.
This document is also available online at
http://mathmesh.com/Documents/draft-hallambaker-mesh-dare.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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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 30 December 2023.
Hallam-Baker Expires 30 December 2023 [Page 1]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Copyright Notice
Copyright (c) 2023 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
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Encryption and Integrity . . . . . . . . . . . . . . . . 5
1.1.1. Key Exchange . . . . . . . . . . . . . . . . . . . . 5
1.1.2. Data Erasure . . . . . . . . . . . . . . . . . . . . 6
1.2. Signature . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.1. Signing Individual Plaintext Envelopes . . . . . . . 7
1.2.2. Signing Individual Encrypted Envelopes . . . . . . . 7
1.2.3. Signing sequences of envelopes . . . . . . . . . . . 7
1.3. Sequence . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.1. Sequence Format . . . . . . . . . . . . . . . . . . . 8
1.3.2. Write . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.3. Encryption and Authentication . . . . . . . . . . . . 9
1.3.4. Integrity and Signature . . . . . . . . . . . . . . . 10
1.3.5. Redaction . . . . . . . . . . . . . . . . . . . . . . 10
1.3.6. Alternative approaches . . . . . . . . . . . . . . . 11
1.3.7. Efficiency . . . . . . . . . . . . . . . . . . . . . 11
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1. Related Specifications . . . . . . . . . . . . . . . . . 12
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 13
2.3. Defined terms . . . . . . . . . . . . . . . . . . . . . . 13
3. DARE Envelope Architecture . . . . . . . . . . . . . . . . . 14
3.1. Processing Considerations . . . . . . . . . . . . . . . . 15
3.2. Encoded Data Sequence . . . . . . . . . . . . . . . . . . 15
3.3. Content Metadata and Annotations . . . . . . . . . . . . 16
3.4. Encryption and Integrity . . . . . . . . . . . . . . . . 17
3.4.1. Key Exchange . . . . . . . . . . . . . . . . . . . . 18
3.4.2. Key Identifiers . . . . . . . . . . . . . . . . . . . 19
3.4.3. Salt Derivation . . . . . . . . . . . . . . . . . . . 19
3.4.4. Key Derivation . . . . . . . . . . . . . . . . . . . 20
3.5. Signature . . . . . . . . . . . . . . . . . . . . . . . . 21
3.6. Algorithms . . . . . . . . . . . . . . . . . . . . . . . 21
3.6.1. Field: kwd . . . . . . . . . . . . . . . . . . . . . 21
4. DARE Sequence Architecture . . . . . . . . . . . . . . . . . 21
4.1. Sequence Navigation . . . . . . . . . . . . . . . . . . . 21
4.1.1. Tree . . . . . . . . . . . . . . . . . . . . . . . . 22
Hallam-Baker Expires 30 December 2023 [Page 2]
Internet-Draft Mesh: Data At Rest Encryption June 2023
4.1.2. Position Index . . . . . . . . . . . . . . . . . . . 23
4.1.3. Metadata Index . . . . . . . . . . . . . . . . . . . 23
4.2. Integrity Mechanisms . . . . . . . . . . . . . . . . . . 23
4.2.1. Digest Chain calculation . . . . . . . . . . . . . . 23
4.2.2. Binary Merkle tree calculation . . . . . . . . . . . 24
4.2.3. Signature . . . . . . . . . . . . . . . . . . . . . . 24
5. DARE Schema . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.1. Envelope Classes . . . . . . . . . . . . . . . . . . . . 25
5.1.1. Structure: DareEnvelopeSequence . . . . . . . . . . . 25
5.2. Header and Trailer Classes . . . . . . . . . . . . . . . 25
5.2.1. Structure: DareTrailer . . . . . . . . . . . . . . . 25
5.2.2. Structure: DareHeader . . . . . . . . . . . . . . . . 26
5.2.3. Structure: ContentMeta . . . . . . . . . . . . . . . 27
5.3. Cryptographic Data . . . . . . . . . . . . . . . . . . . 28
5.3.1. Structure: DareSignature . . . . . . . . . . . . . . 28
5.3.2. Structure: IntervalSignature . . . . . . . . . . . . 29
5.3.3. Structure: SignedEnvelope . . . . . . . . . . . . . . 29
5.3.4. Structure: X509Certificate . . . . . . . . . . . . . 29
5.3.5. Structure: DareRecipient . . . . . . . . . . . . . . 30
5.3.6. Structure: DarePolicy . . . . . . . . . . . . . . . . 30
5.3.7. Structure: FileEntry . . . . . . . . . . . . . . . . 31
5.3.8. Structure: Witness . . . . . . . . . . . . . . . . . 31
5.3.9. Structure: Proof . . . . . . . . . . . . . . . . . . 31
6. DARE Container Schema . . . . . . . . . . . . . . . . . . . . 32
6.1. Container Headers . . . . . . . . . . . . . . . . . . . . 32
6.1.1. Structure: SequenceInfo . . . . . . . . . . . . . . . 32
6.2. Index Structures . . . . . . . . . . . . . . . . . . . . 33
6.2.1. Structure: SequenceIndex . . . . . . . . . . . . . . 33
6.2.2. Structure: IndexPosition . . . . . . . . . . . . . . 33
6.2.3. Structure: KeyValue . . . . . . . . . . . . . . . . . 33
7. Dare Sequence Applications . . . . . . . . . . . . . . . . . 33
7.1. Catalog . . . . . . . . . . . . . . . . . . . . . . . . . 34
7.2. Spool . . . . . . . . . . . . . . . . . . . . . . . . . . 34
7.3. Archive . . . . . . . . . . . . . . . . . . . . . . . . . 35
8. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 35
8.1. Terminal integrity check . . . . . . . . . . . . . . . . 35
8.2. Terminal index record . . . . . . . . . . . . . . . . . . 35
8.3. Deferred indexing . . . . . . . . . . . . . . . . . . . . 36
9. Security Considerations . . . . . . . . . . . . . . . . . . . 36
9.1. Encryption/Signature nesting . . . . . . . . . . . . . . 36
9.2. Side channel . . . . . . . . . . . . . . . . . . . . . . 36
9.3. Salt reuse . . . . . . . . . . . . . . . . . . . . . . . 36
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36
12. Appendix A: DARE Envelope Examples and Test Vectors . . . . . 36
13. Test Examples . . . . . . . . . . . . . . . . . . . . . . . . 36
13.1. Plaintext Message . . . . . . . . . . . . . . . . . . . 37
13.2. Plaintext Message with EDS . . . . . . . . . . . . . . . 37
Hallam-Baker Expires 30 December 2023 [Page 3]
Internet-Draft Mesh: Data At Rest Encryption June 2023
13.3. Encrypted Message . . . . . . . . . . . . . . . . . . . 38
13.4. Signed Message . . . . . . . . . . . . . . . . . . . . . 39
13.5. Signed and Encrypted Message . . . . . . . . . . . . . . 40
14. Appendix B: DARE Sequence Examples and Test Vectors . . . . . 41
14.1. Simple sequence . . . . . . . . . . . . . . . . . . . . 41
14.2. Payload and chain digests . . . . . . . . . . . . . . . 42
14.3. Merkle Tree . . . . . . . . . . . . . . . . . . . . . . 44
14.4. Signed sequence . . . . . . . . . . . . . . . . . . . . 48
14.5. Encrypted sequence . . . . . . . . . . . . . . . . . . . 49
15. Appendix C: Previous Frame Function . . . . . . . . . . . . . 54
16. Appendix D: Outstanding Issues . . . . . . . . . . . . . . . 54
17. Normative References . . . . . . . . . . . . . . . . . . . . 55
18. Informative References . . . . . . . . . . . . . . . . . . . 57
1. Introduction
This document describes the Data At Rest Encryption (DARE) Envelope
and Sequence Syntax. The DARE Envelope syntax is used to digitally
sign, digest, authenticate, or encrypt arbitrary message content.
The DARE Sequence syntax describes an append-only sequence of data
frames, each containing a DARE Envelope that supports efficient
incremental signature and encryption.
The DARE Envelope Syntax is based on a subset of the JSON Web
Signature [RFC7515] and JSON Web Encryption [RFC7516] standards and
shares many fields and semantics. The processing model and data
structures have been streamlined to remove alternative means of
specifying the same content and to enable multiple data sequences to
be signed and encrypted under a single master encryption key without
compromise to security.
A DARE Envelope consists of a _Header_, _Payload_ and an optional
_Trailer_. To enable single pass encoding and decoding, the Header
contains all the information required to perform cryptographic
processing of the Payload and authentication data (digest, MAC,
signature values) MAY be deferred to the Trailer section.
A DARE Sequence is an append-only log format consisting of a sequence
of frames. Cryptographic enhancements (signature, encryption) may be
applied to individual frames or to sets of frames. Thus, a single
key exchange may be used to provide a master key to encrypt multiple
frames and a single signature may be used to authenticate all the
frames in the container up to and including the frame in which the
signature is presented.
Hallam-Baker Expires 30 December 2023 [Page 4]
Internet-Draft Mesh: Data At Rest Encryption June 2023
The DARE Envelope syntax may be used either as a standalone
cryptographic message syntax or as a means of presenting a single
DARE Sequence frame together with the complete cryptographic context
required to verify the contents and decrypt them.
1.1. Encryption and Integrity
A key innovation in the DARE Envelope Syntax is the separation of key
exchange and data encryption operations so that a Master Key (MK)
established in a single exchange to be applied to multiple data
sequences. This means that a single public key operation MAY be used
to encrypt and/or authenticate multiple parts of the same DARE
Envelope or multiple frames in a DARE Sequence.
To avoid reuse of the key and to avoid the need to communicate
separate IVs, each octet sequence is encrypted under a different
encryption key (and IV if required) derived from the Master Key by
means of a salt that is unique for each octet sequence that is
encrypted. The same approach is used to generate keys for
calculating a MAC over the octet sequence if required. This approach
allows encryption and integrity protections to be applied to the
envelope payload, to header or trailer fields or to application
defined Enhanced Data Sequences in the header or trailer.
1.1.1. Key Exchange
Traditional cryptographic containers describe the application of a
single key exchange to encryption of a single octet sequence.
Examples include PCKS#7/CMS [RFC2315], OpenPGP [RFC4880] and JSON Web
Encryption [RFC7516].
To encrypt data using RSA, the encoder first generates a random
encryption key and initialization vector (IV). The encryption key is
encrypted under the public key of each recipient to create a per-
recipient decryption entry. The encryption key, plaintext and IV are
used to generate the ciphertext (figure 1).
(Artwork only available as svg: No external link available, see
draft-hallambaker-mesh-dare-17.html for artwork.)
