README

Pcrypt, a multi-party polynomial encryption system.

Installation:

Python version 2.4 or higher must be installed on your system.
Also, the Python Cryptography Toolkit must be installed, you can access it
at the url: http://www.pycrypto.org/.

USAGE: pcrypt.py [OPTIONS] file
     -m <number>           Minimum number of keys required to decrypt file
     -n <number>           Number of keys to generate
     -d <filelist>         Decrypt the file
                           <filelist> is a list of semicolon seperated
                           point files, such as file.p1;file.p2;file.p3
     -o <file>             The file to output to
                           By default, the file will be output to file.pcrypt
                           if encrpyting, and file.pdecrypt if decrypting
     -k <keylength>        The length of the key, must be 16, 24, or 32.
                           Default is 16
     --help                Display a help message

For example, to encrypt this file, with 3 people minimum needed to decrypt it
and 5 points to be generated, run the command:

./pcrypt.py -m 3 -n 5 README

this will create a file called README.pcrypt, as well as five point files, 
README.p1, README.p2 ...

At this point, you would distribute README.pcrypt to everyone, as well as giving
everyone one point file.

In order to decrypt the README.pcrypt file, you need at least 3 point files.
Let's say you have p1, p4, and p5. In order to decrypt the file, run the
command:

./pcrypt.py -d README.p1\;README.p4\;README.p5 README.pcrypt

Note that you need the '\' in front of the ';' in order to escape from the
semicolon being interpereted as a shell specific character. This command will 
create a file called README.pcrypt.pdecrpyt, which will be identical to README.