Yes good point - I might be able to make that work if I spent the time to perfect it, but I'm not a security guy so there was the off chance I might overlook something.
There were couple other good reasons for the signup given my initial target demographic of two people :). And you may have also noticed that everyone gets an Elo rating if you visit /spielers.html
As a side project I weighed the options and just chose to have signups rather than complicate the issue. They can be purely anonymous, and it makes it easier for me to manage. If it is really a stopping point for losing potential players I am willing to live with that.
On a side note - I'm very glad to see you are enjoying the game. You've played almost as many games as me in 1/100th the time!
Can you please elaborate on why you believe signup is necessary to prevent cheating?