I agree with hardburn.
What I use is taken from Lincoln Stein's Apache Modules book. I create a string which is passed to the cookie and is also saved in a database for comparison.
It might be overkill but the cookie string is updated on each page as one of the fields used to create it is a timestamp. As Lincoln points out this is extremely sensitive to the smallest change in passed parameters, therefore is very hard to spoof and (almost) insures randomness.

use MD5;
my $MAC = MD5->hexhash( $secret.
MD5->hexhash(join '', $secret, @fields)
);
[download]

The $secret variable holds a 128 character string, which should be as random as possible.
The @fields array holds whatever data you want to use, as stated before preferably not relevant user data, which combination should of course be unique for each session.
Changing the $secret string on a regular basis will also provide peace of mind ;-)

Update

use MD5;
my $MAC = MD5->hexhash( $secret.
MD5->hexhash(join ':', $secret, @fields)
);
[download]

It looks like the book had a typo as this correct version of the code appears somewhere else in the book.
Sorry Lincoln, my bad!

jayrom

---

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.