Cryptology ePrint Archive: Report 2014/263

A Generic Scan Attack on Hardware based eStream Winners

Sandip Karmakar and Dipanwita Roy Chowdhury

Abstract: Scan chains, a design for testability (DFT) feature, are included in most modern-day ICs. But, it opens a side channel for attacking cryptographic chips. We propose a methodology by which we can recover internal states of any stream cipher using scan chains without knowledge of its design. We consider conven- tional scan-chain design which is normally not scram- bled or protected in any other way. In this scenario the challenge of the adversary is to obtain the corre- spondence of output of the scan chain and the internal state registers of the stream cipher. We present a math- ematical model of the attack and the correspondence between the scan chain-outputs and the internal state bits have been proved under this model. We propose an algorithm that through o -line and on-line simulation forms bijection between the above mentioned sets and thus nds the required correspondence. We also give an estimate of the number of o -line simulations necessary for nding the correspondence. The proposed strategy is successfully applied to eS- tream hardware based nalists MICKEY-128 2.0, Triv- ium and Grain-128. To the best of our knowledge, this is the rst scan based attack against full round Grain-128 and only the fourth reported cryptanalysis. This attack on Trivium is better than that of the published scan- attack on Trivium. This scan-based attack is also the rst reported scan based cryptanalysis against MICKEY- 128 2.0.

Category / Keywords: secret-key cryptography / Scan Attack, eStream Winners, Side Channel Attack, Grain-128, Trivium, MICKEY-128 2.0

Date: received 14 Apr 2014

Contact author: sandip1kk at gmail com

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Version: 20140420:153717 (All versions of this report)

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