Verification of a human in the loop 
Identification via the Turing Test

Moni Naor


We propose using a ``Turing Test" in order to verify that a human is the one making a query to a service over the web. Thus, before a request is processed the user should answer as a challenge an instance of a problem chosen so that it is easy for humans to solve but the best known programs fail on a non-negligible fraction of the instances. We discuss several scenarios where such tests are desired and several potential sources for problems instances. We also discuss the application of this idea for combatting junk mail.

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