Storing this information in a hidden field is not the best way to handle passing state (think about the security implications). You might want to look into cookies or possibly the Apache::Session module for alternatives. Of course that's not the question you asked.

I would recommend creating an MD5 hash of the username, password, and some other non-related data such as random numbers or the timestamp and using that for authentication purposes. Here's the results from a CPAN search on MD5. MD5::Digest is usually available with any perl distribution with a recent version of the CPAN bundle.

Note that this approach doesn't encrypt the username and password, but instead creates a unique 32 bit string from the data you feed it. If you are adding a timestamp and random data to the string you feed the MD5 algorithm, than a user is not likely (I know better than to say never here) to have the same MD5 hash on two different trips to your site.

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Coyote