Fault Attacks In Symmetric Key Cryptosystems

Fault attacks are among the well-studied topics in the area of cryptography. These attacks constitute a powerful tool to recover the secret key used in the encryption process. Fault attacks work by forcing a device to work under non-ideal environmental conditions (such as high temperature) or external disturbances (such as glitch in the power supply) while performing a cryptographic operation. The recent trend shows that the amount of research in this direction; which ranges from attacking a particular primitive, proposing a fault countermeasure, to attacking countermeasures; has grown up substantially and going to stay as an active research interest for a foreseeable future. Hence, it becomes apparent to have a comprehensive yet compact study of the (major) works. This work, which covers a wide spectrum in the present day research on fault attacks that fall under the purview of the symmetric key cryptography, aims at fulfilling the absence of an up-to-date survey. We present mostly all aspects of the topic in a way which is not only understandable for a non-expert reader, but also helpful for an expert as a reference

SoK: Parameterization of Fault Adversary Models - Connecting Theory and Practice

Since the first fault attack by Boneh et al. in 1997, various physical fault injection mechanisms have been explored to induce errors in electronic systems. Subsequent fault analysis methods of these errors have been studied, and successfully used to attack many cryptographic implementations. This poses a significant challenge to the secure implementation of cryptographic algorithms. To address this, numerous countermeasures have been proposed. Nevertheless, these countermeasures are primarily designed to protect against the particular assumptions made by the fault analysis methods. These assumptions, however, encompass only a limited range of the capabilities inherent to physical fault injection mechanisms. In this paper, we narrow our focus to fault attacks and countermeasures specific to ASICs, and introduce a novel parameterized fault adversary model capturing an adversary\u27s control over an ASIC. We systematically map (a) the physical fault injection mechanisms, (b) adversary models assumed in fault analysis, and (c) adversary models used to design countermeasures into our introduced model. This model forms the basis for our comprehensive exploration that covers a broad spectrum of fault attacks and countermeasures within symmetric key cryptography as a comprehensive survey. Furthermore, our investigation highlights a notable misalignment among the adversary models assumed in countermeasures, fault attacks, and the intrinsic capabilities of the physical fault injection mechanisms. Through this study, we emphasize the need to reevaluate existing fault adversary models, and advocate for the development of a unified model

Reduction in the Number of Fault Injections for Blind Fault Attack on SPN Block Ciphers

In 2014, a new fault analysis called blind fault attack (BFA) was proposed, in which attackers can only obtain the number of different faulty outputs without knowing the public data. The original BFA requires 480,000 fault injections to recover a 128-bit AES key. This work attempts to reduce the number of fault injections under the same attack assumptions. We analyze BFA from an information theoretical perspective and introduce a new probability-based distinguisher. Three approaches are proposed for different attack scenarios. The best one realized a 66.8% reduction of the number of fault injections on AES

Degenerate Curve Attacks

Invalid curve attacks are a well-known class of attacks against implementations of elliptic curve cryptosystems, in which an adversary tricks the cryptographic device into carrying out scalar multiplication not on the expected secure curve, but on some other, weaker elliptic curve of his choosing. In their original form, however, these attacks only affect elliptic curve implementations using addition and doubling formulas that are independent of at least one of the curve parameters. This property is typically satisfied for elliptic curves in Weierstrass form but not for newer models that have gained increasing popularity in recent years, like Edwards and twisted Edwards curves. It has therefore been suggested (e.g. in the original paper on invalid curve attacks) that such alternate models could protect against those attacks. In this paper, we dispel that belief and present the first attack of this nature against (twisted) Edwards curves, Jacobi quartics, Jacobi intersections and more. Our attack differs from invalid curve attacks proper in that the cryptographic device is tricked into carrying out a computation not on another elliptic curve, but on a group isomorphic to the multiplicative group of the underlying base field. This often makes it easy to recover the secret scalar with a single invalid computation. We also show how our result can be used constructively, especially on curves over random base fields, as a fault attack countermeasure similar to Shamir\u27s trick

Differential Fault Attack on Ascon Cipher

This work investigates the security of the Ascon authenticated encryption scheme in the context of fault attacks, with a specific focus on Differential Fault Analysis (DFA). Motivated by the growing significance of lightweight cryptographic solutions, particularly Ascon, we explore potential vulnerabilities in its design using DFA. By employing a novel approach that combines faulty forgery in the decryption query under two distinct fault models, leveraging bit-flip faults in the first phase and bit-set faults in the second, we successfully recover the complete Ascon key. This study sheds light on the impact of key whitening in the final permutation call and discusses potential threats when this safeguard is absent. Additionally, we consider the implications of injecting multiple bit-flip faults at the S-box input, suggesting alternative strategies for compromising the state space. Our findings contribute valuable insights into the gray-box security landscape of Ascon, emphasizing the need for robust defenses to ensure the integrity and resilience of lightweight cryptographic primitives against diverse fault attacks

