ENCRIPTION OF ADDRESSED INFORMATION STREAM TO BE USED FOR PROTECTING PROGRAM CODE

摘要

PURPOSE: To protect the private information stored in the physical memory of a computer or an algorithm. CONSTITUTION: An encrypting method selecting certain bytes of the data stored within a specified on-chip memory 21 as encrypting keys is provided. These selected bytes are used for encrypting themselves and all the remaining data within the specified memory. the selected bytes do not have the values especially assigned for the encryption and they are simply selected from the main body of data to be encrypted in accordance with a prescribed rule. When this technique is enforced, each byte of the data stored in the memory is coupled with one of the encrypting key bytes designated before a disclosure (for instance, by using an exclusive NOR gate). A user separately supplies a pair of key bytes and is not required to perform a program or to take a safe measure.