Figure 1: Monolithic Key Exchange and Encrypt
This approach is adequate for the task of encrypting a single octet
stream. It is less than satisfactory when encrypting multiple octet
streams or very long streams for which a rekeying operation is
desirable.
Hallam-Baker Expires 30 December 2023 [Page 5]
Internet-Draft Mesh: Data At Rest Encryption June 2023
In the DARE approach, key exchange and key derivation are separate
operations and keys MAY be derived for encryption or integrity
purposes or both. A single key exchange MAY be used to derive keys
to apply encryption and integrity enhancements to multiple data
sequences.
The DARE key exchange begins with the same key exchange used to
produce the CEK in JWE but instead of using the CEK to encipher data
directly, it is used as one of the inputs to a Key Derivation
Function (KDF) that is used to derive parameters for each block of
data to be encrypted. To avoid the need to introduce additional
terminology, the term 'CEK' is still used to describe the output of
the key agreement algorithm (including key unwrapping if required)
but it is more appropriately described as a Master Key (figure 2).
(Artwork only available as svg: No external link available, see
draft-hallambaker-mesh-dare-17.html for artwork.)
Figure 2: Exchange of Master Key
A Master Key may be used to encrypt any number of data items. Each
data item is encrypted under a different encryption key and IV (if
required). This data is derived from the Master Key using the HKDF
function [RFC5869] using a different salt for each data item and
separate info tags for each cryptographic function (figure 3).
(Artwork only available as svg: No external link available, see
draft-hallambaker-mesh-dare-17.html for artwork.)
Figure 3: Data item encryption under Master Key and per-item salt.
This approach to encryption offers considerably greater flexibility
allowing the same format for data item encryption to be applied at
the transport, message or field level.
1.1.2. Data Erasure
Each encrypted DARE Envelope specifies a unique Master Salt value of
at least 128 bits which is used to derive the salt values used to
derive cryptographic keys for the envelope payload and annotations.
Erasure of the Master Salt value MAY be used to effectively render
the envelope payload and annotations undecipherable without altering
the envelope payload data. The work factor for decryption will be
O(2^128) even if the decryption key is compromised.
Hallam-Baker Expires 30 December 2023 [Page 6]
Internet-Draft Mesh: Data At Rest Encryption June 2023
1.2. Signature
As with encryption, DARE Envelope signatures MAY be applied to an
individual envelope or a sequence of envelope.
1.2.1. Signing Individual Plaintext Envelopes
When an individual plaintext envelope is signed, the digest value
used to create the signature is calculated over the binary value of
the payload data. That is, the value of the payload before the
encoding (Base-64, JSON-B) is applied.
1.2.2. Signing Individual Encrypted Envelopes
When an individual plaintext envelope is signed, the digest value
used to create the signature is calculated over the binary value of
the payload data. That is, the value of the payload after encryption
but before the encoding (Base-64, JSON-B) is applied.
Use of signing and encryption in combination presents the risk of
subtle attacks depending on the order in which signing and encryption
take place [Davis2001].
Na?ve approaches in which an envelope is encrypted and then signed
present the possibility of a surreptitious forwarding attack. For
example, Alice signs an envelope and sends it to Mallet who then
strips off Alice's signature and sends the envelope to Bob.
Na?ve approaches in which an envelope is signed and then encrypted
present the possibility of an attacker claiming authorship of a
ciphertext. For example, Alice encrypts a ciphertext for Bob and
then signs it. Mallet then intercepts the envelope and sends it to
Bob.
While neither attack is a concern in all applications, both attacks
pose potential hazards for the unwary and require close inspection of
application protocol design to avoid exploitation.
To prevent these attacks, each signature on an envelope that is
signed and encrypted MUST include a witness value that is calculated
by applying a MAC function to the signature value as described in
section XXX.
1.2.3. Signing sequences of envelopes
To sign multiple envelopes with a single signature, we first
construct a Merkle tree of the envelope payload digest values and
then sign the root of the Merkle tree.
Hallam-Baker Expires 30 December 2023 [Page 7]
Internet-Draft Mesh: Data At Rest Encryption June 2023
[This is not yet implemented but will be soon.]
1.3. Sequence
DARE Sequence is a message and file syntax that allows a sequence of
data frames to be represented with cryptographic integrity,
signature, and encryption enhancements to be constructed in an append
only format.
The format is designed to meet the requirements of a wide range of
use cases including:
* Recording transactions in persistent storage.
* Synchronizing transaction logs between hosts.
* File archive.
* Message spool.
* Signing and encrypting single data items.
* Incremental encryption and authentication of server logs.
1.3.1. Sequence Format
A Sequence consists of a sequence of variable length Frames. Each
frame consists of a forward length indicator, the framed data and a
reverse length indicator. The reverse length indicator is written
out backwards allowing the length and thus the frame to be read in
the reverse direction:
(Artwork only available as svg: No external link available, see
draft-hallambaker-mesh-dare-17.html for artwork.)
Figure 4: JBCD Bidirectional Frame
Each frame contains a single DARE Envelope consisting of a Header,
Payload and Trailer (if required). The first frame in a container
describes the container format options and defaults. These include
the range of encoding options for frame metadata supported and the
container profiles to which the container conforms.
All internal data formats support use of pointers of up to 64 bits
allowing containers of up to 18 exabytes to be written.
Five container types are currently specified:
Hallam-Baker Expires 30 December 2023 [Page 8]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Simple The container does not provide any index or content integrity
checks.
Tree Frame headers contain entries that specify the start position
of previous frames at the apex of the immediately enclosing binary
tree. This enables efficient random access to any frame in the
file.
Digest Each frame trailer contains a PayloadDigest field.
Modification of the payload will cause verification of the
PayloadDigest value to fail on that frame.
Chain Each frame trailer contains PayloadDigest and ChainDigest
fields allowing modifications to the payload data to be detected.
Modification of the payload will cause verification of the
PayloadDigest value to fail on that frame and verification of the
ChainDigest value to fail on all subsequent frames.
Merkle Tree Frame headers contain entries that specify the start
position of previous frames at the apex of the immediately
enclosing binary tree. Frame Trailers contain TreeDigestPartial
and TreeDigestFinal entries forming a Merkle digest tree.
Currently, the Mesh only makes use of the Merkle Tree sequence type.
1.3.2. Write
In normal circumstances, Sequences are written as an append only log.
As with Envelopes, integrity information (payload digest, signatures)
is written to the entry trailer. Thus, large payloads may be written
without the need to buffer the payload data _provided that_ the
content length is known in advance.
Should exceptional circumstances require, Sequence entries MAY be
erased by overwriting the Payload and/or parts of the Header content
without compromising the ability to verify other entries in the
container. If the entry Payload is encrypted, it is sufficient to
erase the container salt value to render the container entry
effectively inaccessible (though recovery might still be possible if
the original salt value can be recovered from the storage media.
1.3.3. Encryption and Authentication
Frame payloads and associated attributes MAY be encrypted and/or
authenticated in the same manner as Envelopes.
Hallam-Baker Expires 30 December 2023 [Page 9]
Internet-Draft Mesh: Data At Rest Encryption June 2023
_Incremental encryption_ is supported allowing encryption parameters
from a single public key exchange operation to be applied to encrypt
multiple frames. The public key exchange information is specified in
the first encrypted frame and subsequent frames encrypted under those
parameters specify the location at which the key exchange information
is to be found by means of the ExchangePosition field which MUST
specify a location that is earlier in the file.
To avoid cryptographic vulnerabilities resulting from key re-use, the
DARE key exchange requires that each encrypted sequence use an
encryption key and initialization vector derived from the master key
established in the public key exchange by means of a unique salt
specified in each envelope.
Each Envelope and by extension, each Sequence frame MUST specify a
unique salt value of at least 128 bits. Since the encryption key is
derived from the salt value by means of a Key Derivation Function,
erasure of the salt MAY be used as a means of rendering the payload
plaintext value inaccessible without changing the payload value.
1.3.4. Integrity and Signature
Signatures MAY be applied to a payload digest, the final digest in a
chain or tree. The chain and tree digest modes allow a single
signature to be used to authenticate all frame payloads in a
container.
The tree signature mode is particularly suited to applications such
as file archives as it allows files to be verified individually
without requiring the signer to sign each individually. Furthermore,
in applications such as code signing, it allows a single signature to
be used to verify both the integrity of the code and its membership
of the distribution.
As with DARE Envelope, the signature mechanism does not specify the
interpretation of the signature semantics. The presence of a
signature demonstrates that the holder of the private key applied it
to the specified digest value but not their motive for doing so.
Describing such semantics is beyond the scope of this document and is
deferred to future work.
1.3.5. Redaction
The chief disadvantage of using an append-only format is that
containers only increase in size. In many applications, much of the
data in the container becomes redundant or obsolete and a process
analogous to garbage collection is required. This process is called
_redaction_.
Hallam-Baker Expires 30 December 2023 [Page 10]
Internet-Draft Mesh: Data At Rest Encryption June 2023
The simplest method of redaction is to create a new container and
sequentially copy each entry from the old container to the new,
discarding redundant frames and obsolete header information.
For example, partial index records may be consolidated into a single
index record placed in the last frame of the container. Unnecessary
signature and integrity data may be discarded and so on.
While redaction could in principle be effected by moving data in-
place in the existing container, supporting this approach in a robust
fashion is considerably more complex as it requires backward
references in subsequent frames to be overridden as each frame is
moved.
1.3.6. Alternative approaches
Many file proprietary formats are in use that support some or all of
these capabilities but only a handful have public, let alone open,
standards. DARE Sequence is designed to provide a superset of the
capabilities of existing message and file syntaxes, including:
* Cryptographic Message Syntax [RFC5652] defines a syntax used to
digitally sign, digest, authenticate, or encrypt arbitrary message
content.
* The.ZIP File Format specification [ZIPFILE] developed by Phil
Katz.
* The BitCoin Block chain [BLOCKCHAIN].
* JSON Web Encryption and JSON Web Signature
Attempting to make use of these specifications in a layered fashion
would require at least three separate encoders and introduce
unnecessary complexity. Furthermore, there is considerable overlap
between the specifications providing multiple means of achieving the
same ends, all of which must be supported if decoders are to work
reliably.
1.3.7. Efficiency
Every data format represents a compromise between different concerns,
in particular:
Compactness The space required to record data in the encoding.
Memory Overhead The additional volatile storage (RAM) required to
maintain indexes etc. to support efficient retrieval operations.
Hallam-Baker Expires 30 December 2023 [Page 11]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Number of Operations The number of operations required to retrieve
data from or append data to an existing encoded sequence.
