title: Signing HTML Documents Using PGP or SSL via Web Forms
body: <p>Let’s say I have a contract between two parties published on the Web. I want both parties to be able to sign the contract to show they consent to the terms, the way they would with handwriting in real life. I have seen many TOS agreements online where this is done with just a check box, but I want to go a step further and enable each party to assert that the signature is theirs and not a forgery (somebody else checking the box for them).</p>
  
  <ul>
  <li>Assuming the page is already served via HTTPS  and username/password combos are not an option, which cryptographic technology is best suited for identity validation: PGP, SSL, or something else?</li>
  <li>How might I do this using only HTML and a LAMP server on the other end, in such a way that the process is as automated as possible while still being secure? Code samples are obviously welcome but not necessary; I’m just trying to conceptualize it: do the contents of the contract have to be included in the signature? Do I have the users upload public keys or something? I’m no crypto expert so that’s where I get lost.</li>
  </ul>