To prevent the leakage of secret information by leaving an equipment behind or the like by separately managing a portable information equipment main body and an IC card and to make a user recognize that the IC card is stolen even when it is temporarily stolen and to prevent the leakage of the secret information thereafter by constructing the mechanism of rewriting a secret key on the IC card and a public key inside a portable information equipment every time the IC card is used.

To the portable information equipment main body 1, the IC card 2 is mounted through a card slot 3. In this case, at the time of program activation for accessing a memory storing information to be kept secret or at the time of the activation of the equipment itself, the portable information equipment main body 1 generates random data, sends the data ciphered by using the public key to the IC card 2 and checks the data converted to plane sentences by the secret key and transferred from the IC card 2. Thus, the activation of the program or the boot strap operation of an OS(operating system) is permitted or inhibited.