def crypto_box_keypair():
    """
    Returns a randomly generated public and secret key.

    :rtype: (bytes(public_key), bytes(secret_key))
    """
    pk = ffi.new("unsigned char[]", crypto_box_PUBLICKEYBYTES)
    sk = ffi.new("unsigned char[]", crypto_box_SECRETKEYBYTES)

    rc = lib.crypto_box_keypair(pk, sk)
    ensure(rc == 0,
           'Unexpected library error',
           raising=exc.RuntimeError)

    return (
        ffi.buffer(pk, crypto_box_PUBLICKEYBYTES)[:],
        ffi.buffer(sk, crypto_box_SECRETKEYBYTES)[:],
    )
Returns a randomly generated public and secret key.

    :rtype: (bytes(public_key), bytes(secret_key))