Secure Scan Design with a Novel Methodology of Scan Camouflaging

Scan based attacks are the major security concerns of a design. These attacks are majorly employed to understand the camouflaged logic during reverse engineering. The state- of-the-art techniques like scan chain scrambling hinder accessibility of scan chains, but are prone to layout level reverse engineering attacks. In the proposed methodology, the scan design is secured by adding an extra scan input port (DSI) to the flipflop using dummy contacts, which ensure that DSI cannot be distinguished from SI port even with layout based reverse engineering techniques. Dummy scan chain connections are introduced in the design by connecting DSI port to the nearby flipflop Q output port. Our proposed method can withstand Reset-and-scan attack, Incremental SAT-based attack and the recent ScanSAT attack. The performance of this concept is measured in terms of frequency and total power consumption on IWLS-2005 benchmark circuits having up to 1380 flipflops with 40nm technology library. The delay is effected by a maximum of 2.2% with 50% obfuscation without any impact on power, pattern generation time and scan test time.