Combined Fault and Side-Channel Attacks on the AES Key Schedule

Author(s):  
Francois Dassance ◽  
Alexandre Venelli
Author(s):  
Johann Heyszl ◽  
Katja Miller ◽  
Florian Unterstein ◽  
Marc Schink ◽  
Alexander Wagner ◽  
...  

Recent publications describe profiled single trace side-channel attacks (SCAs) against the DES key-schedule of a “commercially available security controller”. They report a significant reduction of the average remaining entropy of cryptographic keys after the attack, with surprisingly large, key-dependent variations of attack results, and individual cases with remaining key entropies as low as a few bits. Unfortunately, they leave important questions unanswered: Are the reported wide distributions of results plausible - can this be explained? Are the results device-specific or more generally applicable to other devices? What is the actual impact on the security of 3-key triple DES? We systematically answer those and several other questions by analyzing two commercial security controllers and a general purpose microcontroller. We observe a significant overall reduction and, importantly, also observe a large key-dependent variation in single DES key security levels, i.e. 49.4 bit mean and 0.9 % of keys < 40 bit (first investigated security controller; other results similar). We also observe a small fraction of keys with exceptionally low security levels that can be called weak keys. It is unclear, whether a device’s side-channel security should be assessed based on such rare weak key outliers. We generalize results to other leakage models by attacking the hardware DES accelerator of a general purpose microcontroller exhibiting a different leakage model. A highly simplified leakage simulation also confirms the wide distribution and shows that security levels are predictable to some extent. Through extensive investigations we find that the actual weakness of keys mainly stems from the specific switching noise they cause. Based on our investigations we expect that widely distributed results and weak outliers should be expected for all profiled attacks against (insufficiently protected) key-schedules, regardless of the algorithm and specific implementation. Finally, we describe a sound approach to estimate actual 3-key triple-DES security levels from empirical single DES results and find that the impact on the security of 3-key triple-DES is limited, i.e. 96.1 bit mean and 0.24 % of key-triples < 80 bit for the same security controller.


Author(s):  
Andreas Wiemers ◽  
Johannes Mittmann

AbstractRecent publications consider side-channel attacks against the key schedule of the Data Encryption Standard (DES). These publications identify a leakage model depending on the XOR of register values in the DES key schedule. Building on this leakage model, we first revisit a discrete model which assumes that the Hamming distances between subsequent round keys leak without error. We analyze this model formally and provide theoretical explanations for observations made in previous works. Next we examine a continuous model which considers more points of interest and also takes noise into account. The model gives rise to an evaluation function for key candidates and an associated notion of key ranking. We develop an algorithm for enumerating key candidates up to a desired rank which is based on the Fincke–Pohst lattice point enumeration algorithm. We derive information-theoretic bounds and estimates for the remaining entropy and compare them with our experimental results. We apply our attack to side-channel measurements of a security controller. Using our enumeration algorithm we are able to significantly improve the results reported previously for the same measurement data.


2009 ◽  
Vol 19 (11) ◽  
pp. 2990-2998 ◽  
Author(s):  
Tao ZHANG ◽  
Ming-Yu FAN

2021 ◽  
Vol 13 (6) ◽  
pp. 146
Author(s):  
Somdip Dey ◽  
Amit Kumar Singh ◽  
Klaus McDonald-Maier

Side-channel attacks remain a challenge to information flow control and security in mobile edge devices till this date. One such important security flaw could be exploited through temperature side-channel attacks, where heat dissipation and propagation from the processing cores are observed over time in order to deduce security flaws. In this paper, we study how computer vision-based convolutional neural networks (CNNs) could be used to exploit temperature (thermal) side-channel attack on different Linux governors in mobile edge device utilizing multi-processor system-on-chip (MPSoC). We also designed a power- and memory-efficient CNN model that is capable of performing thermal side-channel attack on the MPSoC and can be used by industry practitioners and academics as a benchmark to design methodologies to secure against such an attack in MPSoC.


2021 ◽  
Vol 21 (3) ◽  
pp. 1-20
Author(s):  
Mohamad Ali Mehrabi ◽  
Naila Mukhtar ◽  
Alireza Jolfaei

Many Internet of Things applications in smart cities use elliptic-curve cryptosystems due to their efficiency compared to other well-known public-key cryptosystems such as RSA. One of the important components of an elliptic-curve-based cryptosystem is the elliptic-curve point multiplication which has been shown to be vulnerable to various types of side-channel attacks. Recently, substantial progress has been made in applying deep learning to side-channel attacks. Conceptually, the idea is to monitor a core while it is running encryption for information leakage of a certain kind, for example, power consumption. The knowledge of the underlying encryption algorithm can be used to train a model to recognise the key used for encryption. The model is then applied to traces gathered from the crypto core in order to recover the encryption key. In this article, we propose an RNS GLV elliptic curve cryptography core which is immune to machine learning and deep learning based side-channel attacks. The experimental analysis confirms the proposed crypto core does not leak any information about the private key and therefore it is suitable for hardware implementations.


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