Code obfuscation using very long identifiers for FFT motion estimation models in embedded processors

Abstract

Motion estimation is extensively used in multimedia tasks, video coding standards and home consumer devices, appearing in many FFT-based motion algorithms. On other hand, the intellectual properties of embedded microprocessor systems are typically delivered on HDL and C source code levels. Obfuscating the code is most often the only way to protect and avoid reverse engineering. This paper presents an evaluation of operations widely used in motion estimation for an embedded microprocessor for protection purposes. A set of open source obfuscation tools has been developed that allows the use of very long and hard-to-read identifiers. The implementation of comment methods also allows for the addition of copyright and limited warranty information. The obfuscated code with identifiers of up to 2,048 characters in length is tested for Altera's and Xilinx's field programmable gate arrays for a typical HDL example. Compiler penalties as well as FFT runtime results are reported.