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PyNaCl: A Python Wrapper for NaCl


This is a simple wrapper for the NaCl cryptographic library (not Google's NativeClient).


PyNaCl currently wraps the following NaCl functions:

  • crypto_hash_sha256
  • crypto_hash_sha512
  • crypto_randombytes

And the following groups of functions (if not otherwise specified by the suffix, it just wraps the default primitive):

  • crypto_scalarmult_curve25519
  • crypto_box
  • crypto_sign
  • crypto_secretbox
  • crypto_stream
  • crypto_auth
  • crypto_onetimeauth


The API is a very straightforward translation of NaCl's C API. Any function that returns an error code will raise ValueError if it returns anything but zero. Output arguments are returned, with keypair functions returning 2-tuples and everything else returning strings. The wrapper handles all padding, so you can just ignore that part of NaCl's documentation.

Eventually I'll translate the documentation over, but for now look at and the NaCl documentation.


SWIG is required to generate the wrapper:

apt-get install swig

Download pynacl with the embedded NaCL (verify it's the latest version):

git clone

NaCl does not build with the -fPIC flag and therefore you must modify a file:

cd pynacl/nacl-20110221
sed -i "s/$/ -fPIC/" okcompilers/c*

If you want the build status output printed to screen, you may also do:

sed -i "s/exec 2\?>.*//" do

You can then build NaCl with:


Once NaCl is successfully built, you can run:

cd ../
python build
sudo python install


To run the tests, just run the script "" in the distribution directory.


PyNaCl is released under version 2.0 of the Apache license.

To do

  • Convert to a package so I can add Python code
  • Implement a higher-level API
  • Implement fromseed versions of other key generation functions