Internet DRAFT - draft-ietf-openpgp-pqc
draft-ietf-openpgp-pqc
Network Working Group S. Kousidis
Internet-Draft BSI
Intended status: Informational J. Roth
Expires: 5 September 2024 F. Strenzke
MTG AG
A. Wussler
Proton AG
4 March 2024
Post-Quantum Cryptography in OpenPGP
draft-ietf-openpgp-pqc-02
Abstract
This document defines a post-quantum public-key algorithm extension
for the OpenPGP protocol. Given the generally assumed threat of a
cryptographically relevant quantum computer, this extension provides
a basis for long-term secure OpenPGP signatures and ciphertexts.
Specifically, it defines composite public-key encryption based on ML-
KEM (formerly CRYSTALS-Kyber), composite public-key signatures based
on ML-DSA (formerly CRYSTALS-Dilithium), both in combination with
elliptic curve cryptography, and SLH-DSA (formerly SPHINCS+) as a
standalone public key signature scheme.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-openpgp-pqc/.
Discussion of this document takes place on the WG Working Group
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Source for this draft and an issue tracker can be found at
https://github.com/openpgp-pqc/draft-openpgp-pqc.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Conventions used in this Document . . . . . . . . . . . . 5
1.1.1. Terminology for Multi-Algorithm Schemes . . . . . . . 5
1.2. Post-Quantum Cryptography . . . . . . . . . . . . . . . . 5
1.2.1. ML-KEM . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.2. ML-DSA . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.3. SLH-DSA . . . . . . . . . . . . . . . . . . . . . . . 6
1.3. Elliptic Curve Cryptography . . . . . . . . . . . . . . . 6
1.3.1. Curve25519 and Curve448 . . . . . . . . . . . . . . . 7
1.3.2. Generic Prime Curves . . . . . . . . . . . . . . . . 7
1.4. Standalone and Multi-Algorithm Schemes . . . . . . . . . 7
1.4.1. Standalone and Composite Multi-Algorithm Schemes . . 7
1.4.2. Non-Composite Algorithm Combinations . . . . . . . . 8
2. Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1. Elliptic curves . . . . . . . . . . . . . . . . . . . . . 8
2.1.1. SEC1 EC Point Wire Format . . . . . . . . . . . . . . 8
2.1.2. Measures to Ensure Secure Implementations . . . . . . 8
3. Supported Public Key Algorithms . . . . . . . . . . . . . . . 9
3.1. Algorithm Specifications . . . . . . . . . . . . . . . . 9
3.1.1. Experimental Codepoints for Interop Testing . . . . . 10
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3.2. Parameter Specification . . . . . . . . . . . . . . . . . 10
3.2.1. SLH-DSA-SHA2 . . . . . . . . . . . . . . . . . . . . 11
3.2.2. SLH-DSA-SHAKE . . . . . . . . . . . . . . . . . . . . 11
4. Algorithm Combinations . . . . . . . . . . . . . . . . . . . 12
4.1. Composite KEMs . . . . . . . . . . . . . . . . . . . . . 12
4.2. Parallel Public-Key Encryption . . . . . . . . . . . . . 12
4.3. Composite Signatures . . . . . . . . . . . . . . . . . . 12
4.4. Multiple Signatures . . . . . . . . . . . . . . . . . . . 13
5. Composite KEM schemes . . . . . . . . . . . . . . . . . . . . 13
5.1. Building Blocks . . . . . . . . . . . . . . . . . . . . . 13
5.1.1. ECC-Based KEMs . . . . . . . . . . . . . . . . . . . 13
5.1.2. ML-KEM . . . . . . . . . . . . . . . . . . . . . . . 18
5.2. Composite Encryption Schemes with ML-KEM . . . . . . . . 19
5.2.1. Fixed information . . . . . . . . . . . . . . . . . . 21
5.2.2. Key combiner . . . . . . . . . . . . . . . . . . . . 21
5.2.3. Key generation procedure . . . . . . . . . . . . . . 22
5.2.4. Encryption procedure . . . . . . . . . . . . . . . . 22
5.2.5. Decryption procedure . . . . . . . . . . . . . . . . 23
5.3. Packet specifications . . . . . . . . . . . . . . . . . . 24
5.3.1. Public-Key Encrypted Session Key Packets (Tag 1) . . 24
5.3.2. Key Material Packets . . . . . . . . . . . . . . . . 25
6. Composite Signature Schemes . . . . . . . . . . . . . . . . . 25
6.1. Building blocks . . . . . . . . . . . . . . . . . . . . . 25
6.1.1. EdDSA-Based signatures . . . . . . . . . . . . . . . 25
6.1.2. ECDSA-Based signatures . . . . . . . . . . . . . . . 26
6.1.3. ML-DSA signatures . . . . . . . . . . . . . . . . . . 27
6.2. Composite Signature Schemes with ML-DSA . . . . . . . . . 28
6.2.1. Signature data digest . . . . . . . . . . . . . . . . 28
6.2.2. Key generation procedure . . . . . . . . . . . . . . 28
6.2.3. Signature Generation . . . . . . . . . . . . . . . . 29
6.2.4. Signature Verification . . . . . . . . . . . . . . . 29
6.3. Packet Specifications . . . . . . . . . . . . . . . . . . 30
6.3.1. Signature Packet (Tag 2) . . . . . . . . . . . . . . 30
6.3.2. Key Material Packets . . . . . . . . . . . . . . . . 30
7. SLH-DSA . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
7.1. The SLH-DSA Algorithms . . . . . . . . . . . . . . . . . 31
7.1.1. Signature Data Digest . . . . . . . . . . . . . . . . 32
7.1.2. Key generation . . . . . . . . . . . . . . . . . . . 33
7.1.3. Signature Generation . . . . . . . . . . . . . . . . 33
7.1.4. Signature Verification . . . . . . . . . . . . . . . 33
7.2. Packet specifications . . . . . . . . . . . . . . . . . . 33
7.2.1. Signature Packet (Tag 2) . . . . . . . . . . . . . . 33
7.2.2. Key Material Packets . . . . . . . . . . . . . . . . 33
8. Notes on Algorithms . . . . . . . . . . . . . . . . . . . . . 34
8.1. Symmetric Algorithms for SEIPD Packets . . . . . . . . . 34
9. Migration Considerations . . . . . . . . . . . . . . . . . . 34
9.1. Key preference . . . . . . . . . . . . . . . . . . . . . 35
9.2. Key generation strategies . . . . . . . . . . . . . . . . 35
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10. Security Considerations . . . . . . . . . . . . . . . . . . . 36
10.1. Security Aspects of Composite Signatures . . . . . . . . 36
10.2. Hashing in ECC-KEM . . . . . . . . . . . . . . . . . . . 36
10.3. Key combiner . . . . . . . . . . . . . . . . . . . . . . 37
10.4. Domain separation and binding . . . . . . . . . . . . . 37
10.5. SLH-DSA Message Randomizer . . . . . . . . . . . . . . . 39
10.6. Binding hashes in signatures with signature
algorithms . . . . . . . . . . . . . . . . . . . . . . . 39
10.7. Symmetric Algorithms for SEIPD Packets . . . . . . . . . 39
11. Additional considerations . . . . . . . . . . . . . . . . . . 39
11.1. Performance Considerations for SLH-DSA . . . . . . . . . 39
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
13. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 42
13.1. draft-wussler-openpgp-pqc-01 . . . . . . . . . . . . . . 43
13.2. draft-wussler-openpgp-pqc-02 . . . . . . . . . . . . . . 43
13.3. draft-wussler-openpgp-pqc-03 . . . . . . . . . . . . . . 43
13.4. draft-wussler-openpgp-pqc-04 . . . . . . . . . . . . . . 43
13.5. draft-ietf-openpgp-pqc-00 . . . . . . . . . . . . . . . 43
13.6. draft-ietf-openpgp-pqc-01 . . . . . . . . . . . . . . . 44
13.7. draft-ietf-openpgp-pqc-02 . . . . . . . . . . . . . . . 44
14. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 44
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 44
15.1. Normative References . . . . . . . . . . . . . . . . . . 44
15.2. Informative References . . . . . . . . . . . . . . . . . 45
Appendix A. Test Vectors . . . . . . . . . . . . . . . . . . . . 47
A.1. Sample v6 PQC Subkey Artifacts . . . . . . . . . . . . . 47
A.2. V4 PQC Subkey Artifacts . . . . . . . . . . . . . . . . . 51
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 57
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 58
1. Introduction
The OpenPGP protocol supports various traditional public-key
algorithms based on the factoring or discrete logarithm problem. As
the security of algorithms based on these mathematical problems is
endangered by the advent of quantum computers, there is a need to
extend OpenPGP by algorithms that remain secure in the presence of
quantum computers.
Such cryptographic algorithms are referred to as post-quantum
cryptography. The algorithms defined in this extension were chosen
for standardization by the National Institute of Standards and
Technology (NIST) in mid 2022 [NISTIR-8413] as the result of the NIST
Post-Quantum Cryptography Standardization process initiated in 2016
[NIST-PQC]. Namely, these are ML-KEM [FIPS-203] as a Key
Encapsulation Mechanism (KEM), a KEM being a modern building block
for public-key encryption, and ML-DSA [FIPS-204] as well as SLH-DSA
[FIPS-205] as signature schemes.
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For the two ML-* schemes, this document follows the conservative
strategy to deploy post-quantum in combination with traditional
schemes such that the security is retained even if all schemes but
one in the combination are broken. In contrast, the stateless hash-
based signature scheme SLH-DSA is considered to be sufficiently well
understood with respect to its security assumptions in order to be
used standalone. To this end, this document specifies the following
new set: SLH-DSA standalone and the two ML-* as composite with ECC-
based KEM and digital signature schemes. Here, the term "composite"
indicates that any data structure or algorithm pertaining to the
combination of the two components appears as single data structure or
algorithm from the protocol perspective.
The document specifies the conventions for interoperability between
compliant OpenPGP implementations that make use of this extension and
the newly defined algorithms or algorithm combinations.
1.1. Conventions used in this Document
1.1.1. Terminology for Multi-Algorithm Schemes
The terminology in this document is oriented towards the definitions
in [draft-driscoll-pqt-hybrid-terminology]. Specifically, the terms
"multi-algorithm", "composite" and "non-composite" are used in
correspondence with the definitions therein. The abbreviation "PQ"
is used for post-quantum schemes. To denote the combination of post-
quantum and traditional schemes, the abbreviation "PQ/T" is used.
The short form "PQ(/T)" stands for PQ or PQ/T.
1.2. Post-Quantum Cryptography
This section describes the individual post-quantum cryptographic
schemes. All schemes listed here are believed to provide security in
the presence of a cryptographically relevant quantum computer.
However, the mathematical problems on which the two ML-* schemes and
SLH-DSA are based, are fundamentally different, and accordingly the
level of trust commonly placed in them as well as their performance
characteristics vary.
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[Note to the reader: This specification refers to the NIST PQC draft
standards FIPS 203, FIPS 204, and FIPS 205 as if they were a final
specification. This is a temporary solution until the final versions
of these documents are available. The goal is to provide a
sufficiently precise specification of the algorithms already at the
draft stage of this specification, so that it is possible for
implementers to create interoperable implementations. Furthermore,
we want to point out that, depending on possible future changes to
the draft standards by NIST, this specification may be updated as
soon as corresponding information becomes available.]
1.2.1. ML-KEM
ML-KEM [FIPS-203] is based on the hardness of solving the learning-
with-errors problem in module lattices (MLWE). The scheme is
believed to provide security against cryptanalytic attacks by
classical as well as quantum computers. This specification defines
ML-KEM only in composite combination with ECC-based encryption
schemes in order to provide a pre-quantum security fallback.
1.2.2. ML-DSA
ML-DSA [FIPS-204] is a signature scheme that, like ML-KEM, is based
on the hardness of solving the Learning With Errors problem and a
variant of the Short Integer Solution problem in module lattices
(MLWE and SelfTargetMSIS). Accordingly, this specification only
defines ML-DSA in composite combination with ECC-based signature
schemes.
