@algovoi/rfc9421-ecdsa

ECDSA (P-256 / P-384) add-on for @algovoi/rfc9421-verifier.

A pure add-on: it does not modify or re-publish the core verifier. It gives you a drop-in verifyRequest 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-only and unchanged; this package brings its own @noble/curves dependency.

import { verifyRequest } from "@algovoi/rfc9421-ecdsa";

const result = await verifyRequest({
  method: "POST",
  authority: "api.example.com",
  path: "/a2a",
  headers,
  body,
  publicKey: sec1PointBytes,
  allowedAlgorithms: ["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 setStrictLowS(true), off by default for spec interop.

Byte-for-byte decision parity with the Python algovoi-rfc9421-ecdsa package, verified by a cross-implementation differential. Apache-2.0.