Linked Fault Analysis

Numerous fault models have been developed, each with distinct characteristics and effects. These models should be evaluated in light of their costs, repeatability, and practicability. Moreover, there must be effective ways to use the injected fault to retrieve the secret key, especially if there are some countermeasures in the implementation. In this paper, we introduce a new fault analysis technique called ``linked fault analysis\u27\u27 (LFA), which can be viewed as a more powerful version of well-known fault attacks against implementations of symmetric primitives in various circumstances, especially software implementations. For known fault analyses, the bias over the faulty value or the relationship between the correct value and the faulty one, both produced by the fault injection serve as the foundations for the fault model. In the LFA, however, a single fault involves two intermediate values. The faulty target variable, $u\u27$, is linked to a second variable, $v$, such that a particular relation holds: $u\u27=l(v)$. We show that LFA lets the attacker perform fault attacks without the input control, with much fewer data than previously introduced fault attacks in the same class. Also, we show two approaches, called LDFA and LIFA, that show how LFA can be utilized in the presence or absence of typical redundant-based countermeasures. Finally, we demonstrate that LFA is still effective, but under specific circumstances, even when masking protections are in place. We performed our attacks against the public implementation of AES in ATMEGA328p to show how LFA works in the real world. The practical results and simulations validate our theoretical models as well

To Infect Or Not To Infect: A Critical Analysis Of Infective Countermeasures In Fault Attacks

As fault based cryptanalysis is becoming more and more of a practical threat, it is imperative to make efforts to devise suitable countermeasures. In this regard, the so-called ``infective countermeasures\u27\u27 have garnered particular attention from the community due to its ability in inhibiting differential fault attacks without explicitly detecting the fault. We observe that despite being adopted over a decade ago, a systematic study of infective countermeasures is missing from the literature. Moreover, there seems to be a lack of proper security analysis of the schemes proposed, as quite a few of them have been broken promptly. Our first contribution comes in the form of a generalization of infective schemes which aids us with a better insight into the vulnerabilities, scopes for cost reduction and possible improvements. This way, we are able to propose lightweight alternatives of two existing schemes. Further we analyze shortcomings of LatinCrypt\u2712 and CHES\u2714 schemes and propose a simple patch for the former

Minefield: A Software-only Protection for SGX Enclaves against DVFS Attacks

Modern CPUs adapt clock frequencies and voltage levels to workloads to reduce energy consumption and heat dissipation. This mechanism, dynamic voltage and frequency scaling (DVFS), is controlled from privileged software but affects all execution modes, including SGX. Prior work showed that manipulating voltage or frequency can fault instructions and thereby subvert SGX enclaves. Consequently, Intel disabled the overclocking mailbox (OCM) required for software undervolting, also preventing benign use for energy saving. In this paper, we propose Minefield, the first software-level defense against DVFS attacks. The idea of Minefield is not to prevent DVFS faults but to deflect faults to trap instructions and handle them before they lead to harmful behavior. As groundwork for Minefield, we systematically analyze DVFS attacks and observe a timing gap of at least 57.8 us between every OCM transition, leading to random faults over at least 57000 cycles. Minefield places highly fault-susceptible trap instructions in the victim code during compilation. Like redundancy countermeasures, Minefield is scalable and enables enclave developers to choose a security parameter between 0% and almost 100%, yielding a fine-grained security-performance trade-off. Our evaluation shows a density of 0.75, i.e., one trap after every 1-2 instruction, mitigates all known DVFS attacks in 99% on Intel SGX, incurring an overhead of 148.4% on protected enclaves. However, Minefield has no performance effect on the remaining system. Thus, Minefield is a better solution than hardware- or microcode-based patches disabling the OCM interface

The Random Fault Model

In this work, we introduce the random fault model - a more advanced fault model inspired by the random probing model, where the adversary can fault all values in the algorithm but the probability for each fault to occur is limited. The new adversary model is used to evaluate the security of side-channel and fault countermeasures such as Boolean masking, error detection techniques, error correction techniques, multiplicative tags, and shuffling methods. The results of the security analysis reveal new insights both in the novel random fault model as well as in the established random probing model including: shuffling masked implementations does not significantly improve the random probing security over regular masking; error correction providing little security when faults target more bits (versus the significant improvement when using error detection); and the order in which masking and duplication are applied providing a trade-off between random probing and fault security. Moreover, the results also explain the experimental results from CHES 2022 and find weaknesses in the shuffling method from SAMOS 2021

Lightweight Fault Attack Resistance in Software Using Intra-Instruction Redundancy

Fault attack countermeasures can be implemented by storing or computing sensitive data in redundant form, such that the faulty data can be detected and restored. We present a class of lightweight, portable software countermeasures for block ciphers. Our technique is based on redundant bit-slicing, and it is able to detect faults in the execution of a single instruction. In comparison to earlier techniques, we are able to intercept data faults as well as instruction sequence faults using a uniform technique. Our countermeasure thwarts precise bit-fault injections through pseudo-random shifts in the allocation of data bit-slices. We demonstrate our solution on a full AES design and confirm the claimed security protection through a detailed fault simulation for a 32-bit embedded processor. We also quantify the overhead of the proposed fault countermeasure, and find a minimal increase in footprint (14%), and a moderate performance overhead between 125% to 317%, depending on the desired level of fault-attack resistance