Use ffi.from_buffer(...) for conversions, so that bytearray, memoryview and other things work too, instead of checking that the arguments are bytes instances.

I would also prefer being able to give output buffers to low level functions, for instance I had to do this hack to enable encryption without creating a new buffer. It works even in place, if ciphertext and message are the same buffer:

from nacl._sodium import ffi, lib def encrypt_into(ciphertext, message, aad, nonce, key): mlen = len(message) clen = ffi.new("unsigned long long *") ciphertext = ffi.from_buffer(ciphertext) message = ffi.from_buffer(message) if aad: _aad = ffi.from_buffer(aad) aalen = len(aad) else: _aad = ffi.NULL aalen = 0 return lib.crypto_aead_chacha20poly1305_ietf_encrypt( ciphertext, clen, message, mlen, _aad, aalen, ffi.NULL, nonce, key )

While for most things it does not matter if copies are made and new buffers are being allocated, stream ciphers can be much faster with proper buffer management.