File: cast128.txt

CAST 128 Encryption/Decryption Class
By Devin Doucette
Copyright (c) 2004 Devin Doucette
Email: darksnoopy@shaw.ca

As the name implies, this is an implementation of the CAST128 algorithm. 
Obviously it isn't very fast since it's written in PHP, but I did my best to improve the 
speed.  It's ideal for encrypting *SMALL* text and files, don't expect it to encrypt or 
decrypt large files without bogging down your server.  Using base64 encoding on the 
encrypted data usually makes it easier to store in cookies, session variables, etc.

The class itself is fairly simple, as there are only four functions that you would ever 
need to call.  These are as follows:

Creating an object is fairly straightforward.
$example = new cast128;

Set the key using the setkey function:
$example->setkey("Your key, whatever it may be");

Encrypt data using the encrypt function:
Takes the data to be encrypted as the first argument, and optionally a key as the second. 
If no key is provided it will use the last key that was set, either through the encrypt or 
decrypt functions or through the setkey function.
$example->encrypt("This is the text/data to be encrypted");
$example->encrypt("This is the text/data to be encrypted", "MYKEY");

Decrypt data using the decrypt function:
Takes the data to be decrypted as the first argument, and optionally a key as the second. 
If no key is provided it will use the last key that was set, either through the encrypt or 
decrypt functions or through the setkey function.
$example->decrypt($data);
$example->decrypt($data, "MYKEY");

Run a test to ensure that the script is working properly:
Uses known values to ensure that the script is able to implement that CAST128 algorithm.
$example->test();
Returns true if it succeeded, false if it failed.