You have to store something in order to provide a secure captcha. If you don't store anything, a malicious user agent could always return the same combination of text and encrypted data, and it would always pass.

You could limit that with timestamps, but then you force all legitimate users to respond in a timely fashion - not a good idea.

In reply to Re^5: need suggestions on Perl modules to support Encrypt Data by moritz
in thread need suggestions on Perl modules to support Encrypt Data by lihao

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