Number of Disk Seek Operations Optimizing the response time of
magnetic storage media to random access read requests has
traditionally been one of the central concerns of database design.
The DARE Sequence format is designed to the assumption that this
will cease to be a concern as solid state media replaces magnetic.
While the cost of storage of all types has declined rapidly over the
past decades, so has the amount of data to be stored. DARE Sequence
represents a pragmatic balance of these considerations for current
technology. In particular, since payload volumes are likely to be
very large, memory and operational efficiency are considered higher
priorities than compactness.
2. Definitions
2.1. Related Specifications
The DARE Envelope and Sequence formats are based on the following
existing standards and specifications.
Object serialization The JSON-B [draft-hallambaker-jsonbcd] encoding
is used for object serialization. This encoding is an extension
of the JavaScript Object Notation (JSON) [RFC7159].
Message syntax The cryptographic processing model is based on JSON
Web Signature (JWS) [RFC7515], JSON Web Encryption (JWE) [RFC7516]
and JSON Web Key (JWK) [RFC7517].
Cryptographic primitives. The HMAC-based Extract-and-Expand Key
Derivation Function [RFC5869] and Advanced Encryption Standard
(AES) Key Wrap with Padding Algorithm [RFC3394] are used.
The Uniform Data Fingerprint method of presenting data digests is
used for key identifiers and other purposes
[draft-hallambaker-mesh-udf].
Cryptographic algorithms The cryptographic algorithms and
identifiers described in JSON Web Algorithms (JWA) [RFC7518] are
used together with additional algorithms as defined in the JSON
Object Signing and Encryption IANA registry [IANAJOSE].
Hallam-Baker Expires 30 December 2023 [Page 12]
Internet-Draft Mesh: Data At Rest Encryption June 2023
2.2. 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].
2.3. Defined terms
The terms "Authentication Tag", "Content Encryption Key", "Key
Management Mode", "Key Encryption", "Direct Key Agreement", "Key
Agreement with Key Wrapping" and "Direct Encryption" are defined in
the JWE specification [RFC7516].
The terms "Authentication", "Ciphertext", "Digital Signature",
"Encryption", "Initialization Vector (IV)", "Message Authentication
Code (MAC)", "Plaintext" and "Salt" are defined by the Internet
Security Glossary, Version 2 [RFC4949].
Annotated Envelope A DARE Envelope that contains an Annotations
field with at least one entry.
Authentication Data A Message Authentication Code or authentication
tag.
Complete Envelope A DARE envelope that contains the key exchange
information necessary for the intended recipient(s) to decrypt it.
Detached Envelope A DARE envelope that does not contain the key
exchange information necessary for the intended recipient(s) to
decrypt it.
Encryption Context The master key, encryption algorithms and
associated parameters used to generate a set of one or more
enhanced data sequences.
Encoded data sequence (EDS) A sequence consisting of a salt, content
data and authentication data (if required by the encryption
context).
Enhancement Applying a cryptographic operation to a data sequence.
This includes encryption, authentication and both at the same
time.
Generator The party that generates a DARE envelope.
Group Encryption Key A key used to encrypt data to be read by a
group of users. This is typically achieved by means of some form
of proxy re-encryption or distributed key generation.
Hallam-Baker Expires 30 December 2023 [Page 13]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Group Encryption Key Identifier A key identifier for a group
encryption key.
Master Key (MK) The master secret from which keys are derived for
authenticating enhanced data sequences.
Recipient Any party that receives and processes at least some part
of a DARE envelope.
Related Envelope A set of DARE envelopes that share the same key
exchange information and hence the same Master Key.
Uniform Data Fingerprint (UDF) The means of presenting the result of
a cryptographic digest function over a data sequence and content
type identifier specified in the Uniform Data Fingerprint
specification [draft-hallambaker-mesh-udf]
3. DARE Envelope Architecture
A DARE Envelope is a sequence of three parts:
Header A JSON object containing information a reader requires to
begin processing the envelope.
Payload An array of octets.
Trailer A JSON object containing information calculated from the
envelope payload.
For example, the following sequence is a JSON encoded Envelope with
an empty header, a payload of zero length and an empty trailer:
[ {}, "", {} ]
DARE Envelopes MAY be encoded using JSON serialization or a binary
serialization for greater efficiency.
JSON [RFC7159] Offers compatibility with applications and libraries
that support JSON. Payload data is encoded using Base64 incurring
a 33% overhead.
JSON-B [draft-hallambaker-jsonbcd] A superset of JSON encoding that
permits binary data to be encoded as a sequence of length-data
segments. This avoids the Base64 overhead incurred by JSON
encoding. Since JSON-B is a superset of JSON encoding, an
application can use a single decoder for either format.
JSON-C [draft-hallambaker-jsonbcd] A superset of JSON-C which
Hallam-Baker Expires 30 December 2023 [Page 14]
Internet-Draft Mesh: Data At Rest Encryption June 2023
provides additional efficiency by allowing field tags and other
repeated string data to be encoded by reference to a dictionary.
Since JSON-C is a superset of JSON and JSON-B encodings, an
application can use a single decoder for all three formats.
DARE Envelope processors MUST support JSON serialization and SHOULD
support JSON-B serialization.
3.1. Processing Considerations
The DARE Envelope Syntax supports single pass encoding and decoding
without buffering of data. All the information required to begin
processing a DARE envelope (key agreement information, digest
algorithms), is provided in the envelope header. All the information
that is derived from envelope processing (authentication codes,
digest values, signatures) is presented in the envelope trailer.
The choice of envelope encoding does not affect the semantics of
envelope processing. A DARE Envelope MAY be reserialized under the
same serialization or converted from any of the specified
serialization to any other serialization without changing the
semantics or integrity properties of the envelope.
3.2. Encoded Data Sequence
An encoded data sequence (EDS) is a sequence of octets that encodes a
data sequence according to cryptographic enhancements specified in
the context in which it is presented. An EDS MAY be encrypted and
MAY be authenticated by means of a MAC. The keys and other
cryptographic parameters used to apply these enhancements are derived
from the cryptographic context and a Salt prefix specified in the EDS
itself.
An EDS sequence contains exactly three binary fields encoded in
JSON-B serialization as follows:
Salt Prefix A sequence of octets used to derive the encryption key,
Initialization Vector and MAC key as required.
Body The plaintext or encrypted content.
Authentication Tag The authentication code value in the case that
the cryptographic context specifies use of authenticated
encryption or a MAC, otherwise is a zero-length field.
Requiring all three fields to be present, even in cases where they
are unnecessary simplifies processing at the cost of up to six
additional data bytes.
Hallam-Baker Expires 30 December 2023 [Page 15]
Internet-Draft Mesh: Data At Rest Encryption June 2023
The encoding of the 'From' header of the previous example as a
plaintext EDS is as follows:
88 01
00
88 17
46 72 6f 6d 3a 20 41 6c 69 63 65 40 65 78 61 6d
70 6c 65 2e 63 6f 6d
[EOF]
3.3. Content Metadata and Annotations
A header MAY contain header fields describing the payload content.
These include:
ContentType Specifies the IANA Media Type [RFC6838].
Annotations A list of Encoded Data Sequences that provide
application specific annotations to the envelope.
For example, consider the following mail message:
From: Alice@example.com
To: bob@example.com
Subject: TOP-SECRET Product Launch Today!
The CEO told me the product launch is today. Tell no-one!
Existing encryption approaches require that header fields such as the
subject line be encrypted with the body of the message or not
encrypted at all. Neither approach is satisfactory. In this
example, the subject line gives away important information that the
sender probably assumed would be encrypted. But if the subject line
is encrypted together with the message body, a mail client must
retrieve at least part of the message body to provide a 'folder'
view.
The plaintext form of the equivalent DARE Message encoding is:
Hallam-Baker Expires 30 December 2023 [Page 16]
Internet-Draft Mesh: Data At Rest Encryption June 2023
[{
"annotations":["iAEAiBdGcm9tOiBBbGljZUBleGFtcGxlLmNvbQ",
"iAEBiBNUbzogYm9iQGV4YW1wbGUuY29t",
"iAECiClTdWJqZWN0OiBUT1AtU0VDUkVUIFByb2R1Y3QgTGF1bmNoIFRvZG
F5IQ"
],
"ContentMetaData":"ewogICJjdHkiOiAiYXBwbGljYXRpb24vZXhhbXBsZS
1tYWlsIn0"},
"VGhlIENFTyB0b2xkIG1lIHRoZSBwcm9kdWN0IGxhdW5jaCBpcyB0b2RheS4gVG
VsbCBuby1vbmUh"
]
This contains the same information as before but the data we might
wish to encrypt to protect the confidentiality of the payload is
separated from data required for processing.
3.4. Encryption and Integrity
Encryption and integrity protections MAY be applied to any DARE
Envelope Payload and Annotations.
The following is an encrypted version of the message shown earlier.
The payload and annotations have both increased in size as a result
of the block cipher padding. The header now includes Recipients and
Salt fields to enable the content to be decoded.
Hallam-Baker Expires 30 December 2023 [Page 17]
Internet-Draft Mesh: Data At Rest Encryption June 2023
[{
"enc":"A256CBC",
"kid":"EBQA-GAWN-XMQL-SQAG-VNRL-XTLP-JFCN",
"Salt":"3eEtrAnN4wfdDvfQoD-Y7w",
"annotations":["iAEAiCAgp-PQwlQ7f5GQh6XN1bgDr5ltT9aY-egyRw6sOI
BRsw",
"iAEBiCDCH54KTiA3j_neZDlvR3IsUsNRh0NvAtKwz4UuNwCWNw",
"iAECiDB91pAwNeqAuIEvnb0c-u0sE8By2XrHSuzoqhZcpmoA-j80i_mD2x
2ASQwZ0x4EXQY"
],
"recipients":[{
"kid":"MDFQ-C642-7ZJ6-WVCA-QHPW-236B-UNCE",
"epk":{
"PublicKeyECDH":{
"crv":"Ed25519",
"Public":"GWX6yECOK50Sm9mLnnyjHazMufTLEnAYlut3Lsz5QXQ"}},
"wmk":"MF2WlbwIgGWlQWGevcy5OGyLnnu1CBQqHoAlq162sl3mb_wu8B
k1-g"}
],
"ContentMetaData":"ewogICJjdHkiOiAiYXBwbGljYXRpb24vZXhhbXBsZS
1tYWlsIn0"},
"4lTvJ9UGNlBVMHBN_e6yk2m4cQldY6eqEBjZh7n00I_hzybzfrTJVJ3qoZuYLU
em6695poMg0Kh6ny8i7cL4AA"
]
For efficiency of processing, the ContentMetaData is presented in
plaintext. This header could be encrypted as an EDS sequence and
presented as a cloaked header.
