Patent ID: 7278029

Claim:
A program writable IC card comprising: a first memory which stores a first program having a decryption function, wherein said first memory is a read only memory (ROM) which is not re-writable; a second memory which stores a second program; an input unit which inputs an encrypted second program from outside the IC card; and a microprocessor which, upon input of said encrypted second program by said input unit, determines whether said encrypted second program has been encrypted correctly, and if said encrypted second program has been encrypted correctly, processes said encrypted second program after said encrypted second program has been input by said input unit, wherein said microprocessor, upon execution of said first program after said encrypted second program has been determined to have been encrypted correctly, applies said decryption function to said encrypted second program and then writes a decrypted second program, which is executable by said microprocessor, in said second memory, and wherein, when said encrypted second program is not encrypted correctly, writing of said encrypted second program into said second memory is rejected.