padding.py 文件源码

def calculate_max_pss_salt_length(key, hash_algorithm):
    if not isinstance(key, (rsa.RSAPrivateKey, rsa.RSAPublicKey)):
        raise TypeError("key must be an RSA public or private key")
    # bit length - 1 per RFC 3447
    emlen = int(math.ceil((key.key_size - 1) / 8.0))
    salt_length = emlen - hash_algorithm.digest_size - 2
    assert salt_length >= 0
    return salt_length