WARNING: THIS CRYPTOGRAPHIC SOFTWARE IS NOT SECURE. DO NOT USE IT EXCEPT FOR
TESTING AND DEMONSTRATION PURPOSES.

This is a simple zero-knowledge proof protocol for an NP-complete language
written in Sage. The NP-complete language here is quadratic assignment over F_2.
The two agents interact using the message-passing with objects rather than
through an explicit channel.

There are many possible improvements to this software:

* Use a cryptographically secure random number generator instead of the Sage and
Python defaults. Currently the software is insecure because of this.

* Use a channel for interactions instead of object message-passing.

* Quadratic assignment problems that correspond to interesting search problems
usually have a sparse matrixfor the quadratic forms. Taking advantage of this
would make the implementation much more efficient.

* Add a system to translate interesting search problems into QA problems.

* Use a salt when hashing for bit-commitment. Everything's better with salt.

* Don't use the Sage pickling system to marshal values into binary form. That's
just stupid.

* While you're at it, rewrite the whole thing from scratch in a different
programming language.

However, I have decided not to implement any of these features in the forseeable
future.