The Croatian Ruder Boskovic Institute proposes the services of a quantum random bit generator. We often insisted on the importance of high randomness in secure protocols.
But this institute has also find an extremely “funny” why to limit the access to its service to a limited set of knowledgeable people with its captcha. Captcha is a set of technique that attempts to discriminate humans trying to sign in from automatic machines. It usually requests people to dial in a set of characters which readability has been decreased. The Institute succeeded to discriminate between different categories of human. It requires to solve mathematical problems (and not simple arithmetic calculus ). Definitively, not a place to sign in after an exhausting day.
Have a look at the registration page, and look for several challenges.