1.2.3. SLH-DSA
SLH-DSA [FIPS-205] is a stateless hash-based signature scheme. Its
security relies on the hardness of finding preimages for
cryptographic hash functions. This feature is generally considered
to be a high security guarantee. Therefore, this specification
defines SLH-DSA as a standalone signature scheme.
In deployments the performance characteristics of SLH-DSA should be
taken into account. We refer to Section 11.1 for a discussion of the
performance characteristics of this scheme.
1.3. Elliptic Curve Cryptography
The ECC-based encryption is defined here as a KEM. This is in
contrast to [I-D.ietf-openpgp-crypto-refresh] where the ECC-based
encryption is defined as a public-key encryption scheme.
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All elliptic curves for the use in the composite combinations are
taken from [I-D.ietf-openpgp-crypto-refresh]. However, as explained
in the following, in the case of Curve25519 encoding changes are
applied to the new composite schemes.
1.3.1. Curve25519 and Curve448
Curve25519 and Curve448 are defined in [RFC7748] for use in a Diffie-
Hellman key agreement scheme and defined in [RFC8032] for use in a
digital signature scheme. For Curve25519 this specification adopts
the encoding of objects as defined in [RFC7748].
1.3.2. Generic Prime Curves
For interoperability this extension offers CRYSTALS-* in composite
combinations with the NIST curves P-256, P-384 defined in [SP800-186]
and the Brainpool curves brainpoolP256r1, brainpoolP384r1 defined in
[RFC5639].
1.4. Standalone and Multi-Algorithm Schemes
This section provides a categorization of the new algorithms and
their combinations.
1.4.1. Standalone and Composite Multi-Algorithm Schemes
This specification introduces new cryptographic schemes, which can be
categorized as follows:
* PQ/T multi-algorithm public-key encryption, namely a composite
combination of ML-KEM with an ECC-based KEM,
* PQ/T multi-algorithm digital signature, namely composite
combinations of ML-DSA with ECC-based signature schemes,
* PQ digital signature, namely SLH-DSA as a standalone cryptographic
algorithm.
For each of the composite schemes, this specification mandates that
the recipient has to successfully perform the cryptographic
algorithms for each of the component schemes used in a cryptographic
message, in order for the message to be deciphered and considered as
valid. This means that all component signatures must be verified
successfully in order to achieve a successful verification of the
composite signature. In the case of the composite public-key
decryption, each of the component KEM decapsulation operations must
succeed.
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1.4.2. Non-Composite Algorithm Combinations
As the OpenPGP protocol [I-D.ietf-openpgp-crypto-refresh] allows for
multiple signatures to be applied to a single message, it is also
possible to realize non-composite combinations of signatures.
Furthermore, multiple OpenPGP signatures may be combined on the
application layer. These latter two cases realize non-composite
combinations of signatures. Section 4.4 specifies how
implementations should handle the verification of such combinations
of signatures.
Furthermore, the OpenPGP protocol also allows for parallel encryption
to different keys held by the same recipient. Accordingly, if the
sender makes use of this feature and sends an encrypted message with
multiple PKESK packages for different encryption keys held by the
same recipient, a non-composite multi-algorithm public-key encryption
is realized where the recipient has to decrypt only one of the PKESK
packages in order to decrypt the message. See Section 4.2 for
restrictions on parallel encryption mandated by this specification.
2. Preliminaries
This section provides some preliminaries for the definitions in the
subsequent sections.
2.1. Elliptic curves
2.1.1. SEC1 EC Point Wire Format
Elliptic curve points of the generic prime curves are encoded using
the SEC1 (uncompressed) format as the following octet string:
B = 04 || X || Y
where X and Y are coordinates of the elliptic curve point P = (X, Y),
and each coordinate is encoded in the big-endian format and zero-
padded to the adjusted underlying field size. The adjusted
underlying field size is the underlying field size rounded up to the
nearest 8-bit boundary, as noted in the "Field size" column in
Table 6, Table 7, or Table 11. This encoding is compatible with the
definition given in [SEC1].
2.1.2. Measures to Ensure Secure Implementations
In the following measures are described that ensure secure
implementations according to existing best practices and standards
defining the operations of Elliptic Curve Cryptography.
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Even though the zero point, also called the point at infinity, may
occur as a result of arithmetic operations on points of an elliptic
curve, it MUST NOT appear in any ECC data structure defined in this
document.
Furthermore, when performing the explicitly listed operations in
Section 5.1.1.1, Section 5.1.1.2 or Section 5.1.1.3 it is REQUIRED to
follow the specification and security advisory mandated from the
respective elliptic curve specification.
3. Supported Public Key Algorithms
This section specifies the composite ML-KEM + ECC and ML-DSA + ECC
schemes as well as the standalone SLH-DSA signature scheme. The
composite schemes are fully specified via their algorithm ID. The
SLH-DSA signature schemes are fully specified by their algorithm ID
and an additional parameter ID.
3.1. Algorithm Specifications
For encryption, the following composite KEM schemes are specified:
+==============+======================+=============+============+
| ID | Algorithm | Requirement | Definition |
+==============+======================+=============+============+
| TBD (105 for | ML-KEM-768 + X25519 | MUST | Section |
| testing) | | | 5.2 |
+--------------+----------------------+-------------+------------+
| TBD (106 for | ML-KEM-1024 + X448 | SHOULD | Section |
| testing) | | | 5.2 |
+--------------+----------------------+-------------+------------+
| TBD | ML-KEM-768 + ECDH- | MAY | Section |
| | NIST-P-256 | | 5.2 |
+--------------+----------------------+-------------+------------+
| TBD | ML-KEM-1024 + ECDH- | MAY | Section |
| | NIST-P-384 | | 5.2 |
+--------------+----------------------+-------------+------------+
| TBD | ML-KEM-768 + ECDH- | MAY | Section |
| | brainpoolP256r1 | | 5.2 |
+--------------+----------------------+-------------+------------+
| TBD | ML-KEM-1024 + ECDH- | MAY | Section |
| | brainpoolP384r1 | | 5.2 |
+--------------+----------------------+-------------+------------+
Table 1: KEM algorithm specifications
For signatures, the following (composite) signature schemes are
specified:
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+==============+=======================+=============+============+
| ID | Algorithm | Requirement | Definition |
+==============+=======================+=============+============+
| TBD (107 for | ML-DSA-65 + Ed25519 | MUST | Section |
| testing) | | | 6.2 |
+--------------+-----------------------+-------------+------------+
| TBD (108 for | ML-DSA-87 + Ed448 | SHOULD | Section |
| testing) | | | 6.2 |
+--------------+-----------------------+-------------+------------+
| TBD | ML-DSA-65 + ECDSA- | MAY | Section |
| | NIST-P-256 | | 6.2 |
+--------------+-----------------------+-------------+------------+
| TBD | ML-DSA-87 + ECDSA- | MAY | Section |
| | NIST-P-384 | | 6.2 |
+--------------+-----------------------+-------------+------------+
| TBD | ML-DSA-65 + ECDSA- | MAY | Section |
| | brainpoolP256r1 | | 6.2 |
+--------------+-----------------------+-------------+------------+
| TBD | ML-DSA-87 + ECDSA- | MAY | Section |
| | brainpoolP384r1 | | 6.2 |
+--------------+-----------------------+-------------+------------+
| TBD (109 for | SLH-DSA-SHA2 | SHOULD | Section |
| testing) | | | 7.1 |
+--------------+-----------------------+-------------+------------+
| TBD | SLH-DSA-SHAKE | MAY | Section |
| | | | 7.1 |
+--------------+-----------------------+-------------+------------+
Table 2: Signature algorithm specifications
3.1.1. Experimental Codepoints for Interop Testing
[ Note: this section to be removed before publication ]
Algorithms indicated as MAY are not assigned a codepoint in the
current state of the draft since there are not enough private/
experimental code points available to cover all newly introduced
public-key algorithm identifiers.
The use of private/experimental codepoints during development are
intended to be used in non-released software only, for
experimentation and interop testing purposes only. An OpenPGP
implementation MUST NOT produce a formal release using these
experimental codepoints. This draft will not be sent to IANA without
every listed algorithm having a non-experimental codepoint.
3.2. Parameter Specification
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3.2.1. SLH-DSA-SHA2
For the SLH-DSA-SHA2 signature algorithm from Table 2, the following
parameters are specified:
+==============+===================+
| Parameter ID | Parameter |
+==============+===================+
| 1 | SLH-DSA-SHA2-128s |
+--------------+-------------------+
| 2 | SLH-DSA-SHA2-128f |
+--------------+-------------------+
| 3 | SLH-DSA-SHA2-192s |
+--------------+-------------------+
| 4 | SLH-DSA-SHA2-192f |
+--------------+-------------------+
| 5 | SLH-DSA-SHA2-256s |
+--------------+-------------------+
| 6 | SLH-DSA-SHA2-256f |
+--------------+-------------------+
Table 3: SLH-DSA-SHA2 security
parameters
All security parameters inherit the requirement of SLH-DSA-SHA2 from
Table 2. That is, implementations SHOULD implement the parameters
specified in Table 3. The values 0x00 and 0xFF are reserved for
future extensions.
3.2.2. SLH-DSA-SHAKE
For the SLH-DSA-SHAKE signature algorithm from Table 2, the following
parameters are specified:
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+==============+====================+
| Parameter ID | Parameter |
+==============+====================+
| 1 | SLH-DSA-SHAKE-128s |
+--------------+--------------------+
| 2 | SLH-DSA-SHAKE-128f |
+--------------+--------------------+
| 3 | SLH-DSA-SHAKE-192s |
+--------------+--------------------+
| 4 | SLH-DSA-SHAKE-192f |
+--------------+--------------------+
| 5 | SLH-DSA-SHAKE-256s |
+--------------+--------------------+
| 6 | SLH-DSA-SHAKE-256f |
+--------------+--------------------+
Table 4: SLH-DSA-SHAKE security
parameters
All security parameters inherit the requirement of SLH-DSA-SHAKE from
Table 2. That is, implementations MAY implement the parameters
specified in Table 4. The values 0x00 and 0xFF are reserved for
future extensions.
4. Algorithm Combinations
4.1. Composite KEMs
The ML-KEM + ECC public-key encryption involves both the ML-KEM and
an ECC-based KEM in an a priori non-separable manner. This is
achieved via KEM combination, i.e. both key encapsulations/
decapsulations are performed in parallel, and the resulting key
shares are fed into a key combiner to produce a single shared secret
for message encryption.
4.2. Parallel Public-Key Encryption
As explained in Section 1.4.2, the OpenPGP protocol inherently
supports parallel encryption to different keys of the same recipient.
Implementations MUST NOT encrypt a message with a purely traditional
public-key encryption key of a recipient if it is encrypted with a
PQ/T key of the same recipient.
4.3. Composite Signatures
The ML-DSA + ECC signature consists of independent ML-DSA and ECC
signatures, and an implementation MUST successfully validate both
signatures to state that the ML-DSA + ECC signature is valid.
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4.4. Multiple Signatures
The OpenPGP message format allows multiple signatures of a message,
i.e. the attachment of multiple signature packets.
An implementation MAY sign a message with a traditional key and a
PQ(/T) key from the same sender. This ensures backwards
compatibility due to [I-D.ietf-openpgp-crypto-refresh] Section 5.2.5,
since a legacy implementation without PQ(/T) support can fall back on
the traditional signature.
Newer implementations with PQ(/T) support MAY ignore the traditional
signature(s) during validation.
Implementations SHOULD consider the message correctly signed if at
least one of the non-ignored signatures validates successfully.
[Note to the reader: The last requirement, that one valid signature
is sufficient to identify a message as correctly signed, is an
interpretation of [I-D.ietf-openpgp-crypto-refresh] Section 5.2.5.]
