Encoding and Decoding a string to Base64 for QueryStrings

A friend of mine asked me today about encoding a string Base64. The scenario was that he has some files that he wants to be allowed for download on their company website and that he doesn't want the people who are downloading the files from his website to see where the downloads are coming from. The files are located in a folder inside the webserver outside of the virtual directory. The decision that the came up with was just to Base64 encode all the paths, pass ito to a new page via querystring and then decode that value on the download page. I gave it a shot and this is the code i gave him to serve as a guide on how he can effectively implement this.