Use of Composite ML-DSA in TLS 1.3
draft-reddy-tls-composite-mldsa-01
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Tirumaleswar Reddy.K , Tim Hollebeek , John Gray , Scott Fluhrer | ||
| Last updated | 2024-11-25 | ||
| Replaces | draft-tls-reddy-composite-mldsa | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
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| Stream | Stream state | (No stream defined) | |
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draft-reddy-tls-composite-mldsa-01
TLS T. Reddy
Internet-Draft Nokia
Intended status: Standards Track T. Hollebeek
Expires: 30 May 2025 DigiCert
J. Gray
Entrust
S. Fluhrer
Cisco Systems
26 November 2024
Use of Composite ML-DSA in TLS 1.3
draft-reddy-tls-composite-mldsa-01
Abstract
This document specifies how the post-quantum signature scheme ML-DSA
[FIPS204], in combination with traditional algorithms RSA-
PKCS#1v1.5,RSA-PSS, ECDSA, Ed25519, and Ed448 can be used for
authentication in TLS 1.3. The composite ML-DSA approach is
beneficial in deployments where operators seek additional protection
against potential breaks or catastrophic bugs in ML-DSA.
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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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 30 May 2025.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions and Terminology . . . . . . . . . . . . . . . 3
2. ML-DSA SignatureSchemes Types . . . . . . . . . . . . . . . . 4
3. Signature Algorithm Restrictions . . . . . . . . . . . . . . 5
4. Selection Criteria for Composite Signature Algorithms . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. Restricting Composite Signature Algorithms to the
signature_algorithms_cert Extension . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 8
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
The advent of quantum computing poses a significant threat to current
cryptographic systems. Traditional cryptographic algorithms such as
RSA, Diffie-Hellman, DSA, and their elliptic curve variants are
vulnerable to quantum attacks. During the transition to post-quantum
cryptography (PQC), there is considerable uncertainty regarding the
robustness of both existing and new cryptographic algorithms. While
we can no longer fully trust traditional cryptography, we also cannot
immediately place complete trust in post-quantum replacements until
they have undergone extensive scrutiny and real-world testing to
uncover and rectify potential implementation flaws.
Unlike previous migrations between cryptographic algorithms, the
decision of when to migrate and which algorithms to adopt is far from
straightforward. Even after the migration period, it may be
advantageous for an entity's cryptographic identity to incorporate
multiple public-key algorithms to enhance security.
Cautious implementers may opt to combine cryptographic algorithms in
such a way that an attacker would need to break all of them
simultaneously to compromise the protected data. These mechanisms
are referred to as Post-Quantum/Traditional (PQ/T) Hybrids
[I-D.ietf-pquip-pqt-hybrid-terminology].
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Certain jurisdictions are already recommending or mandating that PQC
lattice schemes be used exclusively within a PQ/T hybrid framework.
The use of Composite scheme provides a straightforward implementation
of hybrid solutions compatible with (and advocated by) some
governments and cybersecurity agencies [BSI2021].
ML-DSA [FIPS204] is a post-quantum signature schemes standardised by
NIST. It is a module-lattice based scheme.
This memo specifies how a composite ML-DSA can be negotiated for
authentication in TLS 1.3 via the "signature_algorithms" and
"signature_algorithms_cert" extensions. Hybrid signatures provide
additional safety by ensuring protection even if vulnerabilities are
discovered in one of the constituent algorithms. For deployments
that cannot easily tweak configuration or effectively enable/disable
algorithms, a composite signature combining PQC signature algorithm
with an traditional signature algorithm offers the most viable
solution.
The rationale for this approach is based on the limitations of
fallback strategies. For example, if a traditional signature system
is compromised, reverting to a PQC signature algorithm would prevent
attackers from forging new signatures that are no longer accepted.
However, such a fallback process leaves systems exposed until the
transition to the PQC signature algorithm is complete, which can be
slow in many environments. In contrast, using hybrid signatures from
the start mitigates this issue, offering robust protection and
encouraging faster adoption of PQC.
Further, zero-day vulnerabilities, where an exploit is discovered and
used before the vulnerability is publicly disclosed, highlights this
risk. The time required to disclose such attacks and for
organizations to reactively switch to alternative algorithms can
leave systems critically exposed. By the time a secure fallback is
implemented, attackers may have already caused irreparable damage.
Adopting hybrid signatures preemptively helps mitigate this window of
vulnerability, ensuring resilience even in the face of unforeseen
threats.
1.1. Conventions and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. These words may also appear in this
document in lower case as plain English words, absent their normative
meanings.
