Ed25519 verification uses permissive `verify` instead of `verify_strict`

[ckeshava]

Description

Ed25519 signature verification calls ed25519_dalek::VerifyingKey::verify rather than the stricter verify_strict. verify_strict rejects malleable/non-canonical encodings and torsion-point edge cases documented in RFC 8032 §8.4. Permissive verification can accept signatures that rippled rejects (or vice versa).

Location

• src/core/keypairs/algorithms.rs#L456-L484

Impact / Severity

Medium — Consensus divergence. A client that accepts signatures rippled rejects (or vice versa) will disagree on transaction validity, with downstream effects on hashing, relaying, and confirmation logic.

Adversarial Agent Notes

Verdict: ACCEPT. Call site uses value.verify(...) — the dalek 2.x docs explicitly call this permissive.

[satyakwok]

Fix submitted in #301.

Single-line change: value.verify(...) → value.verify_strict(...) inside Ed25519::is_valid_message. All existing keypair tests (13 sign/verify round-trips across Ed25519 and secp256k1) still pass.