Patent ID: 8094890

Claim:
A biometric authentication apparatus for identifying a subject person by using biometric information of a user, comprising: a biometric information sensor for detecting biometric information; a processing unit for executing biometric authentication; and a memory for storing data, wherein: said memory stores a remaining trial number whose value is reduced each time biometric authentication performed by said processing unit fails; said processing unit generates a lower limit value which is random and smaller than a remaining trial number at the start of biometric authentication, executes biometric authentication until the reduced remaining trial number becomes equal to or smaller than said lower limit value, and generates alarm data for alarming said user when the reduced remaining trial number is equal to or smaller than said lower limit value; said memory stores first biometric information of said user, a biometric authentication threshold value which is a reference value to be used when a failure or a success of biometric authentication of said user is judged by a magnitude of a value, and a change detection threshold value which is a reference value to be used when a presence or an absence of a change detection of said first biometric information of said user is judged by a magnitude of a value; and said processing unit acquires second biometric information of said user, compares said first biometric information and the acquired second biometric information to calculate an inconsistency degree quantitatively representative of a difference therebetween, and if the calculated inconsistency degree is smaller than said biometric authentication threshold value and larger than said change detection threshold value, generates notice data for notifying said user of a change detection of said first biometric information.