Patent ID: 7284133

Claim:
An information processing unit, comprising: a calculation equipment; first and second memory devices; a first bus line that links the calculation equipment and the first memory device; and a second bus line that links the calculation equipment and the second memory device; wherein the calculation equipment receives first key data stored in the first memory device through the first bus line, wherein the calculation equipment encrypts input data using the first key data and stores the encrypted data in the second memory device, wherein the calculation equipment reads out the encrypted data from the second memory device, re-encrypts the encrypted data using second key data without the decryption of the encrypted data and stores the re-encrypted data in the second memory device, wherein the calculation equipment reads out the re-encrypted data from the second memory device and decrypts the re-encrypted data using third key data generated from the first and second key data, wherein the input data is separated into a plurality of blocks and each block is encrypted using the first and second key data and decrypted using the third key data, and further wherein the execution order of encryption/decryption processing of the sequence of blocks is randomly changed with an execution order control data which is stored in a memory.