Scrypt for Python
==

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There are a lot of different scrypt modules for Python, but none of them have
everything that I'd like, so here's One More[1].


Features
--
* Uses hashlib.scrypt on Python 3.6 and OpenSSL 1.1.
* Uses system libscrypt[2] as the next choice.
* If neither is available, tries the scrypt Python module[3] or libsodium[4].
* Offers a pure Python scrypt implementation for when there is no C scrypt.
* Not unusably slow, even in pure Python... at least with pypy[5].

With PyPy as the interpreter the Python implementation is around one fifth the
speed of C scrypt. With CPython it is between about 50x and 250x slower.


Requirements
--
* Python 2.7.8+ or 3.4+. Equivalent versions of PyPy should also work.
* If you want speed, you should use one of:
  - libscrypt 1.8+ (older may work)
  - py-scrypt 0.6+ (pip install scrypt)
  - libsodium 1.0+
  - Python 3.6+ with OpenSSL 1.1+


Usage
--

You can install the most recent release from PyPi using:

    pip install pylibscrypt

You most likely want to create MCF hashes and store them somewhere, then check
user-entered passwords against those hashes. For that you only need to use two
functions from the API:

    from pylibscrypt import scrypt_mcf, scrypt_mcf_check
    # Generate an MCF hash with random salt
    mcf = scrypt_mcf(b'Hello World')
    # Test it
    print(scrypt_mcf_check(mcf, b'Hello World'))   # prints True
    print(scrypt_mcf_check(mcf, b'HelloPyWorld'))  # prints False

For full API, you can try help(pylibscrypt) from python after importing.

It is highly recommended that you use a random salt, i.e. don't pass one.


Versioning
--
The package has a version number that can be read from python like so:

    print(pylibscrypt.__version__)

The version number is of the form X.Y.Z, following Semantic Versioning[6].
Releases are tagged vX.Y.Z and release branches bX.Y.x when they differ from
master.


Development
--
Development happens on GitHub[7]. If you find a bug, please open an issue there.

Running pylibscrypt.tests will test all implementations with some quick tests.
Running any implementation directly (e.g. pylibscrypt.pylibsodium) will also
compare to scrypt test vectors from the paper but this is slow for the pure
Python version (pypyscrypt) unless running with pypy.

You can test more comprehensively using the docker test environment. Either
build and run using `make docker-run` or pull the jvarho/pylibscrypt image and
run using `docker run -v ${PWD}:/app jvarho/pylibscrypt`.

Pull requests should be automatically tested and will not be merged if broken.

[1]:https://xkcd.com/927/
[2]:https://github.com/technion/libscrypt
[3]:https://bitbucket.org/mhallin/py-scrypt/src
[4]:https://github.com/jedisct1/libsodium
[5]:http://pypy.org/
[6]:http://semver.org/spec/v2.0.0.html
[7]:https://github.com/jvarho/pylibscrypt

