add support for mldsa44-ed25519 (draft-miller-sshm-composite-sigs) - #583
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quexten wants to merge 3 commits into
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add support for mldsa44-ed25519 (draft-miller-sshm-composite-sigs)#583quexten wants to merge 3 commits into
quexten wants to merge 3 commits into
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quexten
commented
Aug 28, 2026
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| The lethargic, colorless dog sat beneath the energetic, stationary fox. No newline at end of file | |||
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quexten
commented
Aug 28, 2026
| let mldsa_sig = | ||
| ml_dsa::Signature::<MlDsa44>::try_from(mldsa_sig).map_err(|_| Error::Signature)?; | ||
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| if !VerifyingKey::<MlDsa44>::decode(&mldsa_pk).verify_with_context(&m_prime, LABEL, &mldsa_sig) |
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Is this okay? Or should we verify both sigs first, then do a const time comparison of the results?
quexten
commented
Aug 28, 2026
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| let mldsa_sig = mldsa_signing_key(sk) | ||
| .expanded_key() | ||
| .sign_deterministic(&m_prime, LABEL) |
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The ML-DSA and Ed25519 signatures are calculated as:
mldsa_sig = ML-DSA-44.Sign(mldsa_sk, M', ctx=Label)
ed25519_sig = Ed25519.Sign(ed25519_sk, M')
quexten
marked this pull request as ready for review
August 28, 2026 08:42
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Adds support for https://www.ietf.org/archive/id/draft-miller-sshm-composite-sigs-01.html mldsa44-ed25519 composite keys. Given that openssh currently does not have plans to support raw mldsa keys, this superseeds my other PR.
I've tested support for interoperability on
OpenSSH_10.5p1, OpenSSL 3.6.3 9 Jun 2026in SSH agent (I signed and verified a file signature via SSH agent using this PR's implementation).(With some further patches in Bitwarden's SSH Agent):