5. Composite KEM schemes
5.1. Building Blocks
5.1.1. ECC-Based KEMs
In this section we define the encryption, decryption, and data
formats for the ECDH component of the composite algorithms.
Table 5, Table 6, and Table 7 describe the ECC-KEM parameters and
artifact lengths. The artifacts in Table 5 follow the encodings
described in [RFC7748].
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+========================+=======================+==================+
| | X25519 | X448 |
+========================+=======================+==================+
| Algorithm ID reference | TBD (105 for | TBD (106 for |
| | testing) | testing) |
+------------------------+-----------------------+------------------+
| Field size | 32 octets | 56 octets |
+------------------------+-----------------------+------------------+
| ECC-KEM | x25519Kem | x448Kem (Section |
| | (Section 5.1.1.1) | 5.1.1.2) |
+------------------------+-----------------------+------------------+
| ECDH public key | 32 octets | 56 octets |
| | [RFC7748] | [RFC7748] |
+------------------------+-----------------------+------------------+
| ECDH secret key | 32 octets | 56 octets |
| | [RFC7748] | [RFC7748] |
+------------------------+-----------------------+------------------+
| ECDH ephemeral | 32 octets | 56 octets |
| | [RFC7748] | [RFC7748] |
+------------------------+-----------------------+------------------+
| ECDH share | 32 octets | 56 octets |
| | [RFC7748] | [RFC7748] |
+------------------------+-----------------------+------------------+
| Key share | 32 octets | 64 octets |
+------------------------+-----------------------+------------------+
| Hash | SHA3-256 | SHA3-512 |
+------------------------+-----------------------+------------------+
Table 5: Montgomery curves parameters and artifact lengths
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+==============+===========================+====================+
| | NIST P-256 | NIST P-384 |
+==============+===========================+====================+
| Algorithm ID | TBD (ML-KEM-768 + ECDH- | TBD (ML-KEM-1024 + |
| reference | NIST-P-256) | ECDH-NIST-P-384) |
+--------------+---------------------------+--------------------+
| Field size | 32 octets | 48 octets |
+--------------+---------------------------+--------------------+
| ECC-KEM | ecdhKem (Section 5.1.1.3) | ecdhKem |
| | | (Section 5.1.1.3) |
+--------------+---------------------------+--------------------+
| ECDH public | 65 octets of SEC1-encoded | 97 octets of |
| key | public point | SEC1-encoded |
| | | public point |
+--------------+---------------------------+--------------------+
| ECDH secret | 32 octets big-endian | 48 octets big- |
| key | encoded secret scalar | endian encoded |
| | | secret scalar |
+--------------+---------------------------+--------------------+
| ECDH | 65 octets of SEC1-encoded | 97 octets of |
| ephemeral | ephemeral point | SEC1-encoded |
| | | ephemeral point |
+--------------+---------------------------+--------------------+
| ECDH share | 65 octets of SEC1-encoded | 97 octets of |
| | shared point | SEC1-encoded |
| | | shared point |
+--------------+---------------------------+--------------------+
| Key share | 32 octets | 64 octets |
+--------------+---------------------------+--------------------+
| Hash | SHA3-256 | SHA3-512 |
+--------------+---------------------------+--------------------+
Table 6: NIST curves parameters and artifact lengths
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+==============+===========================+=======================+
| | brainpoolP256r1 | brainpoolP384r1 |
+==============+===========================+=======================+
| Algorithm ID | TBD (ML-KEM-768 + ECDH- | TBD (ML-KEM-1024 + |
| reference | brainpoolP256r1) | ECDH-brainpoolP384r1) |
+--------------+---------------------------+-----------------------+
| Field size | 32 octets | 48 octets |
+--------------+---------------------------+-----------------------+
| ECC-KEM | ecdhKem (Section 5.1.1.3) | ecdhKem |
| | | (Section 5.1.1.3) |
+--------------+---------------------------+-----------------------+
| ECDH public | 65 octets of SEC1-encoded | 97 octets of |
| key | public point | SEC1-encoded public |
| | | point |
+--------------+---------------------------+-----------------------+
| ECDH secret | 32 octets big-endian | 48 octets big-endian |
| key | encoded secret scalar | encoded secret scalar |
+--------------+---------------------------+-----------------------+
| ECDH | 65 octets of SEC1-encoded | 97 octets of |
| ephemeral | ephemeral point | SEC1-encoded |
| | | ephemeral point |
+--------------+---------------------------+-----------------------+
| ECDH share | 65 octets of SEC1-encoded | 97 octets of |
| | shared point | SEC1-encoded shared |
| | | point |
+--------------+---------------------------+-----------------------+
| Key share | 32 octets | 64 octets |
+--------------+---------------------------+-----------------------+
| Hash | SHA3-256 | SHA3-512 |
+--------------+---------------------------+-----------------------+
Table 7: Brainpool curves parameters and artifact lengths
The SEC1 format for point encoding is defined in Section 2.1.1.
The various procedures to perform the operations of an ECC-based KEM
are defined in the following subsections. Specifically, each of
these subsections defines the instances of the following operations:
(eccCipherText, eccKeyShare) <- ECC-KEM.Encaps(eccPublicKey)
and
(eccKeyShare) <- ECC-KEM.Decaps(eccSecretKey, eccCipherText, eccPublicKey)
To instantiate ECC-KEM, one must select a parameter set from Table 5,
Table 6, or Table 7.
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5.1.1.1. X25519-KEM
The encapsulation and decapsulation operations of x25519kem are
described using the function X25519() and encodings defined in
[RFC7748]. The eccSecretKey is denoted as r, the eccPublicKey as R,
they are subject to the equation R = X25519(r, U(P)). Here, U(P)
denotes the u-coordinate of the base point of Curve25519.
The operation x25519Kem.Encaps() is defined as follows:
1. Generate an ephemeral key pair {v, V} via V = X25519(v,U(P))
where v is a randomly generated octet string with a length of 32
octets
2. Compute the shared coordinate X = X25519(v, R) where R is the
recipient's public key eccPublicKey
3. Set the output eccCipherText to V
4. Set the output eccKeyShare to SHA3-256(X || eccCipherText ||
eccPublicKey)
The operation x25519Kem.Decaps() is defined as follows:
1. Compute the shared coordinate X = X25519(r, V), where r is the
eccSecretKey and V is the eccCipherText
2. Set the output eccKeyShare to SHA3-256(X || eccCipherText ||
eccPublicKey)
5.1.1.2. X448-KEM
The encapsulation and decapsulation operations of x448kem are
described using the function X448() and encodings defined in
[RFC7748]. The eccSecretKey is denoted as r, the eccPublicKey as R,
they are subject to the equation R = X25519(r, U(P)). Here, U(P)
denotes the u-coordinate of the base point of Curve448.
The operation x448.Encaps() is defined as follows:
1. Generate an ephemeral key pair {v, V} via V = X448(v,U(P)) where
v is a randomly generated octet string with a length of 56 octets
2. Compute the shared coordinate X = X448(v, R) where R is the
recipient's public key eccPublicKey
3. Set the output eccCipherText to V
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4. Set the output eccKeyShare to SHA3-512(X || eccCipherText ||
eccPublicKey)
The operation x448Kem.Decaps() is defined as follows:
1. Compute the shared coordinate X = X448(r, V), where r is the
eccSecretKey and V is the eccCipherText
2. Set the output eccKeyShare to SHA3-512(X || eccCipherText ||
eccPublicKey)
5.1.1.3. ECDH-KEM
The operation ecdhKem.Encaps() is defined as follows:
1. Generate an ephemeral key pair {v, V=vG} as defined in
[SP800-186] or [RFC5639] where v is a random scalar with 0 < v <
n, n being the base point order of the elliptic curve domain
parameters
2. Compute the shared point S = vR, where R is the component public
key eccPublicKey, according to [SP800-186] or [RFC5639]
3. Extract the X coordinate from the SEC1 encoded point S = 04 ||
X || Y as defined in section Section 2.1.1
4. Set the output eccCipherText to the SEC1 encoding of V
5. Set the output eccKeyShare to Hash(X || eccCipherText ||
eccPublicKey), with Hash chosen according to Table 6 or Table 7
The operation ecdhKem.Decaps() is defined as follows:
1. Compute the shared Point S as rV, where r is the eccSecretKey and
V is the eccCipherText, according to [SP800-186] or [RFC5639]
2. Extract the X coordinate from the SEC1 encoded point S = 04 ||
X || Y as defined in section Section 2.1.1
3. Set the output eccKeyShare to Hash(X || eccCipherText ||
eccPublicKey), with Hash chosen according to Table 6 or Table 7
5.1.2. ML-KEM
ML-KEM features the following operations:
(mlkemCipherText, mlkemKeyShare) <- ML-KEM.Encaps(mlkemPublicKey)
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and
(mlkemKeyShare) <- ML-KEM.Decaps(mlkemCipherText, mlkemSecretKey)
The above are the operations ML-KEM.Encaps and ML-KEM.Decaps defined
in [FIPS-203]. Note that mlkemPublicKey is the encapsulation and
mlkemSecretKey is the decapsulation key.
ML-KEM has the parametrization with the corresponding artifact
lengths in octets as given in Table 8. All artifacts are encoded as
defined in [FIPS-203].
+==============+=============+========+========+============+=======+
| Algorithm | ML-KEM | Public | Secret | Ciphertext | Key |
| ID | | key | key | | share |
| reference | | | | | |
+==============+=============+========+========+============+=======+
| TBD | ML-KEM-768 | 1184 | 2400 | 1088 | 32 |
+--------------+-------------+--------+--------+------------+-------+
| TBD | ML-KEM-1024 | 1568 | 3168 | 1568 | 32 |
+--------------+-------------+--------+--------+------------+-------+
Table 8: ML-KEM parameters artifact lengths in octets
To instantiate ML-KEM, one must select a parameter set from the
column "ML-KEM" of Table 8.
The procedure to perform ML-KEM.Encaps() is as follows:
1. Invoke (mlkemCipherText, mlkemKeyShare) <- ML-
KEM.Encaps(mlkemPublicKey), where mlkemPublicKey is the
recipient's public key
2. Set mlkemCipherText as the ML-KEM ciphertext
3. Set mlkemKeyShare as the ML-KEM symmetric key share
The procedure to perform ML-KEM.Decaps() is as follows:
1. Invoke mlkemKeyShare <- ML-KEM.Decaps(mlkemCipherText,
mlkemSecretKey)
2. Set mlkemKeyShare as the ML-KEM symmetric key share
5.2. Composite Encryption Schemes with ML-KEM
Table 1 specifies the following ML-KEM + ECC composite public-key
encryption schemes:
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+========================+=============+=========+=================+
| Algorithm ID reference | ML-KEM |ECC-KEM | ECC-KEM curve |
+========================+=============+=========+=================+
| TBD (105 for testing) | ML-KEM-768 |x25519Kem| Curve25519 |
+------------------------+-------------+---------+-----------------+
| TBD (106 for testing) | ML-KEM-1024 |x448Kem | Curve448 |
+------------------------+-------------+---------+-----------------+
| TBD (ML-KEM-768 + | ML-KEM-768 |ecdhKem | NIST P-256 |
| ECDH-NIST-P-256) | | | |
+------------------------+-------------+---------+-----------------+
| TBD (ML-KEM-1024 + | ML-KEM-1024 |ecdhKem | NIST P-384 |
| ECDH-NIST-P-384) | | | |
+------------------------+-------------+---------+-----------------+
| TBD (ML-KEM-768 + | ML-KEM-768 |ecdhKem | brainpoolP256r1 |
| ECDH-brainpoolP256r1) | | | |
+------------------------+-------------+---------+-----------------+
| TBD (ML-KEM-1024 + | ML-KEM-1024 |ecdhKem | brainpoolP384r1 |
| ECDH-brainpoolP384r1) | | | |
+------------------------+-------------+---------+-----------------+
Table 9: ML-KEM + ECC composite schemes
The ML-KEM + ECC composite public-key encryption schemes are built
according to the following principal design:
* The ML-KEM encapsulation algorithm is invoked to create a ML-KEM
ciphertext together with a ML-KEM symmetric key share.
