Provided is a biometric authentication system capable of preventing spoofing attacks even if leakage of key information and a registration conversion template occurs. A communication terminal device (300) calculates secret key information k′ which is exclusive OR of key information k of the registration biological information and masked value c′ which is randomly selected from a predetermined error correction code group, and calculates verified information c′″ which is exclusive OR of sent information c″ and value c′. A biometric authentication device (500) calculates exclusive OR of authentication biological information, information k′, and registration conversion template w, as information c″, wherein the template w is exclusive OR of information x, information k, and authentication parameter c randomly selected from the code group; and performs biometric authentication on the basis of a degree of matching between information c′″ corresponding to information c″, and the parameter c.