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This document is consistent with the terminology defined in
[I-D.ietf-pquip-pqt-hybrid-terminology]. It defines composites as:
_Composite Cryptographic Element_: A cryptographic element that
incorporates multiple component cryptographic elements of the same
type in a multi-algorithm scheme.
2. ML-DSA SignatureSchemes Types
As defined in [RFC8446], the SignatureScheme namespace is used for
the negotiation of signature scheme for authentication via the
"signature_algorithms" and "signature_algorithms_cert" extensions.
This document adds new SignatureSchemes types for the composite ML-
DSA as follows.
enum {
mldsa44_ecdsa_secp256r1_sha256 (0x0907),
mldsa65_ecdsa_secp384r1_sha384 (0x0908),
mldsa87_ecdsa_secp384r1_sha384 (0x0909),
mldsa44_ed25519 (0x090A),
mldsa65_ed25519 (0x090B),
mldsa44_rsa2048_pkcs1_sha256 (0x090C),
mldsa65_rsa3072_pkcs1_sha256 (0x090D),
mldsa65_rsa4096_pkcs1_sha384 (0x090E),
mldsa44_rsa2048_pss_pss_sha256 (0x090F),
mldsa65_rsa3072_pss_pss_sha256 (0x0910),
mldsa65_rsa4096_pss_pss_sha384 (0x0911),
mldsa87_ed448 (0x0912)
} SignatureScheme
Each entry specifies a unique combination of an ML-DSA parameter, an
elliptic curve or RSA variant, and a hashing function. The first
algorithm corresponds to ML-DSA-44, ML-DSA-65, and ML-DSA-87, as
defined in [FIPS204]. It is important to note that the mldsa*
entries represent the pure versions of these algorithms and should
not be confused with prehashed variants, such as HashML-DSA-44, also
defined in [FIPS204]. Support for prehashed variants is not required
because TLS computes the hash of the message (e.g., the transcript of
the TLS handshake) that needs to be signed.
In TLS, the data used for generating a digital signature is unique
for each TLS session, as it includes the entire handshake. Thus, ML-
DSA can utilize the deterministic version. The context parameter
defined in [FIPS204] Algorithm 2/Algorithm 3 MUST be an empty string.
The signature MUST be computed and verified as specified in
Section 4.4.3 of [RFC8446]. The Composite-ML-DSA.Sign function,
defined in [I-D.ietf-lamps-pq-composite-sigs], will be utilized by
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the sender to compute the signature field of the CertificateVerify
message. Conversely, the Composite-ML-DSA.Verify function, also
defined in [I-D.ietf-lamps-pq-composite-sigs], will be employed by
the receiver to verify the signature field of the CertificateVerify
message.
Note: In the LAMPS WG, it is being discussed that the composite
signature API should avoid using protocol-specific encoding.
The corresponding end-entity certificate when negotiated MUST use the
First AlgorithmID and Second AlgorithmID respectively as defined in
[I-D.ietf-lamps-pq-composite-sigs].
The schemes defined in this document MUST NOT be used in TLS 1.2
[RFC5246]. A peer that receives ServerKeyExchange or
CertificateVerify message in a TLS 1.2 connection with schemes
defined in this document MUST abort the connection with an
illegal_parameter alert.
3. Signature Algorithm Restrictions
TLS 1.3 removed support for RSASSA-PKCS1-v1_5 [RFC8017] in
CertificateVerify messages, opting for RSASSA-PSS instead.
Similarly, this document restricts the use of the composite signature
algorithms mldsa44_rsa2048_pkcs1_sha256,
mldsa65_rsa3072_pkcs1_sha256, and mldsa65_rsa4096_pkcs1_sha384
algorithms to the "signature_algorithms_cert" extension. These
composite signature algorithms MUST NOT be used with the
"signature_algorithms" extension. These values refer solely to
signatures which appear in certificates (see Section 4.4.2.2 of
[RFC8446]) and are not defined for use in signed TLS handshake
messages.
A peer that receives a CertificateVerify message indicating the use
of the RSASSA-PKCS1-v1_5 algorithm as one of the component signature
algorithms MUST terminate the connection with a fatal
illegal_parameter alert.
4. Selection Criteria for Composite Signature Algorithms
The composite signatures specified in the document are restricted set
of cryptographic pairs, chosen from the intersection of two sources:
* The composite algorithm combinations as recommended in
[I-D.ietf-lamps-pq-composite-sigs], which specify both PQC and
traditional signature algorithms.
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* The mandatory-to-support or recommended traditional signature
algorithms listed in TLS 1.3.
By limiting algorithm combinations to those defined in both
[I-D.ietf-lamps-pq-composite-sigs] and TLS 1.3, this specification
ensures that each pair:
* Meets established security standards for composite signatures in a
post-quantum context, as described in
[I-D.ietf-lamps-pq-composite-sigs].