* The encapsulation algorithm of an ECC-based KEM, namely one out of
X25519-KEM, X448-KEM, or ECDH-KEM is invoked to create an ECC
ciphertext together with an ECC symmetric key share.
* A Key-Encryption-Key (KEK) is computed as the output of a key
combiner that receives as input both of the above created
symmetric key shares and the protocol binding information.
* The session key for content encryption is then wrapped as
described in [RFC3394] using AES-256 as algorithm and the KEK as
key.
* The PKESK package's algorithm-specific parts are made up of the
ML-KEM ciphertext, the ECC ciphertext, and the wrapped session
key.
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5.2.1. Fixed information
For the composite KEM schemes defined in Table 1 the following
procedure, justified in Section 10.4, MUST be used to derive a string
to use as binding between the KEK and the communication parties.
// Input:
// algID - the algorithm ID encoded as octet
fixedInfo = algID
5.2.2. Key combiner
For the composite KEM schemes defined in Table 1 the following
procedure MUST be used to compute the KEK that wraps a session key.
The construction is a one-step key derivation function compliant to
[SP800-56C] Section 4, based on KMAC256 [SP800-185]. It is given by
the following algorithm, which computes the key encryption key KEK
that is used to wrap, i.e., encrypt, the session key.
// multiKeyCombine(eccKeyShare, eccCipherText,
// mlkemKeyShare, mlkemCipherText,
// fixedInfo, oBits)
//
// Input:
// eccKeyShare - the ECC key share encoded as an octet string
// eccCipherText - the ECC ciphertext encoded as an octet string
// mlkemKeyShare - the ML-KEM key share encoded as an octet string
// mlkemCipherText - the ML-KEM ciphertext encoded as an octet string
// fixedInfo - the fixed information octet string
// oBits - the size of the output keying material in bits
//
// Constants:
// domSeparation - the UTF-8 encoding of the string
// "OpenPGPCompositeKeyDerivationFunction"
// counter - the 4 byte value 00 00 00 01
// customizationString - the UTF-8 encoding of the string "KDF"
eccData = eccKeyShare || eccCipherText
mlkemData = mlkemKeyShare || mlkemCipherText
encData = counter || eccData || mlkemData || fixedInfo
KEK = KMAC256(domSeparation, encData, oBits, customizationString)
return KEK
Here, the parameters to KMAC256 appear in the order as specified in
[SP800-186], Section 4, i.e., the key K, main input data X, requested
output length L, and optional customization string S in that order.
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Note that the values eccKeyShare defined in Section 5.1.1 and
mlkemKeyShare defined in Section 5.1.2 already use the relative
ciphertext in the derivation. The ciphertext is by design included
again in the key combiner to provide a robust security proof.
The value of domSeparation is the UTF-8 encoding of the string
"OpenPGPCompositeKeyDerivationFunction" and MUST be the following
octet sequence:
domSeparation := 4F 70 65 6E 50 47 50 43 6F 6D 70 6F 73 69 74 65
4B 65 79 44 65 72 69 76 61 74 69 6F 6E 46 75 6E
63 74 69 6F 6E
The value of counter MUST be set to the following octet sequence:
counter := 00 00 00 01
The value of fixedInfo MUST be set according to Section 5.2.1.
The value of customizationString is the UTF-8 encoding of the string
"KDF" and MUST be set to the following octet sequence:
customizationString := 4B 44 46
5.2.3. Key generation procedure
The implementation MUST independently generate the ML-KEM and the ECC
component keys. ML-KEM key generation follows the specification
[FIPS-203] and the artifacts are encoded as fixed-length octet
strings as defined in Section 5.1.2. For ECC this is done following
the relative specification in [RFC7748], [SP800-186], or [RFC5639],
and encoding the outputs as fixed-length octet strings in the format
specified in Table 5, Table 6, or Table 7.
5.2.4. Encryption procedure
The procedure to perform public-key encryption with a ML-KEM + ECC
composite scheme is as follows:
1. Take the recipient's authenticated public-key packet pkComposite
and sessionKey as input
2. Parse the algorithm ID from pkComposite
3. Extract the eccPublicKey and mlkemPublicKey component from the
algorithm specific data encoded in pkComposite with the format
specified in Section 5.3.2.
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4. Instantiate the ECC-KEM and the ML-KEM depending on the
algorithm ID according to Table 9
5. Compute (eccCipherText, eccKeyShare) := ECC-
KEM.Encaps(eccPublicKey)
6. Compute (mlkemCipherText, mlkemKeyShare) := ML-
KEM.Encaps(mlkemPublicKey)
7. Compute fixedInfo as specified in Section 5.2.1
8. Compute KEK := multiKeyCombine(eccKeyShare, eccCipherText,
mlkemKeyShare, mlkemCipherText, fixedInfo, oBits=256) as defined
in Section 5.2.2
9. Compute C := AESKeyWrap(KEK, sessionKey) with AES-256 as per
[RFC3394] that includes a 64 bit integrity check
10. Output the algorithm specific part of the PKESK as
eccCipherText || mlkemCipherText (|| symAlgId) || len(C) || C,
where both symAlgId and len(C) are single octet fields and
symAlgId denotes the symmetric algorithm ID used and is present
only for a v3 PKESK
5.2.5. Decryption procedure
The procedure to perform public-key decryption with a ML-KEM + ECC
composite scheme is as follows:
1. Take the matching PKESK and own secret key packet as input
2. From the PKESK extract the algorithm ID and the encryptedKey,
i.e., the wrapped session key
3. Check that the own and the extracted algorithm ID match
4. Parse the eccSecretKey and mlkemSecretKey from the algorithm
specific data of the own secret key encoded in the format
specified in Section 5.3.2
5. Instantiate the ECC-KEM and the ML-KEM depending on the
algorithm ID according to Table 9
6. Parse eccCipherText, mlkemCipherText, and C from encryptedKey
encoded as eccCipherText || mlkemCipherText (|| symAlgId) ||
len(C) || C as specified in Section 5.3.1, where symAlgId is
present only in the case of a v3 PKESK.
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7. Compute (eccKeyShare) := ECC-KEM.Decaps(eccCipherText,
eccSecretKey, eccPublicKey)
8. Compute (mlkemKeyShare) := ML-KEM.Decaps(mlkemCipherText,
mlkemSecretKey)
9. Compute fixedInfo as specified in Section 5.2.1
10. Compute KEK := multiKeyCombine(eccKeyShare, eccCipherText,
mlkemKeyShare, mlkemCipherText, fixedInfo, oBits=256) as defined
in Section 5.2.2
11. Compute sessionKey := AESKeyUnwrap(KEK, C) with AES-256 as per
[RFC3394], aborting if the 64 bit integrity check fails
12. Output sessionKey
5.3. Packet specifications
5.3.1. Public-Key Encrypted Session Key Packets (Tag 1)
The algorithm-specific fields consists of the output of the
encryption procedure described in Section 5.2.4:
* A fixed-length octet string representing an ECC ephemeral public
key in the format associated with the curve as specified in
Section 5.1.1.
* A fixed-length octet string of the ML-KEM ciphertext, whose length
depends on the algorithm ID as specified in Table 8.
* A one-octet size of the following fields.
* Only in the case of a v3 PKESK packet: a one-octet symmetric
algorithm identifier.
* The wrapped session key represented as an octet string.
Note that like in the case of the algorithms X25519 and X448
specified in [I-D.ietf-openpgp-crypto-refresh], for the ML-KEM
composite schemes, in the case of a v3 PKESK packet, the symmetric
algorithm identifier is not encrypted. Instead, it is placed in
plaintext after the mlkemCipherText and before the length octet
preceding the wrapped session key. In the case of v3 PKESK packets
for ML-KEM composite schemes, the symmetric algorithm used MUST be
AES-128, AES-192 or AES-256 (algorithm ID 7, 8 or 9).
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In the case of a v3 PKESK, a receiving implementation MUST check if
the length of the unwrapped symmetric key matches the symmetric
algorithm identifier, and abort if this is not the case.
5.3.2. Key Material Packets
The algorithm-specific public key is this series of values:
* A fixed-length octet string representing an EC point public key,
in the point format associated with the curve specified in
Section 5.1.1.
* A fixed-length octet string containing the ML-KEM public key,
whose length depends on the algorithm ID as specified in Table 8.
The algorithm-specific secret key is these two values:
* A fixed-length octet string of the encoded secret scalar, whose
encoding and length depend on the algorithm ID as specified in
Section 5.1.1.
* A fixed-length octet string containing the ML-KEM secret key,
whose length depends on the algorithm ID as specified in Table 8.
6. Composite Signature Schemes
6.1. Building blocks
6.1.1. EdDSA-Based signatures
To sign and verify with EdDSA the following operations are defined:
(eddsaSignature) <- EdDSA.Sign(eddsaSecretKey, dataDigest)
and
(verified) <- EdDSA.Verify(eddsaPublicKey, eddsaSignature, dataDigest)
The public and secret key, as well as the signature MUST be encoded
according to [RFC8032] as fixed-length octet strings. The following
table describes the EdDSA parameters and artifact lengths:
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+==============+=========+=======+========+========+===========+
| Algorithm ID | Curve | Field | Public | Secret | Signature |
| reference | | size | key | key | |
+==============+=========+=======+========+========+===========+
| TBD (107 for | Ed25519 | 32 | 32 | 32 | 64 |
| testing) | | | | | |
+--------------+---------+-------+--------+--------+-----------+
| TBD (108 for | Ed448 | 57 | 57 | 57 | 114 |
| testing) | | | | | |
+--------------+---------+-------+--------+--------+-----------+
Table 10: EdDSA parameters and artifact lengths in octets
6.1.2. ECDSA-Based signatures
To sign and verify with ECDSA the following operations are defined:
(ecdsaSignatureR, ecdsaSignatureS) <- ECDSA.Sign(ecdsaSecretKey,
dataDigest)
and
(verified) <- ECDSA.Verify(ecdsaPublicKey, ecdsaSignatureR,
ecdsaSignatureS, dataDigest)
The public keys MUST be encoded in SEC1 format as defined in section
Section 2.1.1. The secret key, as well as both values R and S of the
signature MUST each be encoded as a big-endian integer in a fixed-
length octet string of the specified size.
The following table describes the ECDSA parameters and artifact
lengths:
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+================+===============+=====+======+======+=========+=========+
| Algorithm ID|Curve |Field|Public|Secret|Signature|Signature|
| reference| |size |key |key |value R |value S |
+================+===============+=====+======+======+=========+=========+
|TBD (ML-DSA-65 +|NIST P-256 |32 |65 |32 |32 |32 |
| ECDSA-NIST-| | | | | | |
| P-256)| | | | | | |
+----------------+---------------+-----+------+------+---------+---------+
|TBD (ML-DSA-87 +|NIST P-384 |48 |97 |48 |48 |48 |
| ECDSA-NIST-| | | | | | |
| P-384)| | | | | | |
+----------------+---------------+-----+------+------+---------+---------+
|TBD (ML-DSA-65 +|brainpoolP256r1|32 |65 |32 |32 |32 |
| ECDSA-| | | | | | |
|brainpoolP256r1)| | | | | | |
+----------------+---------------+-----+------+------+---------+---------+
|TBD (ML-DSA-87 +|brainpoolP384r1|48 |97 |48 |48 |48 |
| ECDSA-| | | | | | |
|brainpoolP384r1)| | | | | | |
+----------------+---------------+-----+------+------+---------+---------+
Table 11: ECDSA parameters and artifact lengths in octets
6.1.3. ML-DSA signatures
For ML-DSA signature generation the default hedged version of ML-
DSA.Sign given in [FIPS-204] is used. That is, to sign with ML-DSA
the following operation is defined:
(mldsaSignature) <- ML-DSA.Sign(mldsaSecretKey, dataDigest)
For ML-DSA signature verification the algorithm ML-DSA.Verify given
in [FIPS-204] is used. That is, to verify with ML-DSA the following
operation is defined:
(verified) <- ML-DSA.Verify(mldsaPublicKey, dataDigest, mldsaSignature)
ML-DSA has the parametrization with the corresponding artifact
lengths in octets as given in Table 12. All artifacts are encoded as
defined in [FIPS-204].