3.4.1. Key Exchange
The DARE key exchange is based on the JWE key exchange except that
encryption modes are intentionally limited and the output of the key
exchange is the DARE Master Key rather than the Content Encryption
Key.
A DARE Key Exchange MAY contain any number of Recipient entries, each
providing a means of decrypting the Master Key using a different
private key.
If the Key Exchange mechanism supports message recovery, Direct Key
Agreement is used, in all other cases, Key Wrapping is used.
Hallam-Baker Expires 30 December 2023 [Page 18]
Internet-Draft Mesh: Data At Rest Encryption June 2023
This approach allows envelopes with one intended recipient to be
handled in the exact same fashion as envelopes with multiple
recipients. While this does require an additional key wrapping
operation, that could be avoided if an envelope has exactly one
intended recipient, this is offset by the reduction in code
complexity.
If the key exchange algorithm does not support message recovery (e.g.
Diffie Hellman and Elliptic Curve Diffie-Hellman), the HKDF Extract-
and-Expand Key Derivation Function is used to derive a master key
using the following info tag:
"dare-master" [64 61 72 65 2d 6d 61 73 74 65 72] Key derivation info
field used when deriving a master key from the output of a key
exchange.
The master key length is the maximum of the key size of the
encryption algorithm specified by the key exchange header, the key
size of the MAC algorithm specified by the key exchange header (if
used) and 256.
3.4.2. Key Identifiers
The JWE/JWS specifications define a kid field for use as a key
identifier but not how the identifier itself is constructed. All
DARE key identifiers are either UDF key fingerprints
[draft-hallambaker-mesh-udf] or Mesh/Recrypt Group Key Identifiers.
A UDF fingerprint is formed as the digest of an IANA content type and
the digested data. A UDF key fingerprint is formed with the content
type application/pkix-keyinfo and the digested data is the ASN.1 DER
encoded PKIX certificate keyInfo sequence for the corresponding
public key.
A Group Key Identifier has the form <fingerprint>@<domain>. Where
<fingerprint> is a UDF key fingerprint and <domain> is the DNS
address of a service that provides the encryption service to support
decryption by group members.
3.4.3. Salt Derivation
A Master Salt is a sequence of 16 or more octets that is specified in
the Salt field of the header.
The Master Salt is used to derive salt values for the envelope
payload and associated encoded data sequences as follows.
Payload Salt = Master Salt
Hallam-Baker Expires 30 December 2023 [Page 19]
Internet-Draft Mesh: Data At Rest Encryption June 2023
EDS Salt = Concatenate (Payload Salt Prefix, Master Salt)
Encoders SHOULD NOT generate salt values that exceed 1024 octets.
The salt value is opaque to the DARE encoding but MAY be used to
encode application specific semantics including:
* Frame number to allow reassembly of a data sequence split over a
sequence of envelopes which may be delivered out of order.
* Transmit the Master Key in the manner of a Kerberos ticket.
* Identify the Master Key under which the Enhanced Data Sequence was
generated.
* Enable access to the plaintext to be eliminated by erasure of the
encryption key.
For data erasure to be effective, the salt MUST be constructed so
that the difficulty of recovering the key is sufficiently high that
it is infeasible. For most purposes, a salt with 128 bits of
appropriately random data is sufficient.
3.4.4. Key Derivation
Encryption and/or authentication keys are derived from the Master Key
using a Extract-and-Expand Key Derivation Function as follows:
0. The Master Key and salt value are used to extract the PRK
(pseudorandom key)
1. The PRK is used to derive the algorithm keys using the
application specific information input for that key type.
The application specific information inputs are:
"dare-encrypt" [64 61 72 65 2d 65 6e 63 72 79 70 74] To generate an
encryption or encryption with authentication key.
"dare-iv" [64 61 72 65 2d 65 6e 63 72 79 70 74] To generate an
initialization vector.
"dare-mac" [dare-mac] To generate a Message Authentication Code key.
Hallam-Baker Expires 30 December 2023 [Page 20]
Internet-Draft Mesh: Data At Rest Encryption June 2023
3.5. Signature
While encryption and integrity enhancements can be applied to any
part of a DARE Envelope, signatures are only applied to payload
digest values calculated over one or more envelope payloads.
The payload digest value for an envelope is calculated over the
binary payload data. That is, after any encryption enhancement has
been applied but before the envelope encoding is applied. This
allows envelopes to be converted from one encoding to another without
affecting signature verification.
Single Payload The signed value is the payload digest of the
envelope payload.
Multiple Payload. The signed value is the root of a Merkle Tree in
which the payload digest of the envelope is one of the leaves.
Verification of a multiple payload signature naturally requires the
additional digest values required to construct the Merkle Tree.
These are provided in the Trailer in a format that permits multiple
signers to reference the same tree data.
3.6. Algorithms
3.6.1. Field: kwd
The key wrapping and derivation algorithms.
Since the means of public key exchange is determined by the key
identifier of the recipient key, it is only necessary to specify the
algorithms used for key wrapping and derivation.
The default (and so far only) algorithm is kwd-aes-sha2-256-256.
Advanced Encryption Standard (AES) Key Wrap with Padding Algorithm
[RFC3394] is used to wrap the Master Exchange Key. AES 256 is used.
HMAC-based Extract-and-Expand Key Derivation Function [RFC5869] is
used for key derivation. SHA-2-256 is used for the hash function.
4. DARE Sequence Architecture
4.1. Sequence Navigation
Three means of locating frames in a container are supported:
Sequential Access frames sequentially starting from the start or the
Hallam-Baker Expires 30 December 2023 [Page 21]
Internet-Draft Mesh: Data At Rest Encryption June 2023
end of the container.
Binary search Access any container frame by frame number in
_O(log_2(n)) time by means of a binary tree constructed while the
container is written._
Index Access and container frame by frame number or by key by means
of an index record.
All DARE Sequences support sequential access. Only tree and Merkle
tree containers support binary search access. An index frame MAY be
written appended to any container and provides _O(1)_ access to any
frame listed in the index.
Two modes of compilation are considered:
Monolithic Frames are added to the container in a single operation,
e.g. file archives,
Incremental Additional frames are written to the container at
various intervals after it was originally created, e.g. server
logs, message spools.
In the monolithic mode, navigation requirements are best met by
writing an index frame to the end of the container when it is
complete. It is not necessary to construct a binary search tree
unless a Merkle tree integrity check is required.
In the incremental mode, Binary search provides an efficient means of
locating frames by frame number but not by key. Writing a complete
index to the container every _m_ write operations provides _O(m)_
search access but requires _O(n^2) storage._
Use of partial indexes provides a better compromise between speed and
efficiency. A partial index is written out every _m_ frames where
_m_ is a power of two. A complete index is written every time a
binary tree apex record is written. This approach provides for
_O(log_2(n)) search with incremental compilation with approximately
double the overhead of the monolithic case._
4.1.1. Tree
As previously described, the JBCD frame structure allows incremental
navigation to the immediately preceding frame. The TreePosition
parameter specifies the start position of _any_ previous frame in the
container, thus allowing rapid navigation to that point.
Hallam-Baker Expires 30 December 2023 [Page 22]
Internet-Draft Mesh: Data At Rest Encryption June 2023
The TreePosition parameter MAY be used to enable any frame in the
container to be retrieved in log_2(n) time by means of a binary
search. The TreePosition parameter specifies the immediately
preceding apex of a binary tree formed from the container entries.
For example, the TreePosition of frame 6 in a container gives the
location of frame 5, the TreePosition of frame 5 gives the location
of frame 3, the TreePosition of frame 3 gives the location of frame
1, and the TreePosition of frame 1 gives the location of frame 0:
(Artwork only available as svg: No external link available, see
draft-hallambaker-mesh-dare-17.html for artwork.)
Figure 5: Binary search tree.
An algorithm for efficiently calculating the immediately preceding
apex is provided in Appendix C.
4.1.2. Position Index
Contains a table of frame number, position pairs pointing to prior
locations in the file.
4.1.3. Metadata Index
Contains a list of IndexMeta entries. Each entry contains a metadata
description and a list of frame indexes (not positions) of frames
that match the description.
4.2. Integrity Mechanisms
Frame sequences in a DARE container MAY be protected against a frame
insertion attack by means of a digest chain, a binary Merkle tree or
both.
4.2.1. Digest Chain calculation
A digest chain is simple to implement but can only be verified if the
full chain of values is known. Appending a frame to the chain has
_O(1)_ complexity but verification has _O(n)_ complexity:
(Artwork only available as svg: No external link available, see
draft-hallambaker-mesh-dare-17.html for artwork.)
Figure 6: Hash chain integrity check
Hallam-Baker Expires 30 December 2023 [Page 23]
Internet-Draft Mesh: Data At Rest Encryption June 2023
The value of the chain digest for the first frame (frame 0) is
_H(H(null)+H(Payload_0)), where null is a zero length octet sequence
and payloadn is the sequence of payload data bytes for frame n_
The value of the chain digest for frame _n_ is _H(H(Payload_(n-1) +
H(Payloadn)), where A+B stands for concatenation of the byte
sequences A and B._
4.2.2. Binary Merkle tree calculation
The tree index mechanism describe earlier may be used to implement a
binary Merkle tree. The value TreeDigest specifies the apex value of
the tree for that node.
Appending a frame to the chain has _O(log_2 (n)) complexity provided
that the container format supports at least the binary tree index.
Verifying a chain has O(log2 (n)) complexity, provided that the set
of necessary digest inputs is known._
To calculate the value of the tree digest for a node, we first
calculate the values of all the sub trees that have their apex at
that node and then calculate the digest of that value and the
immediately preceding local apex.
4.2.3. Signature
Payload data MAY be signed using a JWS [RFC7515] as applied in the
Envelope.
Signatures are specified by the Signatures parameter in the content
header. The data that the signature is calculated over is defined by
the typ parameter of the Signature as follows.
Payload The value of the PayloadDigest parameter
Chain The value of the ChainDigest parameter
Tree The value of the TreeDigestFinal parameter
If the typ parameter is absent, the value Payload is implied.
A frame MAY contain multiple signatures created with the same signing
key and different typ values.
The use of signatures over chain and tree digest values permit
multiple frames to be validated using a single signature verification
operation.
Hallam-Baker Expires 30 December 2023 [Page 24]
Internet-Draft Mesh: Data At Rest Encryption June 2023
5. DARE Schema
A DARE Envelope consists of a Header, an Enhanced Data Sequence (EDS)
and an optional trailer. This section describes the JSON data fields
used to construct headers, trailers and complete envelopes.
