Research On Software Watermarking Algorithm And Implementation

With the rapid development of information technology, the software industry obtains a newopportunity, however, malicious software piracy and illegal use is more and more grim, the softwareintellectual property protection becomes increasingly prominent.A software watermarking algorithm based on stack allocation has been proposed in this paperaccording to the theory of spread spectrum communication. By studying the characteristic of dynamicgraph encoding, we found two critical shortages: one hand is that graph encoding efficiency is lower;on the other hand is that watermark topographies have no dependency with the host.Against thecoding efficiency problem, we propose an improved PPCT structure that is ExtendPPCT.Against theproblem that watermark topographies have no dependency with the host, we propose atamper-proofing scheme which based on ExtendPPCT. The main work is as follows:(1). The paper proposes a static software watermarking algorithm based on stack allocation, andgiven three principles to select feature vectors.The scheme embeds watermark information bymodifying the size of the stack, and then applies the stack access confusion technology to makesoftware watermark information and the program code produce a close dependency, finally, appliesthe stack filtering technology to filter illegal modified stack when needs extraction. Analysis showsthat the algorithm has a higher robustness and invisibility, especially, it is suitable for protecting thelarger software products.(2). The paper proposes an improved PPCT structure that is ExtendPPCT. Against low efficiency ofPPCT encoding, we proposes an idea that taken fixed logical sequences as linked list whichenlightened by IPPCT encoding, and puts forward the ExtendPPCT structure to make full use ofPPCT’s nodes, and then brings forword two kinds of hybrid encoding schemes based onExtendPPCT.Stduy shows improved PPCT compares with traditional dynamic graph not only haveobvious advantages in data rate and robustness, but also each watermark numbers have a variety ofdifferent encoding forms, which means it can effectively resist conspiracy attacks.(3). The paper proposes a tamper-proofing software watermark scheme based on ExtendPPCT.Against the problem that no matter takes what kinds of encoding the generated watermarktopographies have no dependency with the host and independent from each other, we proposes an ideathat encoding constant variable by using ExtendPPCT’s leaves’s right pointers, which makeswatermark and tamper-proofing constant encode into the same structure, and leading a closerdependency between watermark topographies with the host, and then obtain the ability of resisting conspiracy attacks.(4). We implements ExtendPPCT with radix-k hybrid encoding and ExtendPPCT with permutationgraph hybrid encoding as well as a tamper-proofing software watermark scheme based onExtendPPCT on SandMark experiment platform. And then carry out a detailed performanceevaluation for the proposed scheme on the SandMark platform.