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+========================+===========+========+========+===========+
| Algorithm ID reference | ML-DSA | Public | Secret | Signature |
| | | key | key | value |
+========================+===========+========+========+===========+
| TBD | ML-DSA-65 | 1952 | 4032 | 3293 |
+------------------------+-----------+--------+--------+-----------+
| TBD | ML-DSA-87 | 2592 | 4896 | 4595 |
+------------------------+-----------+--------+--------+-----------+
Table 12: ML-DSA parameters and artifact lengths in octets
6.2. Composite Signature Schemes with ML-DSA
6.2.1. Signature data digest
Signature data (i.e. the data to be signed) is digested prior to
signing operations, see [I-D.ietf-openpgp-crypto-refresh]
Section 5.2.4. Composite ML-DSA + ECC signatures MUST use the
associated hash algorithm as specified in Table 13 for the signature
data digest. Signatures using other hash algorithms MUST be
considered invalid.
An implementation supporting a specific ML-DSA + ECC algorithm MUST
also support the matching hash algorithm.
+========================+===============+===============+
| Algorithm ID reference | Hash function | Hash function |
| | | ID reference |
+========================+===============+===============+
| TBD (ML-DSA-65 IDs) | SHA3-256 | 12 |
+------------------------+---------------+---------------+
| TBD (ML-DSA-87 IDs) | SHA3-512 | 14 |
+------------------------+---------------+---------------+
Table 13: Binding between ML-DSA and signature data digest
6.2.2. Key generation procedure
The implementation MUST independently generate the ML-DSA and the ECC
component keys. ML-DSA key generation follows the specification
[FIPS-204] and the artifacts are encoded as fixed-length octet
strings as defined in Section 6.1.3. For ECC this is done following
the relative specification in [RFC7748], [SP800-186], or [RFC5639],
and encoding the artifacts as specified in Section 6.1.1 or
Section 6.1.2 as fixed-length octet strings.
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6.2.3. Signature Generation
To sign a message M with ML-DSA + EdDSA the following sequence of
operations has to be performed:
1. Generate dataDigest according to
[I-D.ietf-openpgp-crypto-refresh] Section 5.2.4
2. Create the EdDSA signature over dataDigest with EdDSA.Sign() from
Section 6.1.1
3. Create the ML-DSA signature over dataDigest with ML-DSA.Sign()
from Section 6.1.3
4. Encode the EdDSA and ML-DSA signatures according to the packet
structure given in Section 6.3.1.
To sign a message M with ML-DSA + ECDSA the following sequence of
operations has to be performed:
1. Generate dataDigest according to
[I-D.ietf-openpgp-crypto-refresh] Section 5.2.4
2. Create the ECDSA signature over dataDigest with ECDSA.Sign() from
Section 6.1.2
3. Create the ML-DSA signature over dataDigest with ML-DSA.Sign()
from Section 6.1.3
4. Encode the ECDSA and ML-DSA signatures according to the packet
structure given in Section 6.3.1.
6.2.4. Signature Verification
To verify a ML-DSA + EdDSA signature the following sequence of
operations has to be performed:
1. Verify the EdDSA signature with EdDSA.Verify() from Section 6.1.1
2. Verify the ML-DSA signature with ML-DSA.Verify() from
Section 6.1.3
To verify a ML-DSA + ECDSA signature the following sequence of
operations has to be performed:
1. Verify the ECDSA signature with ECDSA.Verify() from Section 6.1.2
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2. Verify the ML-DSA signature with ML-DSA.Verify() from
Section 6.1.3
As specified in Section 4.3 an implementation MUST validate both
signatures, i.e. EdDSA/ECDSA and ML-DSA, successfully to state that a
composite ML-DSA + ECC signature is valid.
6.3. Packet Specifications
6.3.1. Signature Packet (Tag 2)
The composite ML-DSA + ECC schemes MUST be used only with v6
signatures, as defined in [I-D.ietf-openpgp-crypto-refresh].
The algorithm-specific v6 signature parameters for ML-DSA + EdDSA
signatures consists of:
* A fixed-length octet string representing the EdDSA signature,
whose length depends on the algorithm ID as specified in Table 10.
* A fixed-length octet string of the ML-DSA signature value, whose
length depends on the algorithm ID as specified in Table 12.
The algorithm-specific v6 signature parameters for ML-DSA + ECDSA
signatures consists of:
* A fixed-length octet string of the big-endian encoded ECDSA value
R, whose length depends on the algorithm ID as specified in
Table 11.
* A fixed-length octet string of the big-endian encoded ECDSA value
S, whose length depends on the algorithm ID as specified in
Table 11.
* A fixed-length octet string of the ML-DSA signature value, whose
length depends on the algorithm ID as specified in Table 12.
6.3.2. Key Material Packets
The composite ML-DSA + ECC schemes MUST be used only with v6 keys, as
defined in [I-D.ietf-openpgp-crypto-refresh].
The algorithm-specific public key for ML-DSA + EdDSA keys is this
series of values:
* A fixed-length octet string representing the EdDSA public key,
whose length depends on the algorithm ID as specified in Table 10.
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* A fixed-length octet string containing the ML-DSA public key,
whose length depends on the algorithm ID as specified in Table 12.
The algorithm-specific secret key for ML-DSA + EdDSA keys is this
series of values:
* A fixed-length octet string representing the EdDSA secret key,
whose length depends on the algorithm ID as specified in Table 10.
* A fixed-length octet string containing the ML-DSA secret key,
whose length depends on the algorithm ID as specified in Table 12.
The algorithm-specific public key for ML-DSA + ECDSA keys is this
series of values:
* A fixed-length octet string representing the ECDSA public key in
SEC1 format, as specified in section Section 2.1.1 and with length
specified in Table 11.
* A fixed-length octet string containing the ML-DSA public key,
whose length depends on the algorithm ID as specified in Table 12.
The algorithm-specific secret key for ML-DSA + ECDSA keys is this
series of values:
* A fixed-length octet string representing the ECDSA secret key as a
big-endian encoded integer, whose length depends on the algorithm
used as specified in Table 11.
* A fixed-length octet string containing the ML-DSA secret key,
whose length depends on the algorithm ID as specified in Table 12.
7. SLH-DSA
7.1. The SLH-DSA Algorithms
The following table describes the SLH-DSA parameters and artifact
lengths:
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+==============+=============+============+============+===========+
| Parameter ID | Parameter | SLH-DSA | SLH-DSA | SLH-DSA |
| reference | name suffix | public key | secret key | signature |
+==============+=============+============+============+===========+
| 1 | 128s | 32 | 64 | 7856 |
+--------------+-------------+------------+------------+-----------+
| 2 | 128f | 32 | 64 | 17088 |
+--------------+-------------+------------+------------+-----------+
| 3 | 192s | 48 | 96 | 16224 |
+--------------+-------------+------------+------------+-----------+
| 4 | 192f | 48 | 96 | 35664 |
+--------------+-------------+------------+------------+-----------+
| 5 | 256s | 64 | 128 | 29792 |
+--------------+-------------+------------+------------+-----------+
| 6 | 256f | 64 | 128 | 49856 |
+--------------+-------------+------------+------------+-----------+
Table 14: SLH-DSA parameters and artifact lengths in octets.
The values equally apply to the parameter IDs of SLH-DSA-SHA2
and SLH-DSA-SHAKE.
7.1.1. Signature Data Digest
Signature data (i.e. the data to be signed) is digested prior to
signing operations, see [I-D.ietf-openpgp-crypto-refresh]
Section 5.2.4. SLH-DSA signatures MUST use the associated hash
algorithm as specified in Table 15 for the signature data digest.
Signatures using other hash algorithms MUST be considered invalid.
An implementation supporting a specific SLH-DSA algorithm and
parameter MUST also support the matching hash algorithm.
+========================+==============+==========+===============+
| Algorithm ID reference | Parameter ID | Hash | Hash function |
| | reference | function | ID reference |
+========================+==============+==========+===============+
| TBD (109 for testing) | 1, 2 | SHA-256 | 8 |
+------------------------+--------------+----------+---------------+
| TBD (109 for testing) | 3, 4, 5, 6 | SHA-512 | 10 |
+------------------------+--------------+----------+---------------+
| TBD (SLH-DSA-SHAKE) | 1, 2 | SHA3-256 | 12 |
+------------------------+--------------+----------+---------------+
| TBD (SLH-DSA-SHAKE) | 3, 4, 5, 6 | SHA3-512 | 14 |
+------------------------+--------------+----------+---------------+
Table 15: Binding between SLH-DSA and signature data digest
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7.1.2. Key generation
SLH-DSA key generation is performed via the algorithm SLH-DSA.KeyGen
as specified in [FIPS-205], and the artifacts are encoded as fixed-
length octet strings as defined in Section 7.1.
7.1.3. Signature Generation
SLH-DSA signature generation is performed via the algorithm SLH-
DSA.Sign as specified in [FIPS-205]. The variable opt_rand is set to
PK.seed. See also Section 10.5.
An implementation MUST set the Parameter ID in the signature equal to
the issuing secret key Parameter ID.
7.1.4. Signature Verification
SLH-DSA signature verification is performed via the algorithm SLH-
DSA.Verify as specified in [FIPS-205].
An implementation MUST check that the Parameter ID in the signature
and in the key match when verifying.
7.2. Packet specifications
7.2.1. Signature Packet (Tag 2)
The SLH-DSA scheme MUST be used only with v6 signatures, as defined
in [I-D.ietf-openpgp-crypto-refresh] Section 5.2.3.
The algorithm-specific v6 Signature parameters consists of:
* A one-octet value specifying the SLH-DSA parameter ID defined in
Table 3 and Table 4. The values 0x00 and 0xFF are reserved for
future extensions.
* A fixed-length octet string of the SLH-DSA signature value, whose
length depends on the parameter ID in the format specified in
Table 14.
7.2.2. Key Material Packets
The SLH-DSA scheme MUST be used only with v6 keys, as defined in
[I-D.ietf-openpgp-crypto-refresh].
The algorithm-specific public key is this series of values:
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* A one-octet value specifying the SLH-DSA parameter ID defined in
Table 3 and Table 4. The values 0x00 and 0xFF are reserved for
future extensions.
* A fixed-length octet string containing the SLH-DSA public key,
whose length depends on the parameter ID as specified in Table 14.
The algorithm-specific secret key is this value:
* A fixed-length octet string containing the SLH-DSA secret key,
whose length depends on the parameter ID as specified in Table 11.
8. Notes on Algorithms
8.1. Symmetric Algorithms for SEIPD Packets
Implementations MUST implement AES-256. An implementation SHOULD use
AES-256 in the case of a v1 SEIPD packet, or AES-256 with any
available AEAD mode in the case of a v2 SEIPD packet, if all
recipients indicate support for it (explicitly or implicitly).
A v4 or v6 certificate that contains a PQ(/T) key SHOULD include
AES-256 in the "Preferred Symmetric Ciphers for v1 SEIPD" subpacket.
A v6 certificate that contains a PQ(/T) key SHOULD include the pair
AES-256 with OCB in the "Preferred AEAD Ciphersuites" subpacket.
If AES-256 is not explicitly in the list of the "Preferred Symmetric
Ciphers for v1 SEIPD" subpacket, and if the certificate contains a
PQ/T key, it is implicitly at the end of the list. This is justified
since AES-256 is mandatory to implement. If AES-128 is also
implictly added to the list, it is added after AES-256.
