title: Software evaluation licensing
body: <p>My company is looking to start distributing some software we developed and would like to be able to let people try the software out before buying.  We'd also like to make sure it can't be copied and distributed to our customers' customers.</p>
  
  <p>One model we've seen is tying a license to a MAC address so the software will only work on one machine.</p>
  
  <p>What I'm wondering is, what's a good way to generate a license key with different information embedded in it such as license expiration date, MAC address, and different software restrictions?</p>