Detecting Hidden Leakages

Abstract

Abstract. Reducing the entropy of the mask is a technique which has been proposed to mitigate the high performance overhead of masked software implementations of symmetric block ciphers. Rotating S-box Masking (RSM) is an example of such schemes applied to AES with the purpose of maintaining the security at least against univariate first-order side-channel attacks. This article examines the vulnerability of a realization of such technique using the side-channel measurements publicly available through DPA contest V4. Our analyses which focus on exploiting the first-order leakage of the implementation discover a couple of potential attacks which can recover the secret key. Indeed the leakage we exploit is due to a design mistake as well as the characteristics of the implementation platform, none of which has been considered during the design of the countermeasure (implemented in naive C code).

k-Nearest Neighbors Algorithm in Profiling Power Analysis Attacks

“…The masked block-cipher AES-256 in encryption mode without any mode of operation is implemented on target cryptographic device Atmel ATMega-163-based smart card. The implemented masking scheme is a variant of the Rotating Sbox Masking [23], [64]. According to the authors, this masking scheme keeps performance and complexity close to the unprotected scheme and is resistant to several side-channel attacks.…”

“…offset value, which is drawn randomly at the beginning of computation, is a secret value. Mask values are rotating according to the offset value [23], [64]. Each stored trace has 435 002 samples associated to the same secret key and corresponds to the first and to the beginning of the second round of AES algorithm.…”

Side-channel leakage and trace compression using normalized inter-class variance

“…Similarly MixColumns can also be identified by just looking the bytes manipulated together. Moreover, detecting precise leakage points of each operation can help an attacker run collision attacks (see e.g., [27,26]). …”

Boosting Higher-Order Correlation Attacks by Dimensionality Reduction

“…In RSM only sixteen Substitution boxes (S-boxes) are used and all the sixteen outputs of SubBytes are masked by a different mask. We take great in this paper to exploit second-order leakage (in particular, we avoid the first-order leakage identified by Moradi et al [15]). Moreover, the same mask is used for the AddRoundKey operation where it is XORed to one plaintext byte P and in the SubBytes operation where it is XORed with the S-box output depending on another plaintext byte P .…”