Method and apparatus for personal identification

In a personal identification system of the type wherein a user is provided with a device generating a unique, time varying, nonpredictable code, with a nonsecret identifying code and with a secret PIN, the nonpredictable code at a given instant and the PIN being provided to a central verification computer to effect verification;

• apparatus for providing improved security for the PIN comprising:
• means for mixing the nonpredictable code generated by the device at a given time with the PIN according to a predetermined algorithm to generate a combined coded value;
• means for separately communicating the nonsecret identifying code and the combined coded value to the central verification computer;
• and
• wherein the central verification computer includes means for utilizing the nonsecret identifying code to retrieve the PIN and generate an appropriate, unique, time varying nonpredictable code for the individual, and means for utilizing the retrieved PIN, appropriate nonpredictable code and the combined coded value in performing a verification operation.