Ah, encoding. If you have used networks, wrote webpages, or software you have experienced the most common methods of encoding already. One useful encoding is Base64. It is a two way algorithm, meaning it can be encrypted and decrypted.
Using Base64 in PHP, Coldfusion, and ASP.NET can be very simple compared to encoding in ASP, Active Server Pages. All encryption is based upon a character or bit replacement. Since all ASCII characters are bits, it's just a means of converting the text to it's ASCII equivilent and encoding the ASCII number.
I have written a nice interface to encode/decode text in Base64 using VBScript functions. There are some nice error traps and clipboard copy of the output. The functions encode/decode files via binary streaming method using FSO, File System Object, but this puts a massive strain on our webserver. Give the online Base64 encoder a whirl, and send me a email if you would like the ASP source code.