Optimizing RTL Code Obfuscation: New Methods Based on XML Syntax Tree

Abstract

As the most widely used description code in digital circuits and system on chip (SoC), the security of register transfer level (RTL) code is extremely critical. Code obfuscation is a typical method to ensure the security of RTL code, but popular obfuscation methods are not fully applicable to RTL code. In addition, some RTL code obfuscation tools also have issues with incomplete functionality or obfuscation errors. In view of the above issues, this paper studies the RTL code security problem represented by obfuscation. Based on the extensible markup language (XML) syntax tree generated by parsing RTL code, a complete RTL code refactoring model is constructed, and four targeted RTL code obfuscation methods are proposed, namely: Layout obfuscation; Parameter obfuscation; Critical path obfuscation; Code increment obfuscation. Utilizing the developed obfuscation tool, an assessment of the performance and effectiveness of the obfuscation methods is conducted, alongside testing the equivalence between the obfuscated code and the source code. The experimental results show that the proposed obfuscation methods have higher practicability and reliability, and have the characteristics of high obfuscation coverage that can be stable at over 98% and preservation of compiler indicative Comments.