PHP Captcha without session

Question

Ok, here is an issue: in the project i\'m working on, we can\'t rely on server-side sessions for any functionality.

The problem is that common captcha solutions fro

Answer 1

Can you grant them a client certificate in response to a CAPTCHA call? Then once they select that certificate in the browser it's sent with each call from the client, and can be used for authentication without sessions and without further CAPTCHA calls.