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

When Theory Meets Practice: A Framework for Robust Profiled Side-channel Analysis

Profiled side-channel attacks are the most powerful attacks and they consist of two steps. The adversary first builds a leakage model, using a device similar to the target one, then it exploits this leakage model to extract the secret information from the victim's device. These attacks can be seen as a classification problem, where the adversary needs to decide to what class (corresponding to the secret key) the traces collected from the victim's devices belong to. For a number of years, the research community studied profiled attacks and proposed numerous improvements. Despite a large number of empirical works, a framework with strong theoretical foundations to address profiled side-channel attacks is still missing. In this paper, we propose a framework capable of modeling and evaluating all profiled analysis attacks. This framework is based on the expectation estimation problem that has strong theoretical foundations. Next, we quantify the effects of perturbations injected at different points in our framework through robustness analysis where the perturbations represent sources of uncertainty associated with measurements, non-optimal classifiers, and methods. Finally, we experimentally validate our framework using publicly available traces, different classifiers, and performance metrics

SoK : Remote Power Analysis

In recent years, numerous attacks have appeared that aim to steal secret information from their victim using the power side-channel vector, yet without direct physical access. These attacks are called Remote Power Attacks or Remote Power Analysis, utilizing resources that are natively present inside the victim environment. However, there is no unified definition about the limitations that a power attack requires to be defined as remote. This paper aims to propose a unified definition and concrete threat models to clearly differentiate remote power attacks from non-remote ones. Additionally, we collect the main remote power attacks performed so far from the literature, and the principal proposed countermeasures to avoid them. The search of such countermeasures denoted a clear gap in preventing remote power attacks at the technical level. Thus, the academic community must face an important challenge to avoid this emerging threat, given the clear room for improvement that should be addressed in terms of defense and security of devices that work with private information.acceptedVersionPeer reviewe

EM Side Channel Analysis on Complex SoC architectures

The EM side channel analysis is a very effective technique to attack cryptographic systems due to its non invasive nature and capability to launch an attack even with limited resources. The EM leakage from devices can give information about computations on the processor, which can in turn reveal the internal state of the algorithm. For security sensitive algorithms, these EM radiations can be exploited by the adversary to extract secret key dependent operations hence EM side channel must be studied for evaluating the security of these algorithms. Modern embedded devices composed of System-on-Chip architectures are considered hard targets for EM side channel analysis mainly due to their complex architecture. This thesis explores the viability of EM side channel attacks on such targets. There is a comprehensive literature overview of EM side channel analysis followed by a practical side channel attack on a SoC device using well know cryptographic library OpenSSL. The attack successfully extracts the secret key dependent operation which can be used to retrieve the private key in security protocols such as TLS and SSH. The thesis concludes, with practical single trace attacks, that cryptographic implementations can still be broken using EM side channel analysis, and a complex nature of the device have no significant effect when combined with signal processing methods for extracting side channel information, hence the cryptographic software implementations must address these issues

Side-Channel Analysis and Cryptography Engineering : Getting OpenSSL Closer to Constant-Time

As side-channel attacks reached general purpose PCs and started to be more practical for attackers to exploit, OpenSSL adopted in 2005 a flagging mechanism to protect against SCA. The opt-in mechanism allows to flag secret values, such as keys, with the BN_FLG_CONSTTIME flag. Whenever a flag is checked and detected, the library changes its execution flow to SCA-secure functions that are slower but safer, protecting these secret values from being leaked. This mechanism favors performance over security, it is error-prone, and is obscure for most library developers, increasing the potential for side-channel vulnerabilities. This dissertation presents an extensive side-channel analysis of OpenSSL and criticizes its fragile flagging mechanism. This analysis reveals several flaws affecting the library resulting in multiple side-channel attacks, improved cache-timing attack techniques, and a new side channel vector. The first part of this dissertation introduces the main topic and the necessary related work, including the microarchitecture, the cache hierarchy, and attack techniques; then it presents a brief troubled history of side-channel attacks and defenses in OpenSSL, setting the stage for the related publications. This dissertation includes seven original publications contributing to the area of side-channel analysis, microarchitecture timing attacks, and applied cryptography. From an SCA perspective, the results identify several vulnerabilities and flaws enabling protocol-level attacks on RSA, DSA, and ECDSA, in addition to full SCA of the SM2 cryptosystem. With respect to microarchitecture timing attacks, the dissertation presents a new side-channel vector due to port contention in the CPU execution units. And finally, on the applied cryptography front, OpenSSL now enjoys a revamped code base securing several cryptosystems against SCA, favoring a secure-by-default protection against side-channel attacks, instead of the insecure opt-in flagging mechanism provided by the fragile BN_FLG_CONSTTIME flag