Data security website

I want a simple website (no great graphics frontend will do - just has to work), based on following specifications. The budget for the project is fixed at 200 USD. If you have the skills to do it at this price then only bid. Here are the details:- A web-based service provider has some confidential information, which has been given access to some agent of the provider. In case the service provider discovers that some of the confidential data from him has ended up in the open internet or unsecured location freely accessible, he can deduce that the data was leaked through one of his agents. Now to detect whether the data was leaked from a particular agent, the provider will check the leaked file for the some data injected for a specific agent that will help track him. I dont want to use electronic watermark which are easy to be altered, but some other method the details of which you can find in the file attached.