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ECDSA Signature Parser

Parse ECDSA signatures into r, s, v components

r: The x-coordinate of a random point on the elliptic curve (32 bytes)

s: The signature proof value (32 bytes)

v: Recovery ID that helps recover the public key (1 byte, optional)

Common v values:

  • 27 or 28: Legacy Ethereum signatures
  • 0 or 1: Modern EIP-2098 compact signatures
  • 35+: EIP-155 signatures with chain ID

1. What is an ECDSA signature?

ECDSA (Elliptic Curve Digital Signature Algorithm) signatures are used in Ethereum to prove ownership of an address. A signature consists of three components: r, s, and optionally v.

2. How does it work?

ECDSA uses elliptic curve mathematics to create signatures. The signer generates a random point on the curve (r coordinate), then uses their private key and message hash to compute s. The v value (recovery ID) helps recover the public key from the signature. Ethereum uses the secp256k1 curve for this process.

Signature formats

Ethereum signatures can be in two formats:

  • 65 bytes (130 hex): r (32) + s (32) + v (1) - Standard format with recovery ID
  • 64 bytes (128 hex): r (32) + s (32) - Compact format without v

Recovery ID (v)

The v value helps recover the public key from the signature:

  • 27/28: Original Ethereum (pre-EIP-155)
  • 0/1: EIP-2098 compact signatures
  • 35+: EIP-155 with chain ID protection

Formula for EIP-155: v = chainId * 2 + 35 + yParity

3. Examples

Standard 65-byte signature

0x + 64 hex chars (r) + 64 hex chars (s) + 2 hex chars (v) = 130 total

Compact 64-byte signature

0x + 64 hex chars (r) + 64 hex chars (s) = 128 total

Legacy v values

v = 27 (0x1b) or v = 28 (0x1c) for pre-EIP-155 signatures

References