Increasing the Effective Volume of Digital Watermark Used in Monitoring the Program Code Integrity of FPGA-Based Systems

Abstract

The paper deals with monitoring the program code integrity of FPGA-based systems. An approach to the integrity monitoring considered in the paper is based on embedding the digital watermark into the information object of FPGA chips program code. A digital watermark, which is embedded into the program code, contains a monitoring hash sum. Such kind of embedding does not change the program code size and operation of device, which is programmed with the help of this program code. In using this approach the integrity monitoring is provided by the condition that the digital watermark extraction and the recovery of initial state of program code information object occur simultaneously. In the paper a method, which allows increasing the embedded digital watermark effective volume, is proposed. Increasing the effective volume of the digital watermark gives the possibility to use a broader set of hash functions to monitoring the integrity. This allows using the hash functions possessing a big cryptographically strong in the process of the integrity monitoring. Increasing the effective volume is achieved due to the preliminary preparation of the FPGA program code information object, which (preparation)is performed before the embedding of digital watermark. In the course of this preparation the information object bits set by the embedding key are led to some predetermined state. In the paper an experimental research of the proposed method efficiency in the point of increasing the effective volume of the digital watermark is presented.