Sandip Karmakar

Scan Based Side Channel Attacks on Stream Ciphers and Their Counter-Measures

Scan chain based attacks are a kind of side channel attack, which targets one of the most important feature of todays hardware - the test circuitry. Design for Testability (DFT) is a design technique that adds certain testability features to a hardware design. On the other hand, this very feature opens up a side channel for cryptanalysis, rendering crypto-devices vulnerable to scan-based attack. Our work studies scan attack as a general threat to stream ciphers and arrives at a general relation between the design of stream ciphers and their vulnerability to scan attack. Finally, we propose a scheme which we show to thwart the attacks and is more secure than other contemporary strategies.

Fault analysis of grain-128 by targeting NFSR

Fault attack is one of the most efficient form of side channel attack against implementations of cryptographic algorithms. This kind of attacks have been shown to be extremely successful against stream ciphers. The eStream cipher Grain-128 has already been shown to be weak against fault attack, when faults are injected in the LFSR. In this paper, we show that Grain-128 can also be attacked by inducing faults in the NFSR. The attack requires about 56 fault injections for NFSR and a computational complexity of about 221.

Differential Fault Analysis of MICKEY-128 2.0

This paper presents a differential fault analysis of the MICKEY-128 2.0 stream cipher, one of the finalist of eStream project. The current attack works on MICKEY-128 2.0 with 320 state register-bits and requires 480 number of random single bit faults to break it. Till date, only two fault attacks against MICKEY family are available in literature, one attack on MICKEY-128 and another on MICKEY 2.0. The attack on MICKEY-128 with same 320 register bits required 640 number of faults whereas the other attack on MICKEY 2.0 with 200 state register bits required

d-monomial tests of nonlinear cellular automata for cryptographic design

2^{16.7} number of faults. To the best of our knowledge the current attack gives the best performance with respect to the number of faults to be induced against the highest version of MICKEY, MICKEY-128 2.0.

Leakage Squeezing Using Cellular Automata

Pseudorandom generation is a key to any cryptographic application. Linear Cellular Automata are known as good pseudorandom generators. However, for cryptographic applications nonlinearity is essential for its security. But, nonlinear Cellular Automaton shows high correlation between the input to the automaton and its generated sequence. Hence, for cryptography Cellular Automata rules need to be nonlinear as well as satisfy additional properties. With this motivation, in this paper, we analyze nonlinear Cellular Automata with a newly developed statistical measure called d-monomial test. Finally, we propose a process of d-monomial characteristics addition to get cryptographically suitable Cellular Automata.

Countermeasures of Side Channel Attacks on Symmetric Key Ciphers Using Cellular Automata

Leakage squeezing is a novel approach towards resisting side channel attacks against cryptographic implementations. It is seen that certain codes are ideal for leakage squeezing applications. However, in this paper we argue that few other cryptographic properties are essential for better squeezing. In this respect we analyze few Cellular Automata (CA) configurations towards suitability in leakage squeezing. It is argued that nonlinear cellular automata with respective cryptographic and code properties are ideal for applications in this scenario.

CAvium - Strengthening Trivium Stream Cipher Using Cellular Automata

Side Channel Attacks (SCA) are one of the most effective means in breaking symmetric key ciphers. Generally, SCA exploits the side-channel leakages output by the implementations of ciphers or introduces defects in the system to analyze them. A number of countermeasures have been proposed to strengthen/remedy implementations of ciphers against SCA. However, none of the countermeasures, to our knowledge, are good enough towards its goal ([16], [19], [3]). In this paper, we emphasis on the necessity of randomness in designing countermeasures against SCA and propose Cellular Automata (CA) based system to thwart SCA. Our countermeasure is also analyzed against popular SCA, such as, differential power attack (DPA), scan-chain based attacks (SC-SCA) and fault attacks (FA).