def encrypt(fingerprint, data):
    """
    Encrypts the given data known the fingerprint to be used
    in the way Telegram requires us to do so (sha1(data) + data + padding)

    :param fingerprint: the fingerprint of the RSA key.
    :param data: the data to be encrypted.
    :return:
        the cipher text, or None if no key matching this fingerprint is found.
    """
    global _server_keys
    key = _server_keys.get(fingerprint, None)
    if not key:
        return None

    # len(sha1.digest) is always 20, so we're left with 255 - 20 - x padding
    to_encrypt = sha1(data).digest() + data + os.urandom(235 - len(data))

    # rsa module rsa.encrypt adds 11 bits for padding which we don't want
    # rsa module uses rsa.transform.bytes2int(to_encrypt), easier way:
    payload = int.from_bytes(to_encrypt, 'big')
    encrypted = rsa.core.encrypt_int(payload, key.e, key.n)
    # rsa module uses transform.int2bytes(encrypted, keylength), easier:
    block = encrypted.to_bytes(256, 'big')
    return block