Patent ID: 8595813

Claim:
An IC card, used for executing an encryption process or a decryption process using unique encryption key information, said IC card comprising: a memory; a CPU that executes predetermined processes based on data and programs stored in the memory; and an I/O unit that performs transaction of information with an exterior; a first storage location, a second storage location, and a third storage location being secured inside said memory; said programs including a basic program, a key information generating program and an encryption and decryption program; said basic program having a function of carrying out a first process of writing provided data to be written as a non-rewritable fixed code into said first storage location, when a write command with data to be written into said first storage location is provided from the exterior via said I/O unit, and a function of carrying out a second process of writing provided data to be written as a rewritable variable code into said second storage location, when a write command with data to be written into said second storage location is provided from the exterior via said I/O unit; said key information generating program having a function of carrying out a computation process based on a predetermined algorithm using the non-rewritable fixed code stored in said first storage location and the rewritable variable code stored in said second storage location to generate encryption key information that is determined uniquely according to said non-rewritable fixed code and rewritable variable code and storing the encryption key information in said third storage location, when a key information generating command is provided from the exterior via said I/O unit; and said encryption and decryption program having a function of carrying out an encryption process or a decryption process inside the IC card using the encryption key information stored in said third storage location, when a command for an encryption process or a command for a decryption process is provided from the exterior via I/O unit; wherein the first process is enabled only once and a predetermined fixed code has already been written in the first storage location as said non-rewritable fixed code by carrying out the first process so as to disable rewriting of said predetermined fixed code in the first storage location.