title: Generating a url that I can use in a sign-off-email
body: <p>So I have a service where you sign up for events. When you sign up, you get an email with an url where you can sign off the event. The given parameter of the url should be something that not anyone can guess. </p>
  
  <p>I've thought of UID, but that just isn't human readable. I also thought of hashing, but I don't know if I want to use that.</p>
  
  <p>btw; I'm doing this in java, in case you know of some nifty tools.</p>
  
  <p>Any suggestions? </p>