Patent ID: 7721107
Filing Date: 2010-05-18
Classification: G06F

Abstract:
1. A computer implemented method for verifying human presence in an online environment, the method comprising: issuing a challenge from a first computational unit to a second computational unit after the second computational unit communicates a request to access a service provided by the first computational unit; computing at a third computational unit a response using a function that takes as input a synchronization measure and a symmetric key shared with the first computational unit; the computed response being computed for satisfying the challenge issued by the first computational unit to the second computational unit; displaying the computed response on a user interface of the third computational unit only if interaction instructions involving a physical challenge output on the user interface are satisfied; receiving input at the second computational unit representing the computed response displayed on the user interface of the third computational unit; transmitting the input received representing said computed response from the second computational unit to the first computational unit for satisfying the challenge issued by the first computational unit; authenticating, at the first computational unit, the computed response received from the second computational unit using a function that takes as input the computed response and the symmetric key shared with the third computational unit; and enabling, at the first computational unit, access to the service to the second computational unit in response to authenticating the computed response received from the second computational unit; wherein said computing computes the computed response at the third computational unit with a symmetric cipher that takes as input a measure of time at the third computational unit and the symmetric key shared with the first computational unit; wherein said enabling deciphers ciphertext received from the second computational unit using a symmetric cipher that takes as input the ciphertext and the symmetric key shared with the third computational unit.