Abstract
Because the conventional test architectures are mainly designed to increase the controllability and observability of the signals, they are identified as potential sources of attacks when implemented in systems dealing with digital security. It is then necessary to develop appropriate test methods.
This thesis presents test solutions for encryption systems focusing on both tests performed at the end of production or maintenance, and tests carried out during the mission mode.
Regarding off-line tests performed after production or in-situ, the approach relies on an integrated self-test schemes. It presents the combined advantages of limiting the access to internal data, and thus preserves data security, conducting a test of high quality, thus it guarantees the proper system behavior, and finally requiring only very little additional resources. Taking advantage of inherent properties of encryption algorithms (diffusion, confusion, iteration) and their physical implementations (feedback architectures), self-test solutions are proposed for DES and AES cores. It is also demonstrated how such crypto-cores can be used as test resources for other cores in the system.
Regarding the tests performed during the functional mode, the proposed approach allows the detection of faults using different forms of duplication (information or hardware redundancies).