c# - What's the best strategy for having multiple captcha image at the same time? -

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let me explain problem giving example: imagine creating blog application in users can leave comments, need ensure if user human or not. keep in mind due limitations, can't use google recaptcha, have create own captcha code.

so far there no problem since there bunch of samples on internet , of them use sessions keep last created code , of them use encrypted key, in url or hidden input in forms.

firstly, if use sessions i'm not able display several blog posts contain unique captcha code can validate them after user submission because keep last generated random code.

secondly, if use encrypted key , reveal in output html or in query string easy robots use generated key several times unless store these keys after submission. if choose use disposable keys have search database every time prevent generating duplicated random code.

the question what's best approach let users open several posts , leave comment each 1 less code , i/o complexity.


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