The brief of design is as follow 1. Create independent module to generate Random numbers (now this is choice how much typical random number you want). Ideally this should be a static call which when call return random number that's it. 2. you can have choice indicator in as config param to return number as TEXT or image (however image would need more complexities and resource centric) Now the Important process is 1. Whenever you send captcha to client, store the same as hidden field in form so that when client submit you can validate using Javascript or you can send the hidden to server and validate on server too. Other options are you can store that in cookie and revalidate on server and rewrite new captcha to cookie if requested new one.