Patent ID: 8340361

Claim:
A biometric authentication system comprising: a database holding enrolled feature data with respect to each of enrolled users u n (n=1 to N); each time biometric data is inputted from a claimant v, a feature extraction unit for extracting feature data of the claimant v based on the biometric data acquired from the claimant v; a prior probability setting unit for setting prior probabilities of the enrolled users u n and a prior probability of a non-enrolled user u 0 ; a 1:N matching unit for performing 1:N matching between the extracted claimant feature data of the claimant and the enrolled feature data held in the database and calculating a matching score of each of the enrolled users u n ; a likelihood ratio calculation unit for calculating a ratio of the likelihood v=u n to the likelihood v≠u n with respect to each of the enrolled users u n , by using the calculated matching scores according to input times of the biometric data; a posterior probability calculation unit for calculating posterior probabilities of the enrolled users u n and a posterior probability of the non-enrolled user u 0 , using the calculated likelihood ratios, the prior probabilities of the enrolled users u n , and the prior probability of the non-enrolled user u 0 ; and a determination unit for comparing each of the calculated posterior probabilities with a first threshold, when a maximum value of the posterior probability is larger than the first threshold, and when the posterior probability showing the maximum value is one of the posterior probabilities of the enrolled users u n , determining that the corresponding enrolled user and the claimant v are identical, while when the posterior probability showing the maximum value is the posterior probability of the non-enrolled user u 0 , determining that the claimant v is a non-enrolled user u 0 , when the maximum value of the posterior probability is equal to or less than the first threshold, and when the number of acquisitions of the biometric data from the claimant v is less than a predetermined value, requesting to reacquire the biometric data of the claimant v, and while when the number of acquisitions is equal to or more than the predetermined value, determining “authentication failure”.