Authenticator and authentication method

An authenticator for an apparatus with a variable location for authenticating a person at said apparatus according to a given user registered therewith, comprising:

• a biometric authentication device for comparing first biometric information retrieved from said person with second biometric information of said given user stored in storage, to authenticate said person by way of said given user if degree of matching between said first and second biometric information is equal to or higher than a predetermined threshold;
• a location information retriever for retrieving first location information of a first location of said apparatus upon retrieval of said first biometric information, and second location information of a second location of said apparatus before or after retrieving said first location at a predetermined time;
• a movement detector for detecting whether travel of said apparatus occurs upon retrieval of said first biometric information according to said first and second location information;
• a log database unit for storing information of said travel and said first location information in response to authentication of said person;
• a threshold determining unit for determining said threshold by reading from said log database unit.