Security - Turing test

not visible input not used named email (but for accessibility, a message that say "this field not used")

ReCAPATCHA v2

http://www.google.com/recaptcha/api2/demo http://www.w3.org/WAI/PF/wiki/CAPTCHA_v2 https://stackoverflow.com/questions/25545514/how-does-this-checkbox-recaptcha-work-and-how-can-i-use-it http://googlesystem.blogspot.fr/2014/12/no-captcha-recaptcha.html