Image Number 5 for United States Patent #8099771.
It is possible to issue an IC card storing unique encryption key information in such a manner that re-issuing is enabled and sufficient security can be assured. An IC card provider X delivers an IC card having a group code G(A) to a company A and an IC card having a group code G(B) to a company B. When a company staff .alpha. inputs a unique personal code P(.alpha.) and performs initialization, in the IC card, calculation is performed according to a predetermined algorithm using the P(.alpha.) and G(A). Data uniquely determined by the calculation is stored as encryption key information K(.alpha.) in the IC card. Even if the company staff .alpha. loses the IC card, it is possible to obtain the IC card having the same encryption key information K(.alpha.) as before by performing initialization again by using the IC card delivered by the IC card provider X.