A disc stores therein a computer program and encrypted information. A BIOS is executed at the time of start-up and starts the computer program. A TPM is connected to the BIOS by a low-speed bus. The TPM includes a register for storing data. A blob stores therein true hash values of the computer program and the BIOS in advance. The BIOS includes a hash value calculating unit that calculates hash values of the computer program and the BIOS and stores those hash values in the register. The TPM compares the hash values stored in the register with the hash values stored in the blob and decrypts information in the blob if the hash values agree with each other.