Research On Software Watermarking Algorithm

The global financial crisis erupted in 2008 has caused great economic slowdown and recession. But the software industry still keeps steady and rapid growth, which has played an active role in the national economy and society informatization. At the same time, the phenomenon of illegal copy and piracy for software has become a stumbling block to the vigorous development of the software industry, and influenced the protection of the software intellectual property seriously. Thus, the software watermarking based on the technology of software protection has emerged as the times require. Through the establishment of effective real-time inspection and duplicate checking mechanism, the illegal copy and spread of software can be contained to a certain extent by software watermarking.Based on the analysis of the current situation of domestic and foreign software watermarking, two kinds of software watermarking algorithms and a watermarking detecting scheme have been studied and designed in this paper, which all have good features on invisibility and robustness.Firstly, a kind of improved software watermarking algorithm SCC (Selected Color Changing) on register assignment graph coloring has been presented. The watermarking binary is embedded by using the principle of register allocation, constructing the graph coloring model and function and changing the nodes colors in the interfere graph. According to the different numbers between the watermarking binary "0" and "1", the corresponding coloring strategy is selected, which can improve the embedding efficiency and lower the running cost. With the help of the Sandmark platform, the performance analysis of SCC algorithm is completed and the characteristics about resistance, stealth, data-rate, efficiency and cost are elaborated.The software watermarking algorithm based on Hash function SHA-512 is a kind of dynamic watermarking. When selecting the integer constants randomly in the running track of the program and obtaining the message digest using the latest safety standard SHA-512, the logical relationship between watermark message and integer constants is set up. The selected integer constants are replaced by the call function which is constructed, so the watermarking is embedded dynamically. It is hidden in the call function but not data structure, which has stronger robustness. In addition, this algorithm is a blind watermarking as the extracting process doesn't need the original program. Only changing the last parameter of the call function and calculating, the watermarking is extracted. Research shows that this algorithm has good ability of resistance to the attack, and the performance of the program is influenced less after embedding watermarking.Finally a detecting scheme of software watermarking on zero-knowledge proof is designed. The most important feature is to open the water recognizer, which allows the end user as a verifier to identify the reliability and the true copyright author of the software work. The software watermarking is recognized dynamically by the interactive communication which is challenge and response between the proofer and the verifier. The whole detecting process will not reveal any watermarking message and implement a zero-knowledge proof protocol.The two kinds of software watermarking algorithms and a watermarking detecting scheme are all improvement for the current technology of software protection, which make a solution to the partial flow and leak in the traditional algorithms and have good practical value.