Circuit with safety measures against complicate spying on the circuit

摘要

Circuit comprises a computer unit (12) and a number of intermediate memories (14) for storing intermediate results. The computer is designed to read and or write intermediate results from the intermediate memory. A monitoring device (18) is provided for checking the security of the circuit, which loads a test pattern into the intermediate memory and then reads it out again. A testing element of the monitoring device checks the data read out with the test written to the intermediate memory. If there is a discrepancy an alarm signal is generate and appropriate measures triggered. An Independent claim is made for a method for operating a circuit with a computer unit and intermediate memory in order to detect changes in data in intermediate memory.