Patent ID: 8856899

Claim:
A non-transitory computer-readable storage medium having computer-executable instructions thereon implementing a method performed by a security service for determining whether to grant a user access to a resource, the method comprising: receiving from the user a security term associated with the user, the received security term being in an obscured form derived from a revealed form of the security term according to a predefined padding scheme known to the user and to the security service; retrieving the revealed security term for the user and the padding scheme from a record for the user; applying the retrieved padding scheme to the received obscured security term to result in a de-padded security term; comparing the de-padded security term to the retrieved revealed security term to confirm that the de-padded security term matches the retrieved revealed security term; confirming that the received obscured security term has not been previously employed within a predetermined frame of reference based on a maintained list of security terms associated with the user that have been received during the predetermined frame of reference, whereby if the received obscured security term is purloined and re-used within the predetermined frame of reference, the security service denies access to the resource, wherein the predetermined frame of reference includes a predetermined period of time and a predetermined number of times; and removing the received obscured security term from the maintained list of received obscured security terms associated with the user if the received obscured security term was not received within the predetermined period of time and the predetermined number of times.