* Is compatible with traditional digital signatures recommended in
TLS 1.3, ensuring interoperability and ease of adoption within the
TLS ecosystem.
This conservative approach reduces the risk of selecting unsafe or
incompatible configurations, promoting security by requiring only
trusted and well-vetted pairs. Future updates to this specification
may introduce additional algorithm pairs as standards evolve, subject
to similar vetting and inclusion criteria.
5. Security Considerations
The security considerations discussed in Section 11 of
[I-D.ietf-lamps-pq-composite-sigs] needs to be taken into account.
6. IANA Considerations
This document requests new entries to the TLS SignatureScheme
registry, according to the procedures in Section 6 of [TLSIANA].
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+======+================================+=============+===========+
|Value | Description | Recommended | Reference |
+======+================================+=============+===========+
|0x0907| mldsa44_ecdsa_secp256r1_sha256 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x0908| mldsa65_ecdsa_secp384r1_sha384 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x0909| mldsa87_ecdsa_secp384r1_sha384 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x090A| mldsa44_ed25519 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x090B| mldsa65_ed25519 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x090C| mldsa44_rsa2048_pkcs1_sha256 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x090D| mldsa65_rsa3072_pkcs1_sha256 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x090E| mldsa65_rsa4096_pkcs1_sha384 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x090F| mldsa44_rsa2048_pss_pss_sha256 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x0910| mldsa65_rsa3072_pss_pss_sha256 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x0911| mldsa65_rsa4096_pss_pss_sha384 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
|0x0912| mldsa87_ed448 | N | This |
| | | | document. |
+------+--------------------------------+-------------+-----------+
Table 1
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6.1. Restricting Composite Signature Algorithms to the
signature_algorithms_cert Extension
IANA is requested to add a footnote indicating that the
mldsa44_rsa2048_pkcs1_sha256, mldsa65_rsa3072_pkcs1_sha256, and
mldsa65_rsa4096_pkcs1_sha384 algorithms are defined exclusively for
use with the signature_algorithms_cert extension and are not intended
for use with the signature_algorithms extension.
7. References
7.1. Normative References
[I-D.ietf-lamps-pq-composite-sigs]
Ounsworth, M., Gray, J., Pala, M., Klaußner, J., and S.
Fluhrer, "Composite ML-DSA For use in X.509 Public Key
Infrastructure and CMS", Work in Progress, Internet-Draft,
draft-ietf-lamps-pq-composite-sigs-03, 21 October 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-lamps-
pq-composite-sigs-03>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/rfc/rfc8446>.
[TLSIANA] Salowey, J. A. and S. Turner, "IANA Registry Updates for
TLS and DTLS", Work in Progress, Internet-Draft, draft-
ietf-tls-rfc8447bis-10, 3 November 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-tls-
rfc8447bis-10>.
7.2. Informative References
[BSI2021] Federal Office for Information Security (BSI), "Quantum-
safe cryptography - fundamentals, current developments and
recommendations", October 2021,
<https://www.bsi.bund.de/SharedDocs/Downloads/EN/BSI/
Publications/Brochure/quantum-safe-cryptography.pdf>.
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[FIPS204] "FIPS-204: Module-Lattice-Based Digital Signature
Standard", <https://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.204.pdf>.
[I-D.ietf-pquip-pqt-hybrid-terminology]
D, F., P, M., and B. Hale, "Terminology for Post-Quantum
Traditional Hybrid Schemes", Work in Progress, Internet-
Draft, draft-ietf-pquip-pqt-hybrid-terminology-04, 10
September 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-pquip-pqt-hybrid-terminology-04>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/rfc/rfc5246>.
[RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
"PKCS #1: RSA Cryptography Specifications Version 2.2",
RFC 8017, DOI 10.17487/RFC8017, November 2016,
<https://www.rfc-editor.org/rfc/rfc8017>.
Acknowledgments
Thanks to Bas Westerbaan, Alicja Kario, Ilari Liusvaara and Sean
Turner for the discussion and comments.
Authors' Addresses
Tirumaleswar Reddy
Nokia
Bangalore
Karnataka
India
Email: kondtir@gmail.com
Timothy Hollebeek
DigiCert
Pittsburgh,
United States of America
Email: tim.hollebeek@digicert.com
John Gray
Entrust Limited
2500 Solandt Road – Suite 100
Ottawa, Ontario K2K 3G5
Canada
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Email: john.gray@entrust.com
Scott Fluhrer
Cisco Systems
Email: sfluhrer@cisco.com
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