crypto.py 文件源码

def verify_hmac(expected_result, secret_key, unique_prefix, data):
    '''
    Perform a HMAC using the secret key, unique hash prefix, and data, and
    verify that the result of:
    HMAC-SHA256(secret_key, unique_prefix | data)
    matches the bytes in expected_result.
    The key must be kept secret. The prefix ensures hash uniqueness.
    Returns True if the signature matches, and False if it does not.
    '''
    # If the secret key is shorter than the digest size, security is reduced
    assert secret_key
    assert len(secret_key) >= CryptoHash.digest_size
    h = hmac.HMAC(bytes(secret_key), CryptoHash(), backend=default_backend())
    h.update(bytes(unique_prefix))
    h.update(bytes(data))
    try:
        h.verify(bytes(expected_result))
        return True
    except InvalidSignature:
        return False