A cryptographic nonce is important for confirming that a party is active and fully participating in a protocol exchange. One reason attackers can succeed with many web-page attacks is that it is relatively easy to craft authentic-looking pages that spoof actual sites. Suggest a technique by which a user can be assured that a page is both live and authentic from a particular site. That is, design a mark, data interchange, or some other device that shows the authenticity of a web page.

What will be an ideal response?

The key to this question is that the page give the user information that a spoofer could not have predicted in advance. This could mean information about the user that only the true site would know (e.g., last login time) or some sort of interactivity requirement through a separate channel (e.g., an ID number the sitesent the user in the mail).