algovoi-rfc9421-ecdsa

ECDSA (P-256 / P-384) add-on for the AlgoVoi RFC 9421 verifier.

A pure add-on: it does not modify or re-publish the core verifier. It gives you a drop-in verify_request that accepts Ed25519 (delegated verbatim to the untouched verifier) plus the two RFC 9421-registered ECDSA suites:

• ecdsa-p256-sha256 (RFC 9421 3.3.5): P-256, SHA-256, 64-byte r‖s signature
• ecdsa-p384-sha384 (RFC 9421 3.3.6): P-384, SHA-384, 96-byte r‖s signature

The ECDSA path reuses the verifier's already-hardened primitives (Signature-Input parsing, freshness/replay, Content-Digest, signing-base, downgrade/allow-list) and adds only the ECDSA signature check. The core verifier stays Ed25519 + PyNaCl-only and unchanged; this package brings its own cryptography dependency.

from algovoi_rfc9421_ecdsa import verify_request

result = verify_request(
    method="POST", authority="api.example.com", path="/a2a",
    headers=headers, body=body, public_key=sec1_point_bytes,
    allowed_algorithms={"ecdsa-p256-sha256"},   # opt in per request
)
# Ed25519 requests are delegated to the core verifier automatically.

Hardening

Before accepting an ECDSA signature the provider enforces:

• the public-key point is on the curve and not the identity;
• the signature is exactly the curve size (64 / 96 bytes, raw r‖s, not DER);
• r and s are each in [1, n-1];
• optional canonical low-s enforcement (anti-malleability) via set_strict_low_s(True), off by default for spec interop.

Apache-2.0.