IDENTITY VERIFICATION SYSTEM

An input pattern of an individual requesting identity verification, such as a speech pattern, is compared with reference patterns of a plurality of categories in a category recognition unit to recognize the category of the input pattern. A differential pattern corresponding to a difference between the input pattern and the reference pattern of the same category as that of the input pattern is computed by a differential pattern computation unit. The differential pattern is verified, in a verification unit, against reference differential patterns registered in a verification data file to perform the identity verification. When the identity verification based on the differential pattern is difficult, a feature vector pattern distinctively representing a feature of the individual is extracted from the differential pattern. The feature vector pattern is verified, by the verification unit, against reference feature vector pattern data of the same category registered in the verification data file.