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Transactions on Cryptographic Hardware and Embedded Systems
Number of Followers: 1  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2569-2925
Published by Ruhr-Universität Bochum Homepage  [4 journals]
  • Risky Translations: Securing TLBs against Timing Side Channels

    • Authors: Florian Stolz, Jan Philipp Thoma, Pascal Sasdrich, Tim Güneysu
      Pages: 1 - 31
      Abstract: Microarchitectural side-channel vulnerabilities in modern processors are known to be a powerful attack vector that can be utilized to bypass common security boundaries like memory isolation. As shown by recent variants of transient execution attacks related to Spectre and Meltdown, those side channels allow to leak data from the microarchitecture to the observable architectural state. The vast majority of attacks currently build on the cache-timing side channel, since it is easy to exploit and provides a reliable, fine-grained communication channel. Therefore, many proposals for side-channel secure cache architectures have been made. However, caches are not the only source of side-channel leakage in modern processors and mitigating the cache side channel will inevitably lead to attacks exploiting other side channels. In this work, we focus on defeating side-channel attacks based on page translations.
      It has been shown that the Translation Lookaside Buffer (TLB) can be exploited in a very similar fashion to caches. Since the main caches and the TLB share many features in their architectural design, the question arises whether existing countermeasures against cache-timing attacks can be used to secure the TLB. We analyze state-ofthe-art proposals for side-channel secure cache architectures and investigate their applicability to TLB side channels. We find that those cache countermeasures are not
      directly applicable to TLBs, and propose TLBcoat, a new side-channel secure TLB architecture. We provide evidence of TLB side-channel leakage on RISC-V-based Linux systems, and demonstrate that TLBcoat prevents this leakage. We implement TLBcoat using the gem5 simulator and evaluate its performance using the PARSEC benchmark suite.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.1-31
  • Don’t Learn What You Already Know

    • Authors: Loïc Masure, Valence Cristiani, Maxime Lecomte, François-Xavier Standaert
      Pages: 32 - 59
      Abstract: Over the past few years, deep-learning-based attacks have emerged as a de facto standard, thanks to their ability to break implementations of cryptographic primitives without pre-processing, even against widely used counter-measures such as hiding and masking. However, the recent works of Bronchain and Standaert at Tches 2020 questioned the soundness of such tools if used in an uninformed setting to evaluate implementations protected with higher-order masking. On the opposite, worst-case evaluations may be seen as possibly far from what a real-world adversary could do, thereby leading to too conservative security bounds. In this paper, we propose a new threat model that we name scheme-aware benefiting from a trade-off between uninformed and worst-case models. Our scheme-aware model is closer to a real-world adversary, in the sense that it does not need to have access to the random nonces used by masking during the profiling phase like in a worst-case model, while it does not need to learn the masking scheme as implicitly done by an uninformed adversary. We show how to combine the power of deep learning with the prior knowledge of scheme-aware modeling. As a result, we show on simulations and experiments on public datasets how it sometimes allows to reduce by an order of magnitude the profiling complexity, i.e., the number of profiling traces needed to satisfyingly train a model, compared to a fully uninformed adversary.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.32-59
  • Adapting Belief Propagation to Counter Shuffling of NTTs

    • Authors: Julius Hermelink, Silvan Streit, Emanuele Strieder, Katharina Thieme
      Pages: 60 - 88
      Abstract: The Number Theoretic Transform (NTT) is a major building block in recently introduced lattice based post-quantum (PQ) cryptography. The NTT was target of a number of recently proposed Belief Propagation (BP)-based Side Channel Attacks (SCAs). Ravi et al. have recently proposed a number of countermeasures mitigating these attacks.
      In 2021, Hamburg et al. presented a chosen-ciphertext enabled SCA improving noise-resistance, which we use as a starting point to state our findings. We introduce a pre-processing step as well as a new factor node which we call shuffle node. Shuffle nodes allow for a modified version of BP when included into a factor graph. The node iteratively learns the shuffling permutation of fine shuffling within a BP run.
      We further expand our attacker model and describe several matching algorithms to find inter-layer connections based on shuffled measurements. Our matching algorithm allows for either mixing prior distributions according to a doubly stochastic mix matrix or to extract permutations and perform an exact un-matching of layers. We additionally discuss the usage of sub-graph inference to reduce uncertainty and improve un-shuffling of butterflies.
      Based on our results, we conclude that the proposed countermeasures of Ravi et al. are powerful and counter Hamburg et al., yet could lead to a false security perception – a powerful adversary could still launch successful attacks. We discuss on the capabilities needed to defeat shuffling in the setting of Hamburg et al. using our expanded attacker model.
      Our methods are not limited to the presented case but provide a toolkit to analyze and evaluate shuffling countermeasures in BP-based attack scenarios.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.60-88
  • Find the Bad Apples: An efficient method for perfect key recovery under
           imperfect SCA oracles – A case study of Kyber

