Exploiting number theory for dynamic software watermarking

Software watermarking is a protection technique which aims at combating software piracy, thus defending intellectual property, by embedding stegosignatures or watermarks into a program. In the presence of an illegal copy of the program, the owner can reliably claim her rights by extracting the watermark from the program itself. In this paper, we introduce a new software watermarking technique which can be used even with compiled programs. The proposed technique is dynamic: the watermark can be recovered during the execution of the program and it is related to a specific path of execution that is triggered by a given input. We illustrate the technique by means of a watermarking protocol for C/C++/C# source code which tackles many different challenges in the task of encoding the watermark, embedding it into a source code and extracting it from a compiled program. We show the validity of our approach by proving its robustness against common attacks.