| Internet-Draft | ML-DSA for SSH | October 2025 |
| Petrov | Expires 11 April 2026 | [Page] |
This document describes the use of the ML-DSA digital signature algorithms in the Secure Shell (SSH) protocol. Accordingly, this RFC updates RFC 4253.¶
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Secure Shell (SSH) [RFC4251] is a secure remote-login protocol. It provides for an extensible variety of public key algorithms for identifying servers and users to one another.¶
This document describes the use of ML-DSA algorithms to be implemented by Secure Shells (SSH) and standardize the use of names "ssh-mldsa-44", "ssh-mldsa-65", and "ssh-mldsa-87". Those algorithms correspond to the Table 1. "ML-DSA parameter sets" defined in [FIPS-204] Section 4 "Parameter Sets".¶
The descriptions of key and signature formats use the notation introduced in [RFC4251], Section 3 and the string data type from [RFC4251], Section 5.¶
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.¶
This document describes a public key algorithms for use with SSH, as per [RFC4253], Section 6.6. The name of the algorithms are "ssh-mldsa-44", "ssh-mldsa-65", and "ssh-mldsa-87". Those algorithms only supports signing and not encryption. Keys are generated according to the procedure described in [FIPS-204] Algorithm 1 step 5.¶
Standard implementations of SSH SHOULDimplement "ssh-mldsa-65" signature algorithm. It MAY implement "ssh-mldsa-44" and "ssh-mldsa-87" signature algorithms.¶
The "ssh-mldsa-44" key format has the following encoding:¶
Here, 'key' is the 1312-octet public key encoded as is described in [FIPS-204] Algorithm 22.¶
The "ssh-mldsa-65" key format has the following encoding:¶
Here, 'key' is the 1952-octet public key encoded as is described in [FIPS-204] Algorithm 22.¶
The "ssh-mldsa-87" key format has the following encoding:¶
Here, 'key' is the 2592-octet public key encoded as is described in [FIPS-204] Algorithm 22.¶
Signatures are generated according to the procedure described in [FIPS-204]. Signature generation should use normal signing process (Pure ML-DSA Signature Generation) with empty string as context parameter. The process is defined in [FIPS-204] Algorithm 2 step 10(sign) and Algorithm 3 step 5(verify).¶
The "ssh-mldsa-44" public key algorithm has the following format for encoding the signature:¶
Here, 'signature' is the 2420-octet signature produced in accordance with [FIPS-204] Algorithm 2.¶
The "ssh-mldsa-65" public key algorithm has the following format for encoding the signature:¶
Here, 'signature' is the 3309-octet signature produced in accordance with [FIPS-204] Algorithm 2.¶
The "ssh-mldsa-87" public key algorithm has the following format for encoding the signature:¶
Here, 'signature' is the 4627-octet signature produced in accordance with [FIPS-204] Algorithm 2.¶
ML-DSA signatures are verified according to the procedure in [FIPS-204] Algorithm 3 step 5.¶
This document augments the Public Key Algorithm Names in [RFC4250], Section 4.11.3.¶
This document requests new entries to "Public Key Algorithm Names" in the "Secure Shell (SSH) Protocol Parameters" registry [IANA-SSH] according to the procedures in [RFC9519], Section 3:¶
| Public Key Algorithm Name | Reference |
|---|---|
| ssh-mldsa-44 | This document. |
| ssh-mldsa-65 | This document. |
| ssh-mldsa-87 | This document. |
The security considerations in [RFC4251], Section 9 apply to all SSH implementations, including those using ML-DSA-44, ML-DSA-65, and ML-DSA-87.¶
TBD: post-quantum security considerations ...¶
TBD¶