    • Authors: Muyan Shen, Chi Cheng, Xiaohan Zhang, Qian Guo, Tao Jiang
      Pages: 89 - 112
      Abstract: Side-channel resilience is a crucial feature when assessing whether a postquantum cryptographic proposal is sufficiently mature to be deployed. In this paper, we propose a generic and efficient adaptive approach to improve the sample complexity (i.e., the required number of traces) of plaintext-checking (PC) oracle-based sidechannel attacks (SCAs), a major class of key recovery chosen-ciphertext SCAs on lattice-based key encapsulation mechanisms (KEMs). This new approach is preferable when the constructed PC oracle is imperfect, which is common in practice, and its basic idea is to design new detection codes that can determine erroneous positions in the initially recovered secret key. These secret entries are further corrected with a small number of additional traces. This work benefits from the generality of PC oracle and thus is applicable to various schemes and implementations.
      Our main target is Kyber since it has been selected by NIST as the KEM algorithm for standardization. We instantiated the proposed generic attack on Kyber512 and then conducted extensive computer simulations against Kyber512 and FireSaber. We further mounted an electromagnetic (EM) attack against an optimized implementation of Kyber512 in the pqm4 library running on an STM32F407G board with an ARM Cortex-M4 microcontroller. These simulations and real-world experiments demonstrate that the newly proposed attack could greatly improve the state-of-the-art in terms of the required number of traces. For instance, the new attack requires only 41% of the EM traces needed in a majority-voting attack in our experiments, where the raw oracle accuracy is fixed.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.89-112
  • Low-Latency and Low-Randomness Second-Order Masked Cubic Functions

    • Authors: Aein Rezaei Shahmirzadi, Siemen Dhooghe, Amir Moradi
      Pages: 113 - 152
      Abstract: Masking schemes are the most popular countermeasure to mitigate Side-Channel Analysis (SCA) attacks. Compared to software, their hardware implementations require certain considerations with respect to physical defaults, such as glitches. To counter this extended leakage effect, the technique known as Threshold Implementation (TI) has proven to be a reliable solution. However, its efficiency, namely the number of shares, is tied to the algebraic degree of the target function. As a result, the application of TI may lead to unaffordable implementation costs. This dependency is relaxed by the successor schemes where the minimum number of d + 1 shares suffice for dth-order protection independent of the function’s algebraic degree. By this, although the number of input shares is reduced, the implementation costs are not necessarily low due to their high demand for fresh randomness. It becomes even more challenging when a joint low-latency and low-randomness cost is desired. In this work, we provide a methodology to realize the second-order glitch-extended probing-secure implementation of cubic functions with three shares while allowing to reuse fresh randomness. This enables us to construct low-latency second-order secure implementations of several popular lightweight block ciphers, including Skinny, Midori, and Prince, with a very limited number of fresh masks. Notably, compared to state-of-the-art equivalent implementations, our designs lower the latency in terms of the number of clock cycles while keeping randomness costs low.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.113-152
  • High-order Polynomial Comparison and Masking Lattice-based Encryption

    • Authors: Jean-Sébastien Coron, François Gérard, Simon Montoya, Rina Zeitoun
      Pages: 153 - 192
      Abstract: The main protection against side-channel attacks consists in computing every function with multiple shares via the masking countermeasure. For IND-CCA secure lattice-based encryption schemes, the masking of the decryption algorithm requires the high-order computation of a polynomial comparison. In this paper, we describe and evaluate a number of different techniques for such high-order comparison, always with a security proof in the ISW probing model. As an application, we describe the full high-order masking of the NIST standard Kyber, with a concrete implementation on ARM Cortex M architecture, and a t-test evaluation.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.153-192
  • RISC-V Instruction Set Extensions for Lightweight Symmetric Cryptography

    • Authors: Hao Cheng, Johann Großschädl, Ben Marshall, Dan Page, Thinh Pham
      Pages: 193 - 237
      Abstract: The NIST LightWeight Cryptography (LWC) selection process aims to standardise cryptographic functionality which is suitable for resource-constrained devices. Since the outcome is likely to have significant, long-lived impact, careful evaluation of each submission with respect to metrics explicitly outlined in the call is imperative. Beyond the robustness of submissions against cryptanalytic attack, metrics related to their implementation (e.g., execution latency and memory footprint) form an important example. Aiming to provide evidence allowing richer evaluation with respect to such metrics, this paper presents the design, implementation, and evaluation of one separate Instruction Set Extension (ISE) for each of the 10 LWC final round submissions, namely Ascon, Elephant, GIFT-COFB, Grain-128AEADv2, ISAP, PHOTON-Beetle, Romulus, Sparkle, TinyJAMBU, and Xoodyak; although we base the work on use of RISC-V, we argue that it provides more general insight.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.193-237
  • High Order Side-Channel Security for Elliptic-Curve Implementations

    • Authors: Sonia Belaïd, Matthieu Rivain
      Pages: 238 - 276
      Abstract: Elliptic-curve implementations protected with state-of-the-art countermeasures against side-channel attacks might still be vulnerable to advanced attacks that recover secret information from a single leakage trace. The effectiveness of these attacks is boosted by the emergence of deep learning techniques for side-channel analysis which relax the control or knowledge an adversary must have on the target implementation. In this paper, we provide generic countermeasures to withstand these attacks for a wide range of regular elliptic-curve implementations. We first introduce a framework to formally model a regular algebraic program which consists of a sequence of algebraic operations indexed by key-dependent values. We then introduce a generic countermeasure to protect these types of programs against advanced single-trace side-channel attacks. Our scheme achieves provable security in the noisy leakage model under a formal assumption on the leakage of randomized variables. To demonstrate the applicability of our solution, we provide concrete examples on several widely deployed scalar multiplication algorithms and report some benchmarks for a protected implementation on a smart card.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.238-276
  • MCRank: Monte Carlo Key Rank Estimation for Side-Channel Security

    • Authors: Giovanni Camurati, Matteo Dell’Amico, François-Xavier Standaert
      Pages: 277 - 300
      Abstract: Key rank estimation provides a measure of the effort that the attacker has to spend bruteforcing the key of a cryptographic algorithm, after having gained some information from a side channel attack. We present MCRank, a novel method for key rank estimation based on Monte Carlo sampling. MCRank provides an unbiased estimate of the rank and a confidence interