How to verify an ECDSA signature in Node.js

1import { readFileSync } from "node:fs";
2import { createPublicKey, verify } from "node:crypto";
3 
4const publicKey = createPublicKey(readFileSync("pub.pem")); // SPKI PEM
5const message = readFileSync("message.txt");
6const signature = readFileSync("sig.der"); // ASN.1 DER, 70-72 bytes on P-256
7 
8const ok = verify("sha256", message, publicKey, signature);
9console.log(ok ? "valid" : "INVALID");

1const okRaw = verify(
2  "sha256",
3  message,
4  { key: publicKey, dsaEncoding: "ieee-p1363" },
5  readFileSync("sig.raw"), // r‖s, exactly 64 bytes on P-256
6);
7console.log(okRaw ? "valid" : "INVALID");

How it works

1. createPublicKey accepts an SPKI PEM (-----BEGIN PUBLIC KEY-----) directly; DER and JWK work too via an options object.
2. verify("sha256", …) hashes the message for you — pass the original message bytes, never a pre-computed digest.
3. The default signature format is ASN.1 DER. For raw r‖s signatures, wrap the key as { key, dsaEncoding: "ieee-p1363" }.
4. verify returns a boolean for a wrong signature; it only throws on malformed keys or unsupported parameters.

Gotchas

• A 64-byte signature fails against the DER default, and a DER signature fails once ieee-p1363 is set. Check signature.length first: 64/96/132 means raw, ~70 starting with 0x30 means DER.
• The hash must match the signer exactly — verifying a SHA-384 signature with "sha256" yields false with no further diagnostics.
• If verification keeps failing with inputs you believe are right, suspect encodings before keys: base64 vs base64url of the signature, or a UTF-8 vs hex reading of the message.

Related recipes

• How to sign a message with ECDSA in Node.js
• How to convert an ECDSA signature between DER and raw in Node.js
• How to verify an ES256 JWT in Node.js