A Survey of Software Watermarking by Register Allocation (for Java Bytecode)

Software watermarking involves embedding a unique identifier within a piece of software, to discourage software theft. The global revenue loss due to software piracy was estimated to be more than $50 billion in 2008. We survey the proposed register allocation based algorithms for software watermarking. This family of static watermarks are constraint-based and embed the watermark in a solution to a graph colouring problem; the graph colouring is then used to allocate registers. Register allocation is the process of allocating program variables to a finite number of CPU registers and a compiler commonly uses graph colouring to obtain the best allocation. We describe the existing techniques and highlight the short-comings of these algorithms, namely that they are highly susceptible to semantics preserving transformations. Keywords-software watermarking; register allocation; graph colouring; program transformation;java; bytecode;