If the pair AES-256 with OCB is not explicitly in the list of the
"Preferred AEAD Ciphersuites" subpacket, and if the certificate
contains a PQ/T key, it is implicitly at the end of the list. This
is justified since AES-256 and OCB are mandatory to implement. If
the pair AES-128 with OCB is also implictly added to the list, it is
added after the pair AES-256 with OCB.
9. Migration Considerations
The post-quantum KEM algorithms defined in Table 1 and the signature
algorithms defined in Table 2 are a set of new public key algorithms
that extend the algorithm selection of
[I-D.ietf-openpgp-crypto-refresh]. During the transition period, the
post-quantum algorithms will not be supported by all clients.
Therefore various migration considerations must be taken into
account, in particular backwards compatibility to existing
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implementations that have not yet been updated to support the post-
quantum algorithms.
9.1. Key preference
Implementations SHOULD prefer PQ(/T) keys when multiple options are
available.
For instance, if encrypting for a recipient for which both a valid
PQ/T and a valid ECC certificate are available, the implementation
SHOULD choose the PQ/T certificate. In case a certificate has both a
PQ/T and an ECC encryption-capable valid subkey, the PQ/T subkey
SHOULD be preferred.
An implementation MAY sign with both a PQ(/T) and an ECC key using
multiple signatures over the same data as described in Section 4.4.
Signing only with PQ(/T) key material is not backwards compatible.
Note that the confidentiality of a message is not post-quantum secure
when encrypting to multiple recipients if at least one recipient does
not support PQ/T encryption schemes. An implementation SHOULD NOT
abort the encryption process in this case to allow for a smooth
transition to post-quantum cryptography.
9.2. Key generation strategies
It is RECOMMENDED to generate fresh secrets when generating PQ(/T)
keys. Note that reusing key material from existing ECC keys in
PQ(/T) keys does not provide backwards compatibility.
An OpenPGP certificate is composed of a certification-capable primary
key and one or more subkeys for signature, encryption, and
authentication. Two migration strategies are recommended:
1. Generate two independent certificates, one for PQ(/T)-capable
implementations, and one for legacy implementations.
Implementations not understanding PQ(/T) certificates can use the
legacy certificate, while PQ(/T)-capable implementations will
prefer the newer certificate. This allows having an older v4 or
v6 certificate for compatibility and a v6 PQ(/T) certificate, at
a greater complexity in key distribution.
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2. Attach PQ(/T) encryption subkeys to an existing traditional
OpenPGP certificate. In the case of a v6 certificate, also
PQ(/T) signature keys may be attached. Implementations
understanding PQ(/T) will be able to parse and use the subkeys,
while PQ(/T)-incapable implementations can gracefully ignore
them. This simplifies key distribution, as only one certificate
needs to be communicated and verified, but leaves the primary key
vulnerable to quantum computer attacks.
10. Security Considerations
10.1. Security Aspects of Composite Signatures
When multiple signatures are applied to a message, the question of
the protocol's resistance against signature stripping attacks
naturally arises. In a signature stripping attack, an adversary
removes one or more of the transmitted signatures such that only a
subset of the signatures originally applied by the sender remain in
the message that reaches the recipient. This amounts to a downgrade
attack that potentially reduces the value of the signature. It
should be noted that the composite signature schemes specified in
this draft are not subject to a signature stripping vulnerability.
This is due to the fact that in any OpenPGP signature, the hashed
meta data includes the signature algorithm ID, as specified in
[I-D.ietf-openpgp-crypto-refresh], Section 5.2.4. As a consequence,
a component signature taken out of the context of a specific
composite algorithm is not a valid signature for any message.
Furthermore, it is also not possible to craft a new signature for a
message that was signed twice with a composite algorithm by
interchanging (i.e., remixing) the component signatures, which would
classify as a weak existential forgery. This is due to the fact that
each v6 signatures also includes a random salt at the start of the
hashed meta data, as also specified in the aforementioned reference.
10.2. Hashing in ECC-KEM
Our construction of the ECC-KEMs, in particular the inclusion of
eccCipherText in the final hashing step in encapsulation and
decapsulation that produces the eccKeyShare, is standard and known as
hashed ElGamal key encapsulation, a hashed variant of ElGamal
encryption. It ensures IND-CCA2 security in the random oracle model
under some Diffie-Hellman intractability assumptions [CS03]. The
additional inclusion of eccPublicKey follows the security advice in
Section 6.1 of [RFC7748].
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10.3. Key combiner
For the key combination in Section 5.2.2 this specification limits
itself to the use of KMAC. The sponge construction used by KMAC was
proven to be indifferentiable from a random oracle [BDPA08]. This
means, that in contrast to SHA2, which uses a Merkle-Damgard
construction, no HMAC-based construction is required for key
combination. Except for a domain separation it is sufficient to
simply process the concatenation of any number of key shares when
using a sponge-based construction like KMAC. The construction using
KMAC ensures a standardized domain separation. In this case, the
processed message is then the concatenation of any number of key
shares.
More precisely, for a given capacity c the indifferentiability proof
shows that assuming there are no weaknesses found in the Keccak
permutation, an attacker has to make an expected number of 2^(c/2)
calls to the permutation to tell KMAC from a random oracle. For a
random oracle, a difference in only a single bit gives an unrelated,
uniformly random output. Hence, to be able to distinguish a key K,
derived from shared keys K1 and K2 (and ciphertexts C1 and C2) as
K = KMAC(domainSeparation, counter || K1 || C1 || K2 || C2 || fixedInfo,
outputBits, customization)
from a random bit string, an adversary has to know (or correctly
guess) both key shares K1 and K2, entirely.
The proposed construction in Section 5.2.2 preserves IND-CCA2 of any
of its ingredient KEMs, i.e. the newly formed combined KEM is IND-
CCA2 secure as long as at least one of the ingredient KEMs is.
Indeed, the above stated indifferentiability from a random oracle
qualifies Keccak as a split-key pseudorandom function as defined in
[GHP18]. That is, Keccak behaves like a random function if at least
one input shared secret is picked uniformly at random. Our
construction can thus be seen as an instantiation of the IND-CCA2
preserving Example 3 in Figure 1 of [GHP18], up to some reordering of
input shared secrets and ciphertexts. In the random oracle setting,
the reordering does not influence the arguments in [GHP18].
10.4. Domain separation and binding
The domSeparation information defined in Section 5.2.2 provides the
domain separation for the key combiner construction. This ensures
that the input keying material is used to generate a KEK for a
specific purpose or context.
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The fixedInfo defined in Section 5.2.1 binds the derived KEK to the
chosen algorithm and communication parties. The algorithm ID
identifies unequivocally the algorithm, the parameters for its
instantiation, and the length of all artifacts, including the derived
key.
This is in line with the Recommendation for ECC in section 5.5 of
[SP800-56A]. Other fields included in the recommendation are not
relevant for the OpenPGP protocol, since the sender is not required
to have a key of their own, there are no pre-shared secrets, and all
the other parameters are unequivocally defined by the algorithm ID.
Furthermore, we do not require the recipients public key into the key
combiner as the public key material is already included in the
component key derivation functions. Given two KEMs which we assume
to be multi-user secure, we combine their outputs using a KEM-
combiner:
K = H(K1, C1, K2, C2), C = (C1, C2)
Our aim is to preserve multi-user security. A common approach to
this is to add the public key into the key derivation for K.
However, it turns out that this is not necessary here. To break
security of the combined scheme in the multi-user setting, the
adversary has to distinguish a set of challenge keys
K__u = H(K1__u, C1__u, K2__u, C2*_u)
for users u in some set from random, also given ciphertexts C*_u =
(C1*_u, C2*_u). For each of these K* it holds that if the adversary
never makes a query
H(K1*_u, C1*_u, K2*_u, C2*_u)
they have a zero advantage over guessing.
The only multi-user advantage that the adversary could gain therefore
consists of queries to H that are meaningful for two different users
u1 != u2 and their associated public keys. This is only the case if
(c1*_u1, c2*_u1) = (c1*_u2, c2*_u2)
as the ciphertext values decide for which challenge the query is
meaningful. This means that a ciphertext collision is needed between
challenges. Assuming that the randomness used in the generation of
the two challenges is uncorrelated, this is negligible.
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In consequence, the ciphertexts already work sufficiently well as
domain-separator.
10.5. SLH-DSA Message Randomizer
The specification of SLH-DSA [FIPS-205] prescribes an optional non-
deterministic message randomizer. This is not used in this
specification, as OpenPGP v6 signatures already provide a salted
signature data digest of the appropriate size.
10.6. Binding hashes in signatures with signature algorithms
In order not to extend the attack surface, we bind the hash algorithm
used for signature data digestion to the hash algorithm used
internally by the signature algorithm.
ML-DSA internally uses a SHAKE256 digest, therefore we require SHA3
in the ML-DSA + ECC signature packet, see Section 6.2.1. Note that
we bind a NIST security category 2 hash function to a signature
algorithm that falls into NIST security category 3. This does not
constitute a security bottleneck: because of the unpredictable random
salt that is prepended to the digested data in v6 signatures, the
hardness assumption is not collision resistance but second-preimage
resistance.
In the case of SLH-DSA the internal hash algorithm varies based on
the algorithm and parameter ID, see Section 7.1.1.
10.7. Symmetric Algorithms for SEIPD Packets
This specification mandates support for AES-256 for two reasons.
First, AES-KeyWrap with AES-256 is already part of the composite KEM
construction. Second, some of the PQ(/T) algorithms target the
security level of AES-256.
For the same reasons, this specification further recommends the use
of AES-256 if it is supported by all recipients, regardless of what
the implementation would otherwise choose based on the recipients'
preferences. This recommendation should be understood as a clear and
simple rule for the selection of AES-256 for encryption.
Implementations may also make more nuanced decisions.
11. Additional considerations
11.1. Performance Considerations for SLH-DSA
This specification introduces both ML-DSA + ECC as well as SLH-DSA as
PQ(/T) signature schemes.
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Generally, it can be said that ML-DSA + ECC provides a performance in
terms of execution time requirements that is close to that of
traditional ECC signature schemes. Regarding the size of signatures
and public keys, though, ML-DSA has far greater requirements than
traditional schemes like EC-based or even RSA signature schemes.
Implementers may want to offer SLH-DSA for applications where a
higher degree of trust in the signature scheme is required. However,
SLH-DSA has performance characteristics in terms of execution time of
the signature generation as well as space requirements for the
signature that are even greater than those of ML-DSA + ECC signature
schemes.
Pertaining to the execution time, the particularly costly operation
in SLH-DSA is the signature generation. In order to achieve short
signature generation times, one of the parameter sets with the name
ending in the letter "f" for "fast" should be chosen. This comes at
the expense of a larger signature size.
In order to minimize the space requirements of a SLH-DSA signature, a
parameter set ending in "s" for "small" should be chosen. This comes
at the expense of a longer signature generation time.
12. IANA Considerations
IANA is requested to add the following registries to the OpenPGP
registry group at https://www.iana.org/assignments/openpgp:
* Registry name: OpenPGP SLH-DSA-SHA2 parameters
Registration procedure: SPECIFICATION REQUIRED [RFC8126]
The registry contains the values defined in Table 3 in this
document.
* Registry name: OpenPGP SLH-DSA-SHAKE parameters
Registration procedure: SPECIFICATION REQUIRED [RFC8126]
The registry contains the values defined in Table 4 in this
document.
Furthermore, IANA is requested to add the algorithm IDs defined in
Table 16 to the existing registry OpenPGP Public Key Algorithms. The
field specifications enclosed in brackets for the ML-KEM + ECDH
composite algorithms denote fields that are only conditionally
contained in the data structure.
