An Analysis of Stream and Block Ciphers for Scan Encryption

Scan-based test methodology is one of the most popular test techniques in VLSI circuits. This methodology increases the testability which in turn improves the fault coverage. For this purpose, the technique uses a chain of scan cells. This becomes a source of attack for an attacker who can observe / control the internal states and use the information for malicious purposes. Hence, security becomes the main concern in the Integrated Circuit (IC) domain since scan chains are the main reason for leakage of confidential information during testing phase. These leakages will help attackers in reverse engineering. Measures against such attacks have to be taken by encrypting the data which flows through the scan chains. Lightweight ciphers can be used for scan chain encryption. In this work, encryption of scan data is done for ISCAS-89 benchmarks and the performance and security properties are evaluated. Lightweight stream and block ciphers are used to perform scan encryption. A comparative analysis between the two techniques is performed in par with the functions related to design cost and security properties.