geesefly.py is a pure Python implementation of the Skein hash function and Threefish tweakable block cipher. It also includes a pseudo-random number generator based on Skein, and Cipher-Block Chaining (CBC) based functionality for encrypting variable-length data. geesefly.py is slow. If you want a high-performance Python implementation of Skein and Threefish, I highly recommend PySkein, available at http://packages.python.org/pyskein/ In PySkein, the heavy lifting is done in compiled C, and hashes data at a much faster rate than geesefly.py. In contrast, this module is written in pure Python. While slow, it is useful for applications where compiling a Python C extension is unfeasible, such as Google's App Engine. You also may find the geesefly.py code helpful in understanding Skein and Threefish. geesefly.py works with Python version 2.5 or later. This includes version 3 and up. Skein is a hash function submitted to NIST for their cryptographic hash algorithm competition. Skein is designed by Niels Ferguson, Stefan Lucks, Bruce Schneier, Doug Whiting, Mihir Bellare, Tadayoshi Kohno, Jon Callas, and Jesse Walker More information is available at http://www.skein-hash.info/