secp256k1_sign

On-chain secp256k1 ECDSA signing

Sign a message with the secp256k1 signing precompile at 0x69.

Overview

secp256k1_sign() and async_secp256k1_sign():

• hash the input message with an EIP-191 personal-sign prefix

• sign the hash using the provided private key

• return signature bytes (HexBytes)

Signature

def secp256k1_sign(
    w3: Web3,
    *,
    sk: PrivateKey,
    message: str,
) -> HexBytes

async def async_secp256k1_sign(
    w3: AsyncWeb3,
    *,
    sk: PrivateKey,
    message: str,
) -> HexBytes

Parameters

Parameter	Type	Required	Description
w3	Web3 / AsyncWeb3	Yes	Connected Seismic client
sk	PrivateKey	Yes	32-byte secp256k1 private key
message	str	Yes	Message text to sign

Returns

Type	Description
HexBytes	Signature bytes (r/s plus recovery byte)

Examples

Basic Usage

import os
from seismic_web3 import PrivateKey, create_public_client
from seismic_web3 import precompiles as sp

w3 = create_public_client("https://gcp-1.seismictest.net/rpc")

sk = PrivateKey(os.urandom(32))
sig = sp.secp256k1_sign(w3, sk=sk, message="hello")
print(sig.hex())

Verify Off-Chain

from eth_account import Account
from eth_account.messages import encode_defunct

message = "hello"
sig = sp.secp256k1_sign(w3, sk=sk, message=message)

recovered = Account.recover_message(encode_defunct(text=message), signature=sig)
expected = Account.from_key(bytes(sk)).address
assert recovered == expected

Async Usage

import os
from seismic_web3 import create_async_public_client
from seismic_web3 import PrivateKey
from seismic_web3 import precompiles as sp

async def main():
    w3 = create_async_public_client("https://gcp-1.seismictest.net/rpc")
    sk = PrivateKey(os.urandom(32))
    sig = await sp.async_secp256k1_sign(w3, sk=sk, message="async hello")
    print(sig.hex())

Read Signature Components

r = int.from_bytes(sig[0:32], "big")
s = int.from_bytes(sig[32:64], "big")
v = sig[64] if len(sig) > 64 else None

Hashing Behavior

The SDK hashes with:

from eth_hash.auto import keccak

prefix = f"\x19Ethereum Signed Message:\n{len(message)}".encode()
message_hash = keccak(prefix + message.encode())

Gas Cost

Fixed cost: 3000.

Notes

• message is UTF-8 encoded before hashing/signing.

• Keep private keys out of logs and telemetry.

• The output format is suitable for typical Ethereum signature verification flows.

See Also

• secp256k1 Sign — Precompiles Reference

• PrivateKey

• EIP-191

• ecdh