def xor_encrypt(plaintext: str, key: int) -> str:
    """ Encrypt a plaintext into a hex-encoded ciphertext.

    Args:
        plaintext (str): The plaintext to encrypt
        key (int): The single-byte key

    Returns:
        str: The hex-encoded ciphertext
    """
    return bytes(ord(c) ^ key for c in plaintext).hex()