Wherever possible, fields from JWE, JWS and JWK have been used. In
these cases, the fields have the exact same semantics. Note however
that the classes in which these fields are presented have different
structure and nesting.
5.1. Envelope Classes
A DARE envelope contains a single DAREMessageSequence in either the
JSON or Compact serialization as directed by the protocol in which it
is applied.
5.1.1. Structure: DareEnvelopeSequence
A DARE envelope containing Header, EDS and Trailer in JSON object
encoding. Since a DAREMessage is almost invariably presented in JSON
sequence or compact encoding, use of the DAREMessage subclass is
preferred.
Although a DARE envelope is functionally an object, it is serialized
as an ordered sequence. This ensures that the envelope header field
will always precede the body in a serialization, this allowing
processing of the header information to be performed before the
entire body has been received.
Header: DareHeader (Optional) The envelope header. May specify the
key exchange data, pre-signature or signature data, cloaked
headers and/or encrypted data sequences.
Body: Binary (Optional) The envelope body
Trailer: DareTrailer (Optional) The envelope trailer. If present,
this contains the signature.
5.2. Header and Trailer Classes
A DARE sequence MUST contain a (possibly empty) DAREHeader and MAY
contain a DARETrailer.
5.2.1. Structure: DareTrailer
A DARE envelope Trailer
Hallam-Baker Expires 30 December 2023 [Page 25]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Signatures: DareSignature [0..Many] A list of signatures. A
envelope trailer MUST NOT contain a signatures field if the header
contains a signatures field.
ApexSignatures: DareSignature [0..Many] A list of signatures over
the apex digest. A envelope trailer MUST NOT contain av apex
field if the header contains a signatures field.
SignedData: Binary (Optional) Contains a DAREHeader object
PayloadDigest: Binary (Optional) If present, contains the digest of
the Payload.
ChainDigest: Binary (Optional) If present, contains the digest of
the PayloadDigest values of this frame and the frame immediately
preceding.
TreeDigest: Binary (Optional) If present, contains the Binary Merkle
Tree digest value.
5.2.2. Structure: DareHeader
Inherits: DareTrailer
A DARE Envelope Header. Since any field that is present in a trailer
MAY be placed in a header instead, the envelope header inherits from
the trailer.
EnvelopeId: String (Optional) Unique identifier
EncryptionAlgorithm: String (Optional) The encryption algorithm as
specified in JWE
DigestAlgorithm: String (Optional) Digest Algorithm. If specified,
tells decoder that the digest algorithm is used to construct a
signature over the envelope payload.
KeyIdentifier: String (Optional) Base seed identifier.
Salt: Binary (Optional) Salt value used to derrive cryptographic
parameters for the content data.
Malt: Binary (Optional) Hash of the Salt value used to derrive
cryptographic parameters for the content data. This field SHOULD
NOT be present if the Salt field is present. It is used to allow
the salt value to be erased (thus rendering the payload content
irrecoverable) without affecting the ability to calculate the
payload digest value.
Hallam-Baker Expires 30 December 2023 [Page 26]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Cloaked: Binary (Optional) If present in a header or trailer,
specifies an encrypted data block containing additional header
fields whose values override those specified in the envelope and
context headers.
When specified in a header, a cloaked field MAY be used to conceal
metadata (content type, compression) and/or to specify an
additional layer of key exchange. That applies to both the
envelope body and to headers specified within the cloaked header.
Processing of cloaked data is described in...
EDSS: Binary [0..Many] If present, the Annotations field contains a
sequence of Encrypted Data Segments encrypted under the envelope
base seed. The interpretation of these fields is application
specific.
Recipients: DareRecipient [0..Many] A list of recipient key exchange
information blocks.
Policy: DarePolicy (Optional) A DARE security policy governing
future additions to the container.
ContentMetaData: Binary (Optional) If present contains a JSON
encoded ContentInfo structure which specifies plaintext content
metadata and forms one of the inputs to the envelope digest value.
SequenceInfo: SequenceInfo (Optional) Information that describes
container information
SequenceIndex: SequenceIndex (Optional) An index of records in the
current container up to but not including this one.
Received: DateTime (Optional) Date on which the envelope was
received.
Cover: Binary (Optional) HTML document containing cover text to be
presented if the document cannot be decrypted.
Bitmask: Binary (Optional) Bitmask used to identify a container
within a group for use in update notification etc.
Debug: String (Optional) Field reserved for use in debugging.
5.2.3. Structure: ContentMeta
UniqueId: String (Optional) Unique object identifier
Hallam-Baker Expires 30 December 2023 [Page 27]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Labels: String [0..Many] List of labels that are applied to the
payload of the frame.
KeyValues: KeyValue [0..Many] List of key/value pairs describing the
payload of the frame.
MessageType: String (Optional) The mesh message type
ContentType: String (Optional) The content type field as specified
in JWE
Paths: String [0..Many] List of filename paths for the payload of
the frame.
Filename: String (Optional) The original filename under which the
data was stored.
Event: String (Optional) Operation on the header
Created: DateTime (Optional) Initial creation date.
Modified: DateTime (Optional) Date of last modification.
Expire: DateTime (Optional) Date at which the associated transaction
will expire
First: Integer (Optional) Frame number of the first object instance
value.
Previous: Integer (Optional) Frame number of the immediately prior
object instance value
FileEntry: FileEntry (Optional) Information describing the file
entry on disk.
5.3. Cryptographic Data
DARE envelope uses the same fields as JWE and JWS but with different
structure. In particular, DARE envelopes MAY have multiple
recipients and multiple signers.
5.3.1. Structure: DareSignature
The signature value
Dig: String (Optional) Digest algorithm hint. Specifying the digest
algorithm to be applied to the envelope body allows the body to be
processed in streaming mode.
Hallam-Baker Expires 30 December 2023 [Page 28]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Alg: String (Optional) Key exchange algorithm
KeyIdentifier: String (Optional) Key identifier of the signature
key.
Certificate: X509Certificate (Optional) PKIX certificate of signer.
Path: X509Certificate (Optional) PKIX certificates that establish a
trust path for the signer.
Manifest: Binary (Optional) The data description that was signed.
SignatureValue: Binary (Optional) The signature value as an Enhanced
Data Sequence under the envelope base seed.
WitnessValue: Binary (Optional) The signature witness value used on
an encrypted envelope to demonstrate that the signature was
authorized by a party with actual knowledge of the encryption key
used to encrypt the envelope.
5.3.2. Structure: IntervalSignature
A digital signature over one or more envelopes consisting of an apex
signature value
Index: Integer (Optional) The index number of the frame containing
the apex signature.
Envelopes: SignedEnvelope (Optional) The signed envelopes in order,
lowest index first.
5.3.3. Structure: SignedEnvelope
An entry describing one signed envelope within an IntervalSignature
Index: Integer (Optional) The index number of the envelope.
Digest: Binary [0..Many] The digests required to complete the
verification of the signature.
5.3.4. Structure: X509Certificate
X5u: String (Optional) URL identifying an X.509 public key
certificate
X5: Binary (Optional) An X.509 public key certificate
Hallam-Baker Expires 30 December 2023 [Page 29]
Internet-Draft Mesh: Data At Rest Encryption June 2023
5.3.5. Structure: DareRecipient
Recipient information
KeyIdentifier: String (Optional) Key identifier for the encryption
key.
The Key identifier MUST be either a UDF fingerprint of a key or a
Group Key Identifier
KeyWrapDerivation: String (Optional) The key wrapping and derivation
algorithms.
WrappedBaseSeed: Binary (Optional) The wrapped base seed. The base
seed is encrypted under the result of the key exchange.
RecipientKeyData: String (Optional) The per-recipient key exchange
data.
5.3.6. Structure: DarePolicy
Public: Boolean (Optional) When applied to a store, indicates it is
world readable.
EncryptionAlgorithm: String (Optional) The encryption algorithm to
be used to compute the payload.
DigestAlgorithm: String (Optional) The digest algorithm to be used
to compute the payload digest.
Encryption: String (Optional) The encryption policy specifier,
determines how often a key exchange is required. 'Single': All
entries are encrypted under the key exchange specified in the
entry specifying this policy. 'Isolated': All entries are
encrypted under a separate key exchange. 'All': All entries are
encrypted. 'None': No entries are encrypted.
Default value is 'None' if EncryptKeys is null, and 'All'
otherwise.
Signature: String (Optional) The signature policy 'None': No entries
are signed. 'Last': The last entry in the container is signed.
'Isolated': All entries are independently signed. 'Any': Entries
may be signed.
Default value is 'None' if SignKeys is null, and 'Any' otherwise.
Sealed: Boolean (Optional) If true the policy is immutable and
Hallam-Baker Expires 30 December 2023 [Page 30]
Internet-Draft Mesh: Data At Rest Encryption June 2023
cannot be changed by a subsequent policy override.
5.3.7. Structure: FileEntry
Path: String (Optional) The file path in canonical form.
CreationTime: DateTime (Optional) The creation time of the file on
disk in UTC
LastAccessTime: DateTime (Optional) The last access time of the file
on disk in UTC
LastWriteTime: DateTime (Optional) The last write time of the file
on disk in UTC
Attributes: Integer (Optional) The file attribues as a bitmapped
integer.
5.3.8. Structure: Witness
Entry containing the latest apex value of a specified append only
log.
Id: String (Optional) Globally unique log identifier
Issuer: String (Optional) The issuer of the log
Apex: Binary (Optional) The Apex hash value
Index: Integer (Optional) Specifies the index number assigned to the
entry in the log.
5.3.9. Structure: Proof
Provides a proof that the payload with digest [hash] in the log
described by SignedWitness occurs at the index [Index]
SignedWitness: DareEnvelope (Optional) The signed apex under which
this proof chain is established
Hash: Binary (Optional)
Index: Integer (Optional) Specifies the index number assigned to the
entry in the log.
Path: Binary [0..Many] The list of entries from which the proof path
is computed.
Hallam-Baker Expires 30 December 2023 [Page 31]
Internet-Draft Mesh: Data At Rest Encryption June 2023
6. DARE Container Schema
TBS stuff
6.1. Container Headers
TBS stuff
6.1.1. Structure: SequenceInfo
Information that describes container information
DataEncoding: String (Optional) Specifies the data encoding for the
header section of for the following frames. This value is ONLY
valid in Frame 0 which MUST have a header encoded in JSON.
ContainerType: String (Optional) Specifies the container type for
the following records. This value is ONLY valid in Frame 0 which
MUST have a header encoded in JSON.
