Self-healing systems can restore their original functionality by use of run-time self-reconfiguration, a feature supplied by state of the art FPGA devices. Commonly, integrity checks are performed by reading back the device configuration and validating its hash value. Systems which are prone to tampering and piracy of intellectual property may disable configuration readback, which renders this method infeasible. We propose to secure systems by use of test vectors, requiring a certain system input sequence to always generate the same system output. The presented security mechanism is hard to tamper with and does not interfere with normal system operation. Although the required hardware overhead may be high in general, we show that the overhead can be kept relatively low if the method is applied only to select parts of the system, without any detrimental effect to the level of security that our mechanism provides. The mechanism is introduced into VHDL code using an automatic process. This approach to self-test and self-healing has been implemented on a Xilinx Virtex-5 device.
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