viem

Facts and the checks behind them

Nothing below is copied from documentation. The check content/libraries/verify/viem/run.sh ran viem 2.57.7 on Node.js 24.22.0; viem depends on @noble/curves 1.9.1 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

  rsv-65

  signMessage() returns 65 bytes as hex: r, s and v.

  Recorded by the check

  fact ecdsa-signature-encoding = rsv-65

• Recovery id v

  27-28

  v is 27 or 28; parseSignature() also reports it as yParity 0 or 1.

  Recorded by the check

  fact recovery-v = 27-28

• Message prefix

  eip-191

  hashMessage() equals keccak-256 of the EIP-191 prefix, the decimal length and the message, computed independently.

  Recorded by the check

  fact message-prefix = eip-191

• Default hash

  keccak256

  Message signatures use keccak-256.

  Recorded by the check

  fact ecdsa-default-hash = keccak256

• What the signing call hashes

  hashes-message-or-digest

  signMessage() hashes with the EIP-191 prefix; sign() with a hash parameter signs a 32-byte digest unchanged and produced the identical signature for that digest.

  Recorded by the check

  fact ecdsa-prehash = hashes-message-or-digest
  evidence ecdsa-prehash: sign() over the EIP-191 digest equals signMessage(): true

• ECDSA nonce

  rfc6979

  RFC 6979: the signature matched @noble/curves' deterministic signature over the same digest.

  Recorded by the check

  fact ecdsa-nonce = rfc6979

• Low-S when signing

  low-s

  No high-S value among 64 message signatures.

  Recorded by the check

  fact ecdsa-low-s-sign = low-s

• High-S when verifying

  accepts-high-s

  The mirrored signature (r, n − s) with v flipped recovered the signer in recoverMessageAddress() and verified in the verifyMessage utility.

  Recorded by the check

  fact ecdsa-low-s-verify = accepts-high-s
  evidence ecdsa-low-s-verify: recoverMessageAddress with (r, n - s, flipped v): recovers the signer

• Signature shapes accepted

  v-27-28v-0-1

  65-byte signatures with v = 27/28 or v = 0/1 recovered the signer; the 64-byte EIP-2098 form failed with invalid signature length.

  Recorded by the check

  fact signature-input-shapes = v-27-28, v-0-1
  evidence signature-input-shapes: v-27-28: recovers the signer
  evidence signature-input-shapes: v-0-1: recovers the signer
  evidence signature-input-shapes: eip-2098: invalid signature length
  evidence signature-input-shapes: verifyMessage utility, high-S twin: true
  evidence signature-input-shapes: verifyMessage utility, eip-2098: invalid signature length
  evidence signature-input-shapes: eip-2098 expanded with parseCompactSignature and compactSignatureToSignature: recovers the signer
  evidence signature-input-shapes: parseSignature returns v 28 and yParity 1

• ECDSA curves

  secp256k1

  secp256k1 only.

  Recorded by the check

  fact ecdsa-curves = secp256k1

• EdDSA

  none

  No EdDSA.

  Recorded by the check

  fact eddsa = none

• Post-quantum algorithms

  none

  No post-quantum algorithms.

  Recorded by the check

  fact pqc = none

• Public key formats

  sec1-uncompressed

  account.publicKey is the 65-byte uncompressed SEC1 point.

  Recorded by the check

  fact public-key-formats = sec1-uncompressed
  evidence public-key-formats: account.publicKey is 65 bytes starting with 0x04: true

Usage

import { recoverMessageAddress, verifyMessage } from "viem";
import { generatePrivateKey, privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(generatePrivateKey());
const message = "Sign in to example.com\nNonce: 8f2c1a";

// EIP-191 personal_sign, RFC 6979, low-S, v = 27 or 28.
const signature = await account.signMessage({ message });

// For EOAs this is ecrecover plus an address comparison; for smart-contract
// wallets use the publicClient.verifyMessage action, which also checks ERC-1271.
const valid = await verifyMessage({ address: account.address, message, signature });
const signer = await recoverMessageAddress({ message, signature });

console.log("signature bytes:", (signature.length - 2) / 2);
console.log("valid:", valid, "signer matches:", signer === account.address);