Index: Integer (Optional) The record index within the file. This
MUST be unique and satisfy any additional requirements determined
by the ContainerType.
IsMeta: Boolean (Optional) If true, the current frame is a meta
frame and does not contain a payload.
Note: Meta frames MAY be present in any container. Applications
MUST accept containers that contain meta frames at any position in
the file. Applications MUST NOT interpret a meta frame as a data
frame with an enpty payload.
Default: Boolean (Optional) If set true in a persistent container,
specifies that this record contains the default object for the
container.
TreePosition: Integer (Optional) Position of the frame containing
the apex of the preceding sub-tree.
IndexPosition: Integer (Optional) Specifies the position in the file
at which the last index entry is to be found
ExchangePosition: Integer (Optional) Specifies the position in the
file at which the key exchange data is to be found
Hallam-Baker Expires 30 December 2023 [Page 32]
Internet-Draft Mesh: Data At Rest Encryption June 2023
6.2. Index Structures
TBS stuff
6.2.1. Structure: SequenceIndex
A container index
Full: Boolean (Optional) If true, the index is complete and contains
position entries for all the frames in the file. If absent or
false, the index is incremental and only contains position entries
for records added since the last frame containing a
ContainerIndex.
Positions: IndexPosition [0..Many] List of container position
entries
6.2.2. Structure: IndexPosition
Specifies the position in a file at which a specified record index is
found
Index: Integer (Optional) The record index within the file.
Position: Integer (Optional) The record position within the file
relative to the index base.
UniqueId: String (Optional) Unique object identifier
6.2.3. Structure: KeyValue
Specifies a key/value entry
Key: String (Optional) The key
Value: String (Optional) The value corresponding to the key
7. Dare Sequence Applications
DARE Sequences are used to implement two forms of persistence store
to support Mesh operations:
Catalogs A set of related items which MAY be added, modified or
deleted at any time.
Spools A list of related items whose status MAY be changed at any
time but which are immutable once added.
Hallam-Baker Expires 30 December 2023 [Page 33]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Since DARE Sequences are an append only log format, entries can only
be modified or deleted by adding items to the log to change the
status of previous entries. It is always possible to undo any
operation on a catalog or spool unless the underlying container is
purged or the individual entries modified.
7.1. Catalog
Catalogs contain a set of entries, each of which is distinguished by
a unique identifier.
Three operations are supported:
Add Addition of the entry to the catalog
Update Modification of the data associated with the entry excluding
the identifier
Delete Removal of the entry from the catalog
The set of valid state transitions is defined by the Finite State
machine:
(Add-Update*-Delete)*
Catalogs are used to represent sets of persistent objects associated
with a Mesh Service Account. The user's set of contacts for example.
Each contact entry may be modified many times over time but refers to
the same subject for its entire lifetime.
7.2. Spool
Spools contain lists of entries, each of which is distinguished by a
unique identifier.
Four operations are supported:
Post Addition of the entry to the spool
Processed Marks the entry as having been processed.
Unprocessed Returns the entry to the unread state.
Delete Mark the entry as deleted allowing recovery of associated
storage in a subsequent purge operation.
The set of valid state transitions is defined by the Finite State
machine:
Hallam-Baker Expires 30 December 2023 [Page 34]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Post-(Processed| Unprocessed| Delete *)
Spools are used to represent time sequence ordered entries such as
lists of messages being sent or received, task queues and transaction
logs.
7.3. Archive
A DARE Archive is a DARE Sequence whose entries contain files. This
affords the same functionality as a traditional ZIP or tar archive
but with the added cryptographic capabilities provided by the DARE
format.
8. Future Work
The current specification describes an approach in which containers
are written according to a strict append-only policy. Greater
flexibility may be achieved by loosening this requirement allowing
record(s) at the end of the container to be overwritten.
8.1. Terminal integrity check
A major concern when operating a critical service is the possibility
of a hardware or power failure occurring during a write operation
causing the file update to be incomplete. While most modern
operating systems have effective mechanisms in place to prevent
corruption of the file system itself in such circumstances, this does
not provide sufficient protection at the application level.
Appending a null record containing a container-specific magic number
provides an effective means of detecting this circumstance that can
be quickly verified.
If a container specifies a terminal integrity check value in the
header of frame zero, the container is considered to be in an
incomplete write state if the final frame is not a null record
specifying the magic number.
When appending new records to such containers, the old terminal
integrity check record is overwritten by the data being added and a
new integrity check record appended to the end.
8.2. Terminal index record
A writer can maintain a complete (or partial) index of the container
in its final record without additional space overhead by overwriting
the prior index on each update.
Hallam-Baker Expires 30 December 2023 [Page 35]
Internet-Draft Mesh: Data At Rest Encryption June 2023
8.3. Deferred indexing
The task of updating terminal indexes may be deferred to a time when
the machine is not busy. This improves responsiveness and may avoid
the need to re-index containers receiving a sequence of updates.
This approach may be supported by appending new entries to the end of
the container in the usual fashion and maintaining a record of
containers to be updated as a separate task.
When updating the index on a container that has been updated in this
fashion, the writer must ensure that no data is lost even if the
process is interrupted. The use of guard records and other
precautions against loss of state is advised.
9. Security Considerations
This section describes security considerations arising from the use
of DARE in general applications.
Additional security considerations for use of DARE in Mesh services
and applications are described in the Mesh Security Considerations
guide [draft-hallambaker-mesh-security].
9.1. Encryption/Signature nesting
9.2. Side channel
9.3. Salt reuse
10. IANA Considerations
11. Acknowledgements
A list of people who have contributed to the design of the Mesh is
presented in [draft-hallambaker-mesh-architecture].
The name Data At Rest Encryption was proposed by Melhi Abdulhayo?lu.
12. Appendix A: DARE Envelope Examples and Test Vectors
13. Test Examples
In the following examples, Alice's encryption private key parameters
are:
Hallam-Baker Expires 30 December 2023 [Page 36]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"PrivateKeyECDH":{
"Private":"paX59ChSdnCUnAwmBYVFFqV5Cbr8g1A6iJ1axyQGFqk",
"crv":"Ed25519"}}
Alice's signature private key parameters are:
{
"PrivateKeyECDH":{
"Private":"hkYsLO2D7_4vuqZB3MFMV6blEozFJ5KL6CqBtu61Ops",
"crv":"Ed25519"}}
The body of the test message is the UTF8 representation of the
following string:
"This is a test long enough to require multiple blocks"
The EDS sequences, are the UTF8 representation of the following
strings:
"Subject: Message metadata should be encrypted"
"2018-02-01"
13.1. Plaintext Message
A plaintext message without associated EDS sequences is an empty
header followed by the message body:
{
"DareEnvelope":[{},
"VGhpcyBpcyBhIHRlc3QgbG9uZyBlbm91Z2ggdG8gcmVxdWlyZSBtdWx0aXBs
ZSBibG9ja3M"
]}
13.2. Plaintext Message with EDS
If a plaintext message contains EDS sequences, these are also in
plaintext:
{
"DareEnvelope":[{
"annotations":["iAEAiC1TdWJqZWN0OiBNZXNzYWdlIG1ldGFkYXRhIHNo
b3VsZCBiZSBlbmNyeXB0ZWQ",
"iAEBiAoyMDE4LTAyLTAx"
]},
"VGhpcyBpcyBhIHRlc3QgbG9uZyBlbm91Z2ggdG8gcmVxdWlyZSBtdWx0aXBs
ZSBibG9ja3M"
]}
Hallam-Baker Expires 30 December 2023 [Page 37]
Internet-Draft Mesh: Data At Rest Encryption June 2023
13.3. Encrypted Message
The creator generates a base seed:
6D C8 50 14 FD 8E EE B1 36 8F 2F E2 57 5B AE F7
00 2B F0 85 77 EC 84 55 9D A1 47 6B BC E8 8F 13
For each recipient of the message:
The creator generates an ephemeral key:
{
"PrivateKeyECDH":{
"Private":"IZZYwHMfhG0N038tWvORYOV_wTNw-MG6ueob3yXn6fk",
"crv":"Ed25519"}}
The key agreement value is calculated:
95 7D 09 D6 AE CD 94 0D 7A 2C E1 5E 2D B5 28 F2
28 41 2E F4 42 EB 85 D6 27 C8 24 84 75 16 31 B2
The key agreement value is used as the input to a HKDF key derivation
function with the info parameter master to create the key used to
wrap the base seed:
A7 4D 37 B1 99 00 A8 54 8F 26 18 21 69 0E 51 68
48 82 1E 72 D8 3D AF 0B 83 34 1B 77 72 8F F3 AA
The wrapped base seed is:
30 5D 96 95 BC 08 80 65 A5 41 61 9E BD CC B9 38
6C 8B 9E 7B B5 08 14 2A 1E 80 25 AB 5E B6 B2 5D
E6 6F FC 2E F0 19 35 FA
This information is used to calculate the Recipient information shown
in the example below.
To encrypt a message, we first generate a unique salt value:
7B 10 9B 97 CD 00 0C B9 C1 72 60 61 59 08 15 CE
The base seed and salt value are used to generate the payload
encryption key:
0F 68 C8 90 DE 76 76 03 F0 51 89 82 A3 6E 46 36
C5 47 C5 A0 40 B4 21 9E 25 03 AC 41 80 4D 83 2B
Hallam-Baker Expires 30 December 2023 [Page 38]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Since AES is a block cipher, we also require an initializarion
vector:
B7 9E 72 C4 C3 5A 7D 06 39 CD D4 26 ED 47 62 00
The output sequence is the encrypted bytes:
DD EC C1 C4 B0 49 8D 7A F9 A4 49 88 6E D3 7F AA
9F 7D 77 DF AF 0C 72 8C E1 91 2B AA C2 E6 D9 87
8F 33 1F C8 D3 6C D3 10 76 B8 F7 62 6C 48 09 33
7F C4 82 F6 9E E1 B6 D9 0A 34 5E 42 9D 91 A0 05
Since the message is not signed, there is no need for a trailer. The
completed message is:
{
"DareEnvelope":[{
"enc":"A256CBC",
"kid":"EBQB-FRUM-PRWG-CYFY-BLAO-DUEH-HVPB",
"Salt":"exCbl80ADLnBcmBhWQgVzg",
"recipients":[{
"kid":"MDFQ-C642-7ZJ6-WVCA-QHPW-236B-UNCE",
"epk":{
"PublicKeyECDH":{
"crv":"Ed25519",
"Public":"MMi1LMWpMUvyl0Zu5dxiIwRkgiR1qBtYq3dqEGvxf
AA"}},
"wmk":"UuEt2Y5LpeBxjRuiylqTDNU13yPADoofL_dEeopO_64ZV5jK
oSu2SA"}
]},
"3ezBxLBJjXr5pEmIbtN_qp99d9-vDHKM4ZErqsLm2YePMx_I02zTEHa492Js
SAkzf8SC9p7httkKNF5CnZGgBQ"
]}
13.4. Signed Message
Signed messages specify the digest algorithm to be used in the header
and the signature value in the trailer. Note that the digest
algorithm is not optional since it serves as notice that a decoder
should digest the payload value to enable signature verification.