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+===+=========+=========+=========+=========+============+=========+
|ID |Algorithm| Public| Secret|Signature|PKESK Format|Reference|
| | | Key| Key| Format| | |
| | | Format| Format| | | |
+===+=========+=========+=========+=========+============+=========+
|TBD|ML- |32 octets|32 octets| N/A| 32 octets| Section|
| |KEM-768 +| X25519| X25519| | X25519| 5.2|
| |X25519 | public| secret| | ciphertext,| |
| | | key| key| | 1088 octets| |
| | | (Table| (Table| | ML-KEM-768| |
| | | 5), 1184| 5), 2400| | ciphertext| |
| | | octets| octets| | [, 1 octet| |
| | | ML-| ML-| |algorithm ID| |
| | | KEM-768| KEM-768| | in case of| |
| | | public| secret-| |v3 PKESK], 1| |
| | | key| key| |octet length| |
| | |(Table 8)|(Table 8)| | field of| |
| | | | | | value n, n| |
| | | | | | octets| |
| | | | | | wrapped| |
| | | | | | session key| |
| | | | | | (Section| |
| | | | | | 5.3.1)| |
+---+---------+---------+---------+---------+------------+---------+
|TBD|ML- |56 octets|56 octets| N/A| 56 octets| Section|
| |KEM-1024 | X448| X448| | X448| 5.2|
| |+ X448 | public| secret| | ciphertext,| |
| | | key| key| | 1568 octets| |
| | | (Table| (Table| | ML-KEM-1024| |
| | | 5), 1568| 5), 3168| | ciphertext| |
| | | octets| octets| | [, 1 octet| |
| | | ML-| ML-| |algorithm ID| |
| | | KEM-1024| KEM-1024| | in case of| |
| | | public| secret-| |v3 PKESK], 1| |
| | | key| key| |octet length| |
| | |(Table 8)|(Table 8)| | field of| |
| | | | | | value n, n| |
| | | | | | octets| |
| | | | | | wrapped| |
| | | | | | session key| |
| | | | | | (Section| |
| | | | | | 5.3.1)| |
+---+---------+---------+---------+---------+------------+---------+
|TBD|ML-DSA-65|32 octets|32 octets|64 octets| N/A| Section|
| |+ Ed25519| Ed25519| Ed25519| Ed25519| | 6.2|
| | | public| secret|signature| | |
| | | key| key| (Table| | |
| | | (Table| (Table|10), 3293| | |
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| | |10), 1952|10), 4032| octets| | |
| | | octets| octets|ML-DSA-65| | |
| | |ML-DSA-65|ML-DSA-65|signature| | |
| | | public| secret| (Table| | |
| | | key| (Table| 12)| | |
| | | (Table| 12)| | | |
| | | 12)| | | | |
+---+---------+---------+---------+---------+------------+---------+
|TBD|ML-DSA-87|57 octets|57 octets| 114| N/A| Section|
| |+ Ed448 | Ed448| Ed448| octets| | 6.2|
| | | public| secret| Ed448| | |
| | | key| key|signature| | |
| | | (Table| (Table| (Table| | |
| | |10), 2592|10), 4896|10), 4595| | |
| | | octets| octets| octets| | |
| | |ML-DSA-87|ML-DSA-87|ML-DSA-87| | |
| | | public| secret|signature| | |
| | | key| (Table| (Table| | |
| | | (Table| 12)| 12)| | |
| | | 12)| | | | |
+---+---------+---------+---------+---------+------------+---------+
|TBD|SLH-DSA- | 1 octet| per| 1 octet| N/A| Section|
| |SHA2 |parameter|parameter|parameter| | 7.1|
| | | ID, per| fixed-| ID, per| | |
| | |parameter| length|parameter| | |
| | | fixed-| octet| fixed-| | |
| | | length| string| length| | |
| | | octet| (Table| octet| | |
| | | string| 14)| string| | |
| | | (Table| | (Table| | |
| | | 14)| | 14)| | |
+---+---------+---------+---------+---------+------------+---------+
|TBD|SLH-DSA- | 1 octet| per| 1 octet| N/A| Section|
| |SHAKE |parameter|parameter|parameter| | 7.1|
| | | ID, per| fixed-| ID, per| | |
| | |parameter| length|parameter| | |
| | | fixed-| octet| fixed-| | |
| | | length| string| length| | |
| | | octet| (Table| octet| | |
| | | string| 14)| string| | |
| | | (Table| | (Table| | |
| | | 14)| | 14)| | |
+---+---------+---------+---------+---------+------------+---------+
Table 16: IANA updates for registry 'OpenPGP Public Key Algorithms'
13. Changelog
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13.1. draft-wussler-openpgp-pqc-01
* Shifted the algorithm IDs by 4 to align with the crypto-refresh.
* Renamed v5 packets into v6 to align with the crypto-refresh.
* Defined IND-CCA2 security for KDF and key combination.
* Added explicit key generation procedures.
* Changed the key combination KMAC salt.
* Mandated Parameter ID check in SPHINCS+ signature verification.
* Fixed key share size for Kyber-768.
* Added "Preliminaries" section.
* Fixed IANA considerations.
13.2. draft-wussler-openpgp-pqc-02
* Added the ephemeral and public key in the ECC key derivation
function.
* Removed public key hash from key combiner.
* Allowed v3 PKESKs and v4 keys with PQ algorithms, limiting them to
AES symmetric ciphers. for encryption with SEIPDv1, in line with
the crypto-refresh.
13.3. draft-wussler-openpgp-pqc-03
* Replaced round 3 submission with NIST PQC Draft Standards FIPS
203, 204, 205.
* Added consideration about security level for hashes.
13.4. draft-wussler-openpgp-pqc-04
* Added Johannes Roth as author
13.5. draft-ietf-openpgp-pqc-00
* Renamed draft
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13.6. draft-ietf-openpgp-pqc-01
* Mandated AES-256 as mandatory to implement.
* Added AES-256 / AES-128 with OCB implicitly to v1/v2 SEIPD
preferences of "PQ(/T) certificates".
* Added a recommendation to use AES-256 when possible.
* Swapped the optional v3 PKESK algorithm identifier with length
octet in order to align with X25519 and X448.
* Fixed ML-DSA private key size
* Added test vectors
* correction and completion of IANA instructions
13.7. draft-ietf-openpgp-pqc-02
* Removed git rebase artifact
14. Contributors
Stephan Ehlen (BSI)
Carl-Daniel Hailfinger (BSI)
Andreas Huelsing (TU Eindhoven)
15. References
15.1. Normative References
[I-D.ietf-openpgp-crypto-refresh]
Wouters, P., Huigens, D., Winter, J., and N. Yutaka,
"OpenPGP", Work in Progress, Internet-Draft, draft-ietf-
openpgp-crypto-refresh-13, 4 January 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-
crypto-refresh-13>.
[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>.
[RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
for Security", RFC 7748, DOI 10.17487/RFC7748, January
2016, <https://www.rfc-editor.org/rfc/rfc7748>.
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[RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
Signature Algorithm (EdDSA)", RFC 8032,
DOI 10.17487/RFC8032, January 2017,
<https://www.rfc-editor.org/rfc/rfc8032>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/rfc/rfc8126>.
15.2. Informative References
[BDPA08] Bertoni, G., Daemen, J., Peters, M., and G. Assche, "On
the Indifferentiability of the Sponge Construction", 2008,
<https://doi.org/10.1007/978-3-540-78967-3_11>.
[CS03] Cramer, R. and V. Shoup, "Design and Analysis of Practical
Public-Key Encryption Schemes Secure against Adaptive
Chosen Ciphertext Attack", 2003,
<https://doi.org/10.1137/S0097539702403773>.
[draft-driscoll-pqt-hybrid-terminology]
Driscoll, F., "Terminology for Post-Quantum Traditional
Hybrid Schemes", March 2023,
<https://datatracker.ietf.org/doc/html/draft-driscoll-pqt-
hybrid-terminology>.
[FIPS-203] National Institute of Standards and Technology, "Module-
Lattice-Based Key-Encapsulation Mechanism Standard",
August 2023, <https://doi.org/10.6028/NIST.FIPS.203.ipd>.
[FIPS-204] National Institute of Standards and Technology, "Module-
Lattice-Based Digital Signature Standard", August 2023,
<https://doi.org/10.6028/NIST.FIPS.204.ipd>.
[FIPS-205] National Institute of Standards and Technology, "Stateless
Hash-Based Digital Signature Standard", August 2023,
<https://doi.org/10.6028/NIST.FIPS.205.ipd>.
[GHP18] Giacon, F., Heuer, F., and B. Poettering, "KEM Combiners",
2018, <https://doi.org/10.1007/978-3-319-76578-5_7>.
[NIST-PQC] Chen, L., Moody, D., and Y. Liu, "Post-Quantum
Cryptography Standardization", December 2016,
<https://csrc.nist.gov/projects/post-quantum-cryptography/
post-quantum-cryptography-standardization>.
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[NISTIR-8413]
Alagic, G., Apon, D., Cooper, D., Dang, Q., Dang, T.,
Kelsey, J., Lichtinger, J., Miller, C., Moody, D.,
Peralta, R., Perlner, R., Robinson, A., Smith-Tone, D.,
and Y. Liu, "Status Report on the Third Round of the NIST
Post-Quantum Cryptography Standardization Process", NIST
IR 8413 , September 2022,
<https://doi.org/10.6028/NIST.IR.8413-upd1>.
[RFC5639] Lochter, M. and J. Merkle, "Elliptic Curve Cryptography
(ECC) Brainpool Standard Curves and Curve Generation",
RFC 5639, DOI 10.17487/RFC5639, March 2010,
<https://www.rfc-editor.org/rfc/rfc5639>.
[SEC1] Standards for Efficient Cryptography Group, "Standards for
Efficient Cryptography 1 (SEC 1)", May 2009,
<https://secg.org/sec1-v2.pdf>.
[SP800-185]
Kelsey, J., Chang, S., and R. Perlner, "SHA-3 Derived
Functions: cSHAKE, KMAC, TupleHash, and ParallelHash",
NIST Special Publication 800-185 , December 2016,
<https://doi.org/10.6028/NIST.SP.800-185>.
[SP800-186]
Chen, L., Moody, D., Regenscheid, A., and K. Randall,
"Recommendations for Discrete Logarithm-Based
Cryptography: Elliptic Curve Domain Parameters", NIST
Special Publication 800-186 , February 2023,
<https://doi.org/10.6028/NIST.SP.800-186>.
[SP800-56A]
Barker, E., Chen, L., Roginsky, A., Vassilev, A., and R.
Davis, "Recommendation for Pair-Wise Key-Establishment
Schemes Using Discrete Logarithm Cryptography", NIST
Special Publication 800-56A Rev. 3 , April 2018,
<https://doi.org/10.6028/NIST.SP.800-56Ar3>.
[SP800-56C]
Barker, E., Chen, L., and R. Davis, "Recommendation for
Key-Derivation Methods in Key-Establishment Schemes", NIST
Special Publication 800-56C Rev. 2 , August 2020,
<https://doi.org/10.6028/NIST.SP.800-56Cr2>.
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Appendix A. Test Vectors
To help implementing this specification a set of non-normative
examples follow here. The test vectors are implemented using the
Initial Public Draft (IPD) variant of the ML-DSA and ML-KEM schemes.
A.1. Sample v6 PQC Subkey Artifacts
Here is a Private Key consisting of:
* A v6 Ed25519 Private-Key packet
* A v6 direct key self-signature
* A User ID packet
* A v6 positive certification self-signature
* A v6 ML-KEM-ipd-768 + X25519 Private-Subkey packet
* A v6 subkey binding signature
The primary key has the fingerprint
52343242345254050219ceff286e9c8e479ec88757f95354388984a02d7d0b59.
The subkey has the fingerprint
263e34b69938e753dc67ca8ee37652795135e0e16e48887103c11d7307df40ed.
