Two Improved Multiple-Differential Collision Attacks

In CHES 2008, Bogdanov proposed multiple-differential collision attacks which could be applied to the power analysis attacks on practical cryptographic systems. However, due to the effect of countermeasures on FPGA, there are some difficulties during the collision detection, such as local high noise and the lack of sampling points. In this paper, keypoints voting test is proposed for solving these problems, which can increase the success ratio from 35% to 95% on the example of one implementation. Furthermore, we improve the ternary voting test of Bogdanov, which can improve the experiment efficiency markedly. Our experiments show that the number of power traces required in our attack is only a quarter of the requirement of traditional attack. Finally, some alternative countermeasures against our attacks are discussed

Near Collision Side Channel Attacks

Side channel collision attacks are a powerful method to exploit side channel leakage. Otherwise than a few exceptions, collision attacks usually combine leakage from distinct points in time, making them inherently bivariate. This work introduces the notion of near collisions to exploit the fact that values depending on the same sub-key can have similar while not identical leakage. We show how such knowledge can be exploited to mount a key recovery attack. The presented approach has several desirable features when compared to other state-of-the-art collision attacks: Near collision attacks are truly univariate. They have low requirements on the leakage functions, since they work well for leakages that are linear in the bits of the targeted intermediate state. They are applicable in the presence of masking countermeasures if there exist distinguishable leakages, as in the case of leakage squeezing. Results are backed up by a broad range of simulations for unprotected and masked implementations, as well as an analysis of the measurement set provided by DPA Contest v4

Unified and Optimized Linear Collision Attacks and Their Application in a Non-profiled Setting

Side-channel collision attacks are one of the most investigated techniques allowing the combination of mathematical and physical cryptanalysis. In this paper, we discuss their relevance in the security evaluation of leaking devices with two main contributions. On the one hand, we suggest that the exploitation of linear collisions in block ciphers can be naturally re-written as a Low Density Parity Check Code decoding problem. By combining this re-writing with a Bayesian extension of the collision detection techniques, we succeed in improving the efficiency and error tolerance of previously introduced attacks. On the other hand, we provide various experiments in order to discuss the practicality of such attacks compared to standard DPA. Our results exhibit that collision attacks are less efficient in classical implementation contexts, e.g. 8-bit microcontrollers leaking according to a linear power consumption model. We also observe that the detection of collisions in software devices may be difficult in the case of optimized implementations, because of less regular assembly codes. Interestingly, the soft decoding approach is particularly useful in these more challenging scenarios. Finally, we show that there exist (theoretical) contexts in which collision attacks succeed in exploiting leakages whereas all other non-profiled side-channel attacks fail

Unified and optimized linear collision attacks and their application in a non-profiled setting

Side-channel collision attacks are one of the most investigated techniques allowing the combination of mathematical and physical cryptanalysis. In this paper, we discuss their relevance in the security evaluation of leaking devices with two main contributions. On the one hand, we suggest that the exploitation of linear collisions in block ciphers can be naturally re-written as a Low Density Parity Check Code decoding problem. By combining this re-writing with a Bayesian extension of the collision detection techniques, we succeed in improving the efficiency and error tolerance of previously introduced attacks. On the other hand, we provide various experiments in order to discuss the practicality of such attacks compared to standard DPA. Our results exhibit that collision attacks are less efficient in classical implementation contexts, e.g. 8-bit microcontrollers leaking according to a linear power consumption model.We also observe that the detection of collisions in software devices may be difficult in the case of optimized implementations, because of less regular assembly codes. Interestingly, the soft decoding approach is particularly useful in these more challenging scenarios. Finally, we show that there exist (theoretical) contexts in which collision attacks succeed in exploiting leakages whereas all other non-profiled side-channel attacks fail