Hallam-Baker Expires 30 December 2023 [Page 39]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareEnvelope":[{
"dig":"S512"},
"VGhpcyBpcyBhIHRlc3QgbG9uZyBlbm91Z2ggdG8gcmVxdWlyZSBtdWx0aXBs
ZSBibG9ja3M",
{
"signatures":[{
"alg":"S512",
"kid":"MDXM-CKCM-UJTS-LZO3-XAC5-KTVY-DAXA",
"signature":"JZtkvJf0ryob6LC00khVpYlcb56teH-0aoiFjiPWUN
pmm9XbsouoMGFTird0Rx-9fU5Z-bLDXwWN42f5T5yxCw"}
],
"PayloadDigest":"raim8SV5adPbWWn8FMM4mrRAQCO9A2jZ0NZAnFXWlG
0xF6sWGJbnKSdtIJMmMU_hjarlIPEoY3vy9UdVlH5KAg"}
]}
13.5. Signed and Encrypted Message
A signed and encrypted message is encrypted and then signed. The
signer proves knowledge of the payload plaintext by providing the
plaintext witness value.
Hallam-Baker Expires 30 December 2023 [Page 40]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareEnvelope":[{
"enc":"A256CBC",
"dig":"S512",
"kid":"EBQN-4CD5-7ZEE-Y3LB-JC2V-DGXI-A7GO",
"Salt":"z5_5_GsTUvCBBeNgVRDfug",
"recipients":[{
"kid":"MDFQ-C642-7ZJ6-WVCA-QHPW-236B-UNCE",
"epk":{
"PublicKeyECDH":{
"crv":"Ed25519",
"Public":"d-11VbHUe1BBek4pncrK2pn_q9-orDU_zsd6HKyvD
v8"}},
"wmk":"eZO6Ff2jQFrK3PyuUtR8IabKxgZmZRYETS7-ER4c75nFWVes
Ydg2eg"}
]},
"OyhzXMfA1AWzP6TGGU9jeeP0RjzC9aPMTyfJtHneuchxCqgCQoyBTnRSJj5f
58YOfck29dCzK0Owel04c9SnCQ",
{
"signatures":[{
"alg":"S512",
"kid":"MDXM-CKCM-UJTS-LZO3-XAC5-KTVY-DAXA",
"signature":"KeT5fbFM17cdZTvFmf8evf3pR1hrXXxJhqFKQgJ-WP
xV2WxECFlCNZfolYKouUR32SEPGdZtRPRf_KHG0eSGDg",
"witness":"mStCDGih4PHjpfHHofbbtwp84bJulWoa6v6lrp_MjHw"}
],
"PayloadDigest":"PWv7mK6OAoB7OO_Azhj88_ReFX5kbPWxQ3iwH50RPB
H_grVaFi_-78JIs07tV_p6ciJOGHgLV3Z28wuvwV3sxA"}
]}
14. Appendix B: DARE Sequence Examples and Test Vectors
The data payloads in all the following examples are identical, only
the authentication and/or encryption is different.
* Frame 1..n consists of 300 bytes being the byte sequence 00, 01,
02, etc. repeating after 256 bytes.
For conciseness, the raw data format is omitted for examples after
the first, except where the data payload has been transformed, (i.e.
encrypted).
14.1. Simple sequence
The following example shows a simple sequence with first frame and a
single data frame:
Hallam-Baker Expires 30 December 2023 [Page 41]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Since there is no integrity check, there is no need for trailer
entries. The header values are:
Frame 0
{
"DareHeader":{
"policy":{},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"List",
"Index":0}}}
[Empty trailer]
Frame 0
{
"DareHeader":{
"policy":{},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"List",
"Index":0}}}
[Empty trailer]
Frame 1
{
"DareHeader":{
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":1}}}
[Empty trailer]
14.2. Payload and chain digests
The following example shows a chain sequence with a first frame and
three data frames. The headers of these frames is the same as before
but the frames now have trailers specifying the PayloadDigest and
ChainDigest values:
Frame 0
Hallam-Baker Expires 30 December 2023 [Page 42]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareHeader":{
"dig":"S512",
"policy":{},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"Chain",
"Index":0}}}
[Empty trailer]
Frame 0
{
"DareHeader":{
"dig":"S512",
"policy":{},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"Chain",
"Index":0}}}
{
"DareTrailer":{
"PayloadDigest":"z4PhNX7vuL3xVChQ1m2AB9Yg5AULVxXcg_SpIdNs6c5H
0NE8XYXysP-DGNKHfuwvY7kxvUdBeoGlODJ6-SfaPg",
"ChainDigest":"FEHy24Y6cLModDXWH31kVc2a3TdhjXPooKHpLAb2JbsO1Y
QnJolmowXAYHhkOGY0kg3jrKNTjds0myf4Dw1sdg"}}
Frame 1
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":1}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"ChainDigest":"T7S1FcrgY3AaWD4L-t5W1K-3XYkPTcOdGEGyjglTD6yMYV
RVz9tn_KQc6GdA-P4VSRigBygV65OEd2Vv3YDhww"}}
Frame 2
Hallam-Baker Expires 30 December 2023 [Page 43]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":2}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"ChainDigest":"T7S1FcrgY3AaWD4L-t5W1K-3XYkPTcOdGEGyjglTD6yMYV
RVz9tn_KQc6GdA-P4VSRigBygV65OEd2Vv3YDhww"}}
Frame 3
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":3}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"ChainDigest":"T7S1FcrgY3AaWD4L-t5W1K-3XYkPTcOdGEGyjglTD6yMYV
RVz9tn_KQc6GdA-P4VSRigBygV65OEd2Vv3YDhww"}}
14.3. Merkle Tree
The following example shows a chain sequence with a first frame and
six data frames. The trailers now contain the TreePosition and
TreeDigest values:
Frame 0
Hallam-Baker Expires 30 December 2023 [Page 44]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareHeader":{
"dig":"S512",
"policy":{},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"Merkle",
"Index":0}}}
[Empty trailer]
Frame 0
{
"DareHeader":{
"dig":"S512",
"policy":{},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"Merkle",
"Index":0}}}
{
"DareTrailer":{
"PayloadDigest":"z4PhNX7vuL3xVChQ1m2AB9Yg5AULVxXcg_SpIdNs6c5H
0NE8XYXysP-DGNKHfuwvY7kxvUdBeoGlODJ6-SfaPg",
"TreeDigest":"wvk8X5vTHUlVff7cj3k6fHBqXw52PA_7KK5zRLkheMKnGVF
gHY0VL46Fz78rIjCnSNGXmDoBBG5phZRCU1guDA"}}
Frame 1
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":1,
"TreePosition":0}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"TreeDigest":"vJ6ngNATvZcXSMALi5IUqzl1GBxBnTNVcC87VL_BhMRCbAv
KSj8gs0VFgxxLkZ2myrtaDIwhHoswiTiBMLNWug"}}
Hallam-Baker Expires 30 December 2023 [Page 45]
Internet-Draft Mesh: Data At Rest Encryption June 2023
Frame 2
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":2,
"TreePosition":392}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"TreeDigest":"T7S1FcrgY3AaWD4L-t5W1K-3XYkPTcOdGEGyjglTD6yMYVR
Vz9tn_KQc6GdA-P4VSRigBygV65OEd2Vv3YDhww"}}
Frame 3
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":3,
"TreePosition":392}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"TreeDigest":"7fHmkEIsPkN6sDYAOLvpIJn5Dg3PxDDAaq-ll2kh8722kok
kFnZQcYtjuVC71aHNXI18q-lPnfRkmwryG-bhqQ"}}
Frame 4
Hallam-Baker Expires 30 December 2023 [Page 46]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":4,
"TreePosition":1676}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"TreeDigest":"T7S1FcrgY3AaWD4L-t5W1K-3XYkPTcOdGEGyjglTD6yMYVR
Vz9tn_KQc6GdA-P4VSRigBygV65OEd2Vv3YDhww"}}
Frame 5
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":5,
"TreePosition":1676}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"TreeDigest":"vJ6ngNATvZcXSMALi5IUqzl1GBxBnTNVcC87VL_BhMRCbAv
KSj8gs0VFgxxLkZ2myrtaDIwhHoswiTiBMLNWug"}}
Frame 6
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":6,
"TreePosition":2963}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"TreeDigest":"T7S1FcrgY3AaWD4L-t5W1K-3XYkPTcOdGEGyjglTD6yMYVR
Vz9tn_KQc6GdA-P4VSRigBygV65OEd2Vv3YDhww"}}
Hallam-Baker Expires 30 December 2023 [Page 47]
Internet-Draft Mesh: Data At Rest Encryption June 2023
14.4. Signed sequence
The following example shows a tree sequence with a signature in the
final record. The signing key parameters are:
{
"PrivateKeyECDH":{
"Private":"hkYsLO2D7_4vuqZB3MFMV6blEozFJ5KL6CqBtu61Ops",
"crv":"Ed25519"}}
The sequence headers and trailers are:
Frame 0
{
"DareHeader":{
"dig":"S512",
"policy":{},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"Merkle",
"Index":0}}}
[Empty trailer]
Frame 0
{
"DareHeader":{
"dig":"S512",
"policy":{},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"Merkle",
"Index":0}}}
{
"DareTrailer":{
"PayloadDigest":"z4PhNX7vuL3xVChQ1m2AB9Yg5AULVxXcg_SpIdNs6c5H
0NE8XYXysP-DGNKHfuwvY7kxvUdBeoGlODJ6-SfaPg",
"TreeDigest":"wvk8X5vTHUlVff7cj3k6fHBqXw52PA_7KK5zRLkheMKnGVF
gHY0VL46Fz78rIjCnSNGXmDoBBG5phZRCU1guDA"}}
Frame 1
Hallam-Baker Expires 30 December 2023 [Page 48]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":1,
"TreePosition":0}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"TreeDigest":"vJ6ngNATvZcXSMALi5IUqzl1GBxBnTNVcC87VL_BhMRCbAv
KSj8gs0VFgxxLkZ2myrtaDIwhHoswiTiBMLNWug"}}
Frame 2
{
"DareHeader":{
"dig":"S512",
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":2,
"TreePosition":392}}}
{
"DareTrailer":{
"PayloadDigest":"8dyi62d7MDJlsLm6_w4GEgKBjzXBRwppu6qbtmAl6UjZ
DlZeaWQlBsYhOu88-ekpNXpZ2iY96zTRI229zaJ5sw",
"TreeDigest":"T7S1FcrgY3AaWD4L-t5W1K-3XYkPTcOdGEGyjglTD6yMYVR
Vz9tn_KQc6GdA-P4VSRigBygV65OEd2Vv3YDhww"}}
14.5. Encrypted sequence
The following example shows a sequence in which all the frame
payloads are encrypted under the same base seed established in a key
agreement specified in the first frame.
Frame 0
Hallam-Baker Expires 30 December 2023 [Page 49]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareHeader":{
"enc":"A256CBC",
"kid":"EBQJ-FR5L-ZVQZ-RM6Q-NWX7-GWWF-ILA6",
"Salt":"vGDAim2Mp8NzSNukjBII2g",
"recipients":[{
"kid":"MDFQ-C642-7ZJ6-WVCA-QHPW-236B-UNCE",
"epk":{
"PublicKeyECDH":{
"crv":"Ed25519",
"Public":"h-o1arAOJY35KHuhrQ8bKsBmNRfJqfJk-4ayofbIGyM"}},
"wmk":"WqglEont79XuqIaSmsvPqTfi_sk4Iq2UmVDNGLWh_sdxFyARsP
kb7w"}
],
"policy":{
"enc":"none",
"dig":"none",
"EncryptKeys":[{
"PublicKeyECDH":{
"crv":"Ed25519",
"Public":"i3K71T5Wk65mjz0pnIKxja3WkFlrsnDS8fRz1p7sYrI"}}
],
"Sealed":true},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"List",
"Index":0}}}
[Empty trailer]
Frame 0
Hallam-Baker Expires 30 December 2023 [Page 50]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareHeader":{
"enc":"A256CBC",
"kid":"EBQJ-FR5L-ZVQZ-RM6Q-NWX7-GWWF-ILA6",
"Salt":"vGDAim2Mp8NzSNukjBII2g",
"recipients":[{
"kid":"MDFQ-C642-7ZJ6-WVCA-QHPW-236B-UNCE",
"epk":{
"PublicKeyECDH":{
"crv":"Ed25519",
"Public":"h-o1arAOJY35KHuhrQ8bKsBmNRfJqfJk-4ayofbIGyM"}},
"wmk":"WqglEont79XuqIaSmsvPqTfi_sk4Iq2UmVDNGLWh_sdxFyARsP
kb7w"}
],
"policy":{
"enc":"none",
"dig":"none",
"EncryptKeys":[{
"PublicKeyECDH":{
"crv":"Ed25519",
"Public":"i3K71T5Wk65mjz0pnIKxja3WkFlrsnDS8fRz1p7sYrI"}}
],
"Sealed":true},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"List",
"Index":0}}}
[Empty trailer]
Frame 1
Hallam-Baker Expires 30 December 2023 [Page 51]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareHeader":{
"enc":"A256CBC",
"kid":"EBQJ-WIVZ-4VJB-DF5L-2SZB-SGG2-5C2W",
"Salt":"H7FynpxwxNgbJOSlb2PWhg",
"recipients":[{
"kid":"MDFQ-C642-7ZJ6-WVCA-QHPW-236B-UNCE",
"epk":{
"PublicKeyECDH":{
"crv":"Ed25519",
"Public":"vd4lZ3AmmXc3y1dyx1uztncI9sKm9XHD0JWAjADdYV4"}},
"wmk":"1igQ2waotUIIIMfpZ_YcgIQwq0CwETwmXoLaeDvNogGMUu-2GL
KMFA"}
],
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":1}}}
[Empty trailer]
Frame 2
{
"DareHeader":{
"enc":"A256CBC",
"kid":"EBQK-DA4B-GOHA-V6TX-6RNC-TT3Q-CDUR",
"Salt":"i_eTMhLV4Z6_gpmPHm7bow",
"recipients":[{
"kid":"MDFQ-C642-7ZJ6-WVCA-QHPW-236B-UNCE",
"epk":{
"PublicKeyECDH":{
"crv":"Ed25519",
"Public":"_BFmweHRK3_0sjZEZw6A9izpMt88-1KtG60vwPXkjYk"}},
"wmk":"ZiGP-3vKpPW2YbhhMjrK9NJAYGIEwicoykNtIKlJ6q6k2FbTAD
ZrkA"}
],
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":2}}}
[Empty trailer]
Here are the sequence bytes. Note that the content is now encrypted
and has expanded by 25 bytes. These are the salt (16 bytes), the AES
padding (4 bytes) and the JSON-B framing (5 bytes).
Hallam-Baker Expires 30 December 2023 [Page 52]
Internet-Draft Mesh: Data At Rest Encryption June 2023
The following example shows a sequence in which all the frame
payloads are encrypted under separate key agreements specified in the
payload frames.
Frame 0
{
"DareHeader":{
"policy":{
"enc":"none",
"dig":"none",
"Sealed":true},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"List",
"Index":0}}}
[Empty trailer]
Frame 0
{
"DareHeader":{
"policy":{
"enc":"none",
"dig":"none",
"Sealed":true},
"ContentMetaData":"e30",
"SequenceInfo":{
"DataEncoding":"JSON",
"ContainerType":"List",
"Index":0}}}
[Empty trailer]
Frame 1
{
"DareHeader":{
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":1}}}
[Empty trailer]
Frame 2
Hallam-Baker Expires 30 December 2023 [Page 53]
Internet-Draft Mesh: Data At Rest Encryption June 2023
{
"DareHeader":{
"ContentMetaData":"e30",
"SequenceInfo":{
"Index":2}}}
[Empty trailer]
15. Appendix C: Previous Frame Function
public long PreviousFrame (long Frame) {
long x2 = Frame + 1;
long d = 1;
while (x2 > 0) {
if ((x2 & 1) == 1) {
return x2 == 1 ? (d / 2) - 1 : Frame - d;
}
d = d * 2;
x2 = x2 / 2;
}
return 0;
}
16. Appendix D: Outstanding Issues
The following issues need to be addressed.
Hallam-Baker Expires 30 December 2023 [Page 54]
Internet-Draft Mesh: Data At Rest Encryption June 2023
+================+==========================================+
| Issue | Description |
+================+==========================================+
| Signature | No examples are given of signing a |
| | container. Need individual, chain, |
| | tree. Leave notarized for notary draft. |
+----------------+------------------------------------------+
| Indexing | No examples are given of indexing a |
| | container |
+----------------+------------------------------------------+
| Archive | Should include a file archive example |
+----------------+------------------------------------------+
| File Path | Mention the file path security issue in |
| | the security considerations |
+----------------+------------------------------------------+
| Security | Write Security considerations |
| Considerations | |
+----------------+------------------------------------------+
| AES-GCM | Switch to using AES GCM in the examples |
+----------------+------------------------------------------+
| KMAC | Switch to using KMAC for KDF |
+----------------+------------------------------------------+
| Witness | Complete handling of witness values. |
+----------------+------------------------------------------+
| Schema | Complete the schema documentation |
+----------------+------------------------------------------+
Table 1
17. Normative References
[draft-hallambaker-jsonbcd]
Hallam-Baker, P., "Binary Encodings for JavaScript Object
Notation: JSON-B, JSON-C, JSON-D", Work in Progress,
Internet-Draft, draft-hallambaker-jsonbcd-23, 23 October
2022, <https://datatracker.ietf.org/doc/html/draft-
hallambaker-jsonbcd-23>.
[draft-hallambaker-mesh-architecture]
Hallam-Baker, P., "Mathematical Mesh 3.0 Part I:
Architecture Guide", Work in Progress, Internet-Draft,
draft-hallambaker-mesh-architecture-21, 23 October 2022,
<https://datatracker.ietf.org/doc/html/draft-hallambaker-
mesh-architecture-21>.
Hallam-Baker Expires 30 December 2023 [Page 55]
Internet-Draft Mesh: Data At Rest Encryption June 2023
[draft-hallambaker-mesh-security]
Hallam-Baker, P., "Mathematical Mesh 3.0 Part IX Security
Considerations", Work in Progress, Internet-Draft, draft-
hallambaker-mesh-security-09, 20 April 2022,
<https://datatracker.ietf.org/doc/html/draft-hallambaker-
mesh-security-09>.
[draft-hallambaker-mesh-udf]
Hallam-Baker, P., "Mathematical Mesh 3.0 Part II: Uniform
Data Fingerprint.", Work in Progress, Internet-Draft,
draft-hallambaker-mesh-udf-17, 23 October 2022,
<https://datatracker.ietf.org/doc/html/draft-hallambaker-
mesh-udf-17>.
[IANAJOSE] "[Reference Not Found!]".
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC2315] Kaliski, B., "PKCS #7: Cryptographic Message Syntax
Version 1.5", RFC 2315, DOI 10.17487/RFC2315, March 1998,
<https://www.rfc-editor.org/rfc/rfc2315>.
[RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard
(AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,
September 2002, <https://www.rfc-editor.org/rfc/rfc3394>.
[RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R.
Thayer, "OpenPGP Message Format", RFC 4880,
DOI 10.17487/RFC4880, November 2007,
<https://www.rfc-editor.org/rfc/rfc4880>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<https://www.rfc-editor.org/rfc/rfc4949>.
[RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand
Key Derivation Function (HKDF)", RFC 5869,
DOI 10.17487/RFC5869, May 2010,
<https://www.rfc-editor.org/rfc/rfc5869>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/rfc/rfc6838>.
Hallam-Baker Expires 30 December 2023 [Page 56]
Internet-Draft Mesh: Data At Rest Encryption June 2023
[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/rfc/rfc7159>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/rfc/rfc7515>.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<https://www.rfc-editor.org/rfc/rfc7516>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/rfc/rfc7517>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/rfc/rfc7518>.
18. Informative References
[BLOCKCHAIN]
Chain.com, "Blockchain Specification".
[Davis2001]
Davis, D., "Defective Sign & Encrypt in S/MIME, PKCS#7,
MOSS, PEM, PGP, and XML", May 2001.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/rfc/rfc5652>.
[ZIPFILE] PKWARE Inc, "APPNOTE.TXT - .ZIP File Format
Specification", October 2014.
Hallam-Baker Expires 30 December 2023 [Page 57]