-----BEGIN PGP PRIVATE KEY BLOCK-----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WmAKkyo7kWAwYRsE2ZYqLzIJFmZFzRLIThipiZhR/9h2GemQklMJqYs25cEGx6FW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4lTxEWgjR1kR1RHBqgghNaK2V209Sa0G4myFx4QNJaim7AvMG5VOdgOlPL3hm0ME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-----END PGP PRIVATE KEY BLOCK-----
Here is the corresponding Public Key consisting of:
* A v6 Ed25519 Public-Key packet
* A v6 direct key self-signature
* A User ID packet
* A v6 positive certification self-signature
* A v6 ML-KEM-ipd-768 + X25519 Public-Subkey packet
* A v6 subkey binding signature
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-----BEGIN PGP PUBLIC KEY BLOCK-----
xioGUdDGgBsAAAAgsJV1qyvdl+EenEB4IFvP5/7Ci5XJ1rk8Yh967qV1rb3CrwYf
GwoAAABABQJR0MaAIqEGUjQyQjRSVAUCGc7/KG6cjkeeyIdX+VNUOImEoC19C1kC
GwMCHgkDCwkHAxUKCAIWAAUnCQIHAgAAAADhOyBW8CPDe5FreFmlonhfVhr2EPw3
WFLyd6mKRhkQm3VBfw7Qw7eermL9Cr5O7Ah0JxmIkT18jgKQr9AwWa3nm2mcbjSo
ib2WVzm5EiW3f3lgflfrySQFpSICzPl2QcAcrgjNLlBRQyB1c2VyIChUZXN0IEtl
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xoBpAAAEwLRbSSpvve2pIh3hHweqq2VdRo+7Zf7whYHyXM/UifsniwMKSrubvsmL
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vksx59ZtLFtBgHm5eRmYYleJsJLGCPssa7pK2hIwgLlmCLSAavFqYjuocWIYKLmw
5vNXXRWIjPBbTpVXbUO5U9F/67gggSWBJXCZlfgcluO422aN22m8aONiTgZtmjcC
2elci5yRKGBbeKmFTcVsZbpbY6ZCKFRyzbqmMGYe0mqN6lh7R5dNiBuJZQg04mYu
SzWCF3mumlJTRtlN9Miy6LyWApJSTQdgc3awS0mjUrgU1Ia0AjMFKcxJA6iHd6iA
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NOBiUhNUC/aYIILEm7qjTpw5YdI+6jSl+palLlcMDzt0LgMN8rY6UlZJBGNFSAKS
NSWXdFYMByKKGSCj91TDWPlOLvWKntSLk5eLodhgmRGqx5GZECgWS4wDARY00rl1
7dV53GejXrUtJaYcnam5pKoTSaPJTuY25Kyy+oB7aHpV0vA87JaeRCsqkjcS5IQK
dtceUskXNRa2f7CTrfQRhOGk0gSA4Jx8+Fw8uGWLGJx6m1lSyWcMX5HL7hJkFhEK
ebYjdALGXMV1wxNiUHCIvxCjX/AkwHEDvAN6qhULrcZlmngSbeBysOFud2a8PIS2
p7RCAatO+TpFgoR+1CgVJIdiRpM0WrMfS9iBERhtYaLH1oUjBpcV7zpgNdkT4Clf
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4jxTd/FwQ3pDoKxTesY+XsGtVJxe9oMrXSlt6uymn6zKQlQsw8odvHhp5/NWqkCh
9/xQvmIlERsVVjyJ0FNF/+HNT9KrECCj6+cujDbEN6UmRlFvlMcxFzYaTnWa1csh
SVCCa1aYZddWrDdxOwMfObUw8TukY7A2RqcdpmpA68SLoWwNAgtFG1xWV43yC/P3
XTsqTmgHRUGboDkVs9K81+Byg4jhKWfCmwYYGwoAAAAsBQJR0MaAIqEGUjQyQjRS
VAUCGc7/KG6cjkeeyIdX+VNUOImEoC19C1kCGwwAAAAA5kEgPwatbx3FHPIy9J9m
GUEpUE03oRRPE8N4lJ2eAIMhciCEHp3BzYVGvW3OaPYmjcu4JTREPJM6HP7yR+ZE
g+Bld9lBSVmEdMJnOX2ZHOdEoRV4bm1U4aPuhrKL/d8lkIgM
-----END PGP PUBLIC KEY BLOCK-----
Here is an unsigned message "Testing\n" encrypted to this key:
* A v6 PKESK
* A v2 SEIPD
Kousidis, et al. Expires 5 September 2024 [Page 50]
Internet-Draft PQC in OpenPGP March 2024
The hex-encoded KMAC eccKeyShare input is
4ec7dc0874ce4a3c257fec94f27f2d3c589764a5fbaf27a4b52836df53c86868.
The hex-encoded KMAC mlkemKeyShare input is
9a84cb01b6be6eecd16737fb558b5ca35899403076c7e9f0ee350195e7fbf6c4.
The hex-encoded KMAC256 output is
15a0f1eed1fb2a50a22f21e82dbce13ae91c45e3b76a9d2c61246c354a05f781.
The hex-encoded session key is
08f49fd5340b026e7ec751d82cea83a4b92d4837e785bfb66af71387f84156d0.
-----BEGIN PGP MESSAGE-----
wcPtBiEGJj40tpk451PcZ8qO43ZSeVE14OFuSIhxA8EdcwffQO1pU4rRGXPhivmf
yaE7whd94FIPayIJxbUXuq6Ei6VifzlPu9BoxvQYZa/u+exaOVT2MLxbCAceHYMw
zSuUa0BoiugafZWAnVrn4ji+mI+298c93Ij83yUjkzvBsKyJuhesTevSpJAnjiMt
m9Mmwzc8Y9tB4N/Am8jR3p8UYLH+2aH9FyT6VdqsETYiPFcz5jZqkag7bAB88KUg
heJAHU/FgHXtz013tnPyQPtuVHeJrP8jcd3IENJh9CfSg9rkhAoW72GiSGYPm+Im
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HScy59zUR5CoYnJNBDNyRyEuh/B/pkTGEisLb+i1F9M0WhrgfgYSldEzUCZ7KJUD
Bt/d50OM+M8kmkYYBmiyWBfNqMMckJHhjFAp8kd0V0FP7lVwPGywK2hGKQBF+ylh
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1lXSx7uZFCfhyu96hyIPxMuaBIX7OHkduinurQ58Vj92fAe/8f5jviRVqtKwZ9Ao
lZfjSn8k/CgDxzFu2gWpbhWJ4GKvoXgmWDESk4o07UGqDbhm0YO5MDM0uoAmsGae
0lQCCQIMTzhupJq1yZ3vljrXBYF37QuWDi/MAvL54hMis5UXrTAh0+FobZAXCoO0
epU7H8CIs4ZCelIyD1W+K/kv3/E3Z65WQzDOYOhXSCAOqcpjiPc=
-----END PGP MESSAGE-----
A.2. V4 PQC Subkey Artifacts
Here is a Private Key consisting of:
* A v4 Ed25519 Private-Key packet
Kousidis, et al. Expires 5 September 2024 [Page 51]
Internet-Draft PQC in OpenPGP March 2024
* A User ID packet
* A v4 positive certification self-signature
* A v4 ECDH (Curve25519) Private-Subkey packet
* A v4 subkey binding signature
* A v4 ML-KEM-ipd-768 + X25519 Private-Subkey packet
* A v4 subkey binding signature
The primary key has the fingerprint
b2e9b532d55bd6287ec79e17c62adc0ddd1edd73.
The ECDH subkey has the fingerprint
95bed3c63f295e7b980b6a2b93b3233faf28c9d2.
The ML-KEM-ipd-768 + X25519 subkey has the fingerprint
bd67d98388813e88bf3490f3e440cfbaffd6f357.
-----BEGIN PGP PRIVATE KEY BLOCK-----
xVgEUdDGgBYJKwYBBAHaRw8BAQdAhoSK5cJt9N37EE1UjPqp8EXhAvOBCYikgtcg
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xoASCisGAQQBl1UBBQEBB0Dfrrz6gEv3iM2ULhupwUD4qABPIAwaNyVYDT2euXaS
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ACoFAlHQxoAJEMYq3A3dHt1zFiEEsum1MtVb1ih+x54XxircDd0e3XMCGwwAAI/D
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tIQ4HmCADposq1OTiAbxfYP6RtiLyemxDJaFLdaDSRSXIf5ALgxaysUxe57Qh7uA
Kousidis, et al. Expires 5 September 2024 [Page 52]
Internet-Draft PQC in OpenPGP March 2024
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Kousidis, et al. Expires 5 September 2024 [Page 53]
Internet-Draft PQC in OpenPGP March 2024
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y1LriIK38pV3lBCLv2M9vynHoyXTFco3BqTUGUEjbDnCeAQYFgoAKgUCUdDGgAkQ
xircDd0e3XMWIQSy6bUy1VvWKH7HnhfGKtwN3R7dcwIbDAAA8PEA/16fgmhfrX12
GXFXcTGO8MKQTihxz2djD4aki7fVX+ZAAP9UT/A3jAfqvFNp+ecYkkZ8T+vnXR4P
0O22blDNAr/tDA==
=q5En
-----END PGP PRIVATE KEY BLOCK-----
Here is the corresponding Public Key consisting of:
* A v4 Ed25519 Public-Key packet
* A User ID packet
* A v4 positive certification self-signature
* A v4 ECDH (Curve25519) Public-Subkey packet
* A v4 subkey binding signature
* A v4 ML-KEM-ipd-768 + X25519 Public-Subkey packet
* A v4 subkey binding signature
Kousidis, et al. Expires 5 September 2024 [Page 54]
Internet-Draft PQC in OpenPGP March 2024
-----BEGIN PGP PUBLIC KEY BLOCK-----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=dPFW
-----END PGP PUBLIC KEY BLOCK-----
Here is an SEIPDv1 unsigned message "Testing\n" encrypted to this
key:
* A v3 PKESK
* A v1 SEIPD
Kousidis, et al. Expires 5 September 2024 [Page 55]
Internet-Draft PQC in OpenPGP March 2024
The hex-encoded KMAC eccKeyShare input is
ba6634c5bab5756868dac8282054b0b30916d764e1f15841222392e5545a67c7.
The hex-encoded KMAC mlkemKeyShare input is
a6b263da0e367b39c2d44bf4c3f66015f410ee4fa674ddbba8d50cde2fc4094a.
The hex-encoded KMAC256 output is
504bc329627af248947117936bee9e87230d327d5c5f5b4db593c4b58b2d0339.
The hex-encoded session key is
b639d5feaae6c8eabcf04182322d576298193cfa9555d869cf911ffbbc5e52e7.
-----BEGIN PGP MESSAGE-----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=h3Km
-----END PGP MESSAGE-----
Here is an SEIPDv2 unsigned message testing encrypted to this key:
* A v6 PKESK
* A v2 SEIPD
Kousidis, et al. Expires 5 September 2024 [Page 56]
Internet-Draft PQC in OpenPGP March 2024
The hex-encoded KMAC eccKeyShare input is
50a74bfb94dc7677bc02f278eb4e7d5d2f1b04e34a2b5c7b8da0579f3e1e0825.
The hex-encoded KMAC mlkemKeyShare input is
161911216c93a5b7936f9a8876c446b0767c904c94786bfc79bcc505b45f5075.
The hex-encoded KMAC256 output is
ee4dacbc4efac509ad5f79640d5963af038baf512d55974c46ac71db6c1ed579.
The hex-encoded session key is
27e3c564fa7b8adb7ee1cfede3ee2cda79dd8f1a6d029ebeb7f3880c752185f6.
-----BEGIN PGP MESSAGE-----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-----END PGP MESSAGE-----
Acknowledgments
Thanks to Daniel Huigens and Evangelos Karatsiolis for the early
review and feedback on this document.
Kousidis, et al. Expires 5 September 2024 [Page 57]
Internet-Draft PQC in OpenPGP March 2024
Authors' Addresses
Stavros Kousidis
BSI
Germany
Email: stavros.kousidis@bsi.bund.de
Johannes Roth
MTG AG
Germany
Email: johannes.roth@mtg.de
Falko Strenzke
MTG AG
Germany
Email: falko.strenzke@mtg.de
Aron Wussler
Proton AG
Switzerland
Email: aron@wussler.it
Kousidis, et al. Expires 5 September 2024 [Page 58]
