DATA PROTECTING MICROCOMPUTER

摘要

PURPOSE:To protect the data on a microcomputer by adding a logic circuit for ciphers between a processor and a built-in memory in a single-chip microcomputer so that the data outside the processor is ciphered. CONSTITUTION:The data ciphered by a specific ciphering key is recorded in a nonvolatile program data area 106. While the specific ciphering key supplied from a terminal 101 via an I/O terminal 102 and a decoding key are recorded into a volatile memory 103. The data supplied from the terminal 101 via the terminal 102 is ciphered by a ciphering logic circuit 104 and ciphered by means of the key recorded in the memory 103. This ciphered data is stored into a memory 107. When the data is processed by a CPU 105, a normal sentence is supplied as it is and a built-in memory and the recorded data are decoded by the circuit 104. Then the decoded normal sentence is supplied to the CPU 105.