Procedures for securing programmes and checking the integrity of secured programmes.

摘要

To protect the programs contained in a system memory and to check their integrity, the programs are in each case coded in accordance with a symmetric cryptographic algorithm, by using a secret key which is stored protected against reading and during this process a test number is formed for each program and is stored in the system memory. For the integrity check, the programs are then again coded in the same manner and the test number obtained in each case during this process is compared with the test number stored during the first coding process. From the result of the comparison, a criterion can be derived for activating or blocking subsequent programs. IMAGE