elliptic

Facts and the checks behind them

Nothing below is copied from documentation. The check content/libraries/verify/elliptic/run.sh ran elliptic 6.6.1 on Node.js 24.22.0 in the container image node:24.22.0-bookworm-slim on October 20, 2026; the page must match what it printed, and each fact lists those lines.

• ECDSA signature encoding

  structured

  sign() returns an object with r, s and recoveryParam; toDER() produces ASN.1 DER, and raw r‖s has to be assembled from the two values padded to the curve size.

  Recorded by the check

  fact ecdsa-signature-encoding = structured
  evidence ecdsa-signature-encoding: sign() returns an object with r, s and recoveryParam 0; toDER() gives 72 bytes that parse as DER: true

• What the signing call hashes

  takes-digest

  The input to sign() and verify() is used as the digest; signing the raw message produced a different signature than signing its SHA-256.

  Recorded by the check

  fact ecdsa-prehash = takes-digest

• ECDSA nonce

  rfc6979

  RFC 6979 with HMAC-DRBG: the P-256 test vector from appendix A.2.5 reproduced exactly, including its high s.

  Recorded by the check

  fact ecdsa-nonce = rfc6979
  evidence ecdsa-nonce: r and s equal RFC 6979 A.2.5 (high s kept): true

• Nonces that differ from RFC 6979

  P-521/SHA-512

  On P-521 with SHA-512, 9 of 2,048 fixed inputs used a nonce different from RFC 6979 (the reference was @noble/curves); no difference showed on secp256k1/SHA-256 or P-256/SHA-512 in 4,096 inputs each. This matches advisory GHSA-848j-6mx2-7j84, open for all versions up to 6.6.1.

  Recorded by the check

  fact rfc6979-divergence = P-521/SHA-512
  evidence rfc6979-divergence: secp256k1 with SHA-256, 4096 fixed inputs: 0 nonces differ from RFC 6979, 0 of those signatures still verify
  evidence rfc6979-divergence: P-256 with SHA-512, 4096 fixed inputs: 0 nonces differ from RFC 6979, 0 of those signatures still verify
  evidence rfc6979-divergence: P-521 with SHA-512, 2048 fixed inputs: 9 nonces differ from RFC 6979, 9 of those signatures still verify

• Low-S when signing

  either

  Not normalized by default: the RFC test vector came back with its high s. canonical: true returns n − s instead.

  Recorded by the check

  fact ecdsa-low-s-sign = either
  evidence ecdsa-low-s-sign: canonical: true returns n - s: true

• High-S when verifying

  accepts-high-s

  Both the high-S and the low-S form of the same signature verified.

  Recorded by the check

  fact ecdsa-low-s-verify = accepts-high-s
  evidence ecdsa-low-s-verify: the RFC signature (high s) and its low-s twin both verify: true

• DER strictness

  rejects-non-minimal

  A DER signature whose r carried a redundant leading zero was refused with Signature without r or s, while the minimal encoding from toDER() verified.

  Recorded by the check

  fact der-strictness = rejects-non-minimal
  evidence der-strictness: the minimal DER from toDER() verifies when passed back as bytes: true
  evidence der-strictness: non-minimal INTEGER encoding: throws Signature without r or s

• Malformed ECDSA signature

  throws

  A 64-byte raw r‖s blob or a 3-byte array passed to verify() throws Signature without r or s instead of returning false.

  Recorded by the check

  fact ecdsa-malformed-signature = throws
  evidence ecdsa-malformed-signature: 64-byte raw r||s: throws Signature without r or s
  evidence ecdsa-malformed-signature: 3 bytes: throws Signature without r or s

• ECDSA curves

  P-224P-256P-384P-521secp256k1

  P-224, P-256, P-384, P-521 and secp256k1 signed and verified; there are no Brainpool curves.

  Recorded by the check

  fact ecdsa-curves = P-224, P-256, P-384, P-521, secp256k1

• EdDSA

  Ed25519

  Ed25519 through new elliptic.eddsa("ed25519").

  Recorded by the check

  fact eddsa = Ed25519

• Post-quantum algorithms

  none

  No post-quantum algorithms.

  Recorded by the check

  fact pqc = none

• Public key formats

  sec1-uncompressedsec1-compressed

  keyFromPublic() read hex SEC1 points, compressed or uncompressed, and an object of hex x and y coordinates; a 64-byte x‖y without the 0x04 prefix was refused.

  Recorded by the check

  fact public-key-formats = sec1-uncompressed, sec1-compressed
  evidence public-key-formats: an object of hex x and y coordinates also works: true; there is no PEM, SPKI, PKCS#8 or JWK parser

• Private key formats

  raw-scalar

  Private keys are the raw scalar as hex or bytes; there is no PEM, PKCS#8 or JWK parser.

  Recorded by the check

  fact private-key-formats = raw-scalar

Usage

import { createHash } from "node:crypto";
import elliptic from "elliptic";

const ec = new elliptic.ec("secp256k1");
const key = ec.genKeyPair();

// elliptic signs exactly the bytes it is given: hash the message yourself,
// and pass bytes — never a string.
const digest = createHash("sha256").update("order #1042 approved").digest();

// canonical: true keeps s in the lower half, which Bitcoin and noble verifiers require.
const signature = key.sign(digest, { canonical: true });

const der = Buffer.from(signature.toDER());
const raw = Buffer.concat([signature.r.toArrayLike(Buffer, "be", 32), signature.s.toArrayLike(Buffer, "be", 32)]);
console.log("low-S:", signature.s.cmp(ec.nh) <= 0);
console.log("verified:", key.verify(digest, der), "raw bytes:", raw.length);