Efficient implementation of the XTEA encryption algorithm.

Author: Kevin Turner (kevin@ksturner.com)
License: GPL v3

DISCLAIMER:
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This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.

IF YOU READ ONE THING IN HERE, READ THIS
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This module has been compiled and tested under Python 2.5 and 2.6, but not
Python 3.

This package provides a C-based implementation of the XTEA block encryption
algorithm (http://www.cix.co.uk/~klockstone/xtea.pdf). It is very similar to
the Python implementation of the XTEA algorithm by Paul Chakravarti 
(http://code.activestate.com/recipes/496737/), but is suitable for encrypting
large amounts of data fast.

The module implements the basic XTEA block encryption algortithm function which
symmetrically encrypts/decrypts a variable length string using XTEA in OFB mode
as a key generator. 

This module is intended to provide a simple, but very fast, 'privacy-grade'
Python encryption algorithm with no external dependencies. Note that the XTEA
algorithm has not been subjected to extensive analysis (though is believed to
be relatively secure - see http://en.wikipedia.org/wiki/XTEA). For applications
requiring 'real' security please use a known and well tested
algorithm/implementation.

The security of the algorithm is entirely based on quality (entropy) and
secrecy of the key. You should generate the key from a known random source and
exchange using a trusted mechanism. In addition, you should always use a random
IV to seed the key generator (the IV is not sensitive and does not need to be
exchanged securely)


There is an example.py script that demonstrates basic use of the xtea2 package
by encrypting and decrypting files. (see python example.py --help)