Security Analysis of State-of-the-art Scan Obfuscation Technique

Scan-based Design for Testability (DfT) is the defacto standard for detecting manufacturing-related faults in chip manufacturing industries. The observability and accessibility provided by DfT can be misused to launch an attack to reveal the secret key, which is embedded inside a crypto chip. Several countermeasures have been proposed to protect the chip against scan-based attacks. Dynamic obfuscation of scan data prevents scan-based attacks by corrupting scan data in the case of unauthorized access. In this paper, we perform the security analysis of the above state-of-the-art obfuscation technique to showcase its vulnerabilities. Exploiting its vulnerabilities, we propose a scan-based signature attack on state-of-the-art obfuscation technique by applying a maximum of 4096 plaintexts and using only 220 signatures with a 100% success rate.