Dynamic Interposer Obfuscation through Distributed Scramblers in Heterogeneously Integrated 2.5D ICs*

Recent breakthroughs in heterogeneous integration (HI) using 2.5D and 3D ICs have been key to advances in the semiconductor industry. However, heterogeneous integration has also led to several sources of distrust due to the use of thirdparty IP, testing, and fabrication facilities in the design and manufacturing process. Recent work on 2.5D IC security has focused on attacks that can be mounted through rogue chiplets integrated in the design. Thus, existing solutions implement interchiplet communication protocols that prevent unauthorized data modification and interruption in a 2.5D system. However, none of the existing solutions offer inherent security against IP theft. We develop a comprehensive threat model for 2.5D systems indicating that such systems remain vulnerable to IP theft. We present a method that prevents IP theft by obfuscating the connectivity of chiplets on the interposer using reconfigurable interconnection networks. We further achieve dynamic obfuscation of chiplet interconnects while demonstrating resilience against removal, data-snooping, test-based data leakage attacks. We present an approach to implement reconfigurable chiplet interconnection networks through both centralized and distributed scrambler designs, evaluating the security and implementation benefits of both the architectures. We present a comprehensive methodology to design, implement, and integrate interconnect scramblers in a large 2.5D HI system. We also evaluate the power, performance, and area overhead for both distributed and centralized scramblers.