Experimentations on scan chain encryption with PRESENT

Abstract

Crypto-processors are vulnerable to scan attacks. Using the scan chain, an attacker is indeed able to observe intermediate encryption states and steal secret data closely-related to the key. However, scan design is the most powerful mean for test and diagnostic purpose. Several countermeasure approaches have thus been proposed for securing scan designs while preserving test efficiency, diagnosis and debugging abilities. One solution is to encrypt test patterns thanks to extra block ciphers preventing control and observation of plain texts in the scan chain. The goal of this paper is to experiment this scan chain encryption approach on different designs in order to evaluate test efficiency and costs in terms of area and test time.