crypto.py 文件源码

def kdf_rfc5869_derive(secret_input_bytes, output_len, m_expand=M_EXPAND_NTOR,
                       t_key=T_KEY_NTOR):
    '''
    Return output_len bytes generated from secret_input_bytes using RFC5869
    with HKDF-SHA256.
    There is no equivalent verification function, as only the nonce part of
    the KDF result is verified directly.
    See https://gitweb.torproject.org/torspec.git/tree/tor-spec.txt#n1026
    '''
    hkdf_sha256 = hkdf.HKDF(algorithm=hashes.SHA256(),
                            length=output_len,
                            info=bytes(m_expand),
                            salt=bytes(t_key),
                            backend=backends.default_backend())
    output_bytes = hkdf_sha256.derive(bytes(secret_input_bytes))
    assert len(output_bytes) == output_len
    return bytearray(output_bytes)