diff --git a/draft-miller-sshm-composite-sigs.xml b/draft-miller-sshm-composite-sigs.xml index 1abb403..e3f1e82 100644 --- a/draft-miller-sshm-composite-sigs.xml +++ b/draft-miller-sshm-composite-sigs.xml @@ -491,14 +491,32 @@ apply here. - The security of this composite scheme depends on the strength of - both component algorithms. An adversary must break both ML-DSA - and the Elliptic Curve algorithm to forge a signature. + The security of this composite scheme depends on the security of both + component algorithms. An adversary must forge both ML-DSA and Elliptic Curve + signatures in order to forge a composite signature. Implementations MUST NOT reuse component key material between composite and non-composite keys, or between multiple composite - keys. + keys. See section 9.3. + + + If neither of the component algorithms are broken, both + ssh-mldsa44-ed25519 and ssh-mldsa87-p384 are Existentially Unforgeable under + Chosen-Message Attack (EUF-CMA), since ML-DSA, Ed25519, and ECDSA are all + EUF-CMA and SHA-512 is collision-resistant. If one of the component + algorithms are broken. See + section 9.2.1. + + + This composite scheme is not Strongly Unforgeable under Chosen-Message + Attack (SUF-CMA). Systems that rely on this property SHOULD NOT use this + scheme. + + + This composite scheme provides Weak Non-Separability (WNS) for both + components due to evidence of the composite in the Prefix in `M'`. See + section 9.2.3.