def eth_sign_sha3(data: bytes) -> bytes:
    """
    eth_sign/recover compatible hasher
    Prefixes data with "\x19Ethereum Signed Message:\n<len(data)>"
    """
    prefix = b'\x19Ethereum Signed Message:\n'
    if not data.startswith(prefix):
        data = prefix + b'%d%s' % (len(data), data)
    return keccak(data)