Patent ID: 7730520
Filing Date: 2010-06-01
Classification: G06F,G07C,G10L

Abstract:
1. A method using an interactive computer for verifying the identity of a claimant attempting to access a resource comprising the steps of: providing a trusted database containing information of multiple identifiers for each identity where the identifiers are partitioned into multiple groups and identifiers in the same group are correlated and identifiers in different groups are not correlated; selecting one at a time the identifier that approximately provides the largest expected decrease in the ratio of the joint probability of responses of an impostor to the joint probability of responses of a legitimate claimant per unit cost; and computing by means of an interactive computer joint probabilities of responses for a legitimate claimant and for an impostor using equations where K is a set of identifiers, K g is a set of identifiers in group g, PO r (K g ) is the joint probability that an ignorant impostor claiming identity r would provide responses as specified by a set of identifiers K g , Q r (K g ) is the joint probability that a legitimate claimant of identity r would provide responses as specified by a set of identifiers K g , PIO r (k=outcome) is the input estimate of the probability that an ignorant impostor claiming identity r would respond with an outcome response to identifier k where outcome could be a match, no-match, or ambiguous response, PL r (k=outcome) is the input estimate of the probability that a legitimate claimant for identity r would respond with an outcome response to identifier k, P r (K) is the joint probability that a random (ignorant or well-informed) impostor claiming identity r would provide responses as specified by a set of identifiers K, and PI r (k =outcome |K) is the conditional probability that a random (ignorant or well-informed) impostor claiming identity r would respond with an outcome response to identifier k ∉ K, given that the session so far has produced the responses of the identifiers in the set K; determining, using the computed joint probabilities, whether the claimant can be accepted or rejected while guaranteeing that an impostor is accepted with a probability that does not exceed a first specified parameter α and a legitimate claimant is rejected with a probability that does not exceed a second specified parameter β using inequalities p re-computing by means of the interactive computer conditional probabilities of an impostor using where PI r (k=outcome|K g ) is the conditional probability that a random (ignorant or well-informed) impostor claiming identity r would respond with an outcome response to identifier k ∉ K g in group g, given that the session so far has produced the responses of the identifiers in the set K g , and φ g is the input estimate of the probability that an impostor finds trusted information of the identifiers in group g, which make the responses as good as those of a legitimate claimant, and selecting a new identifier or granting access or denying access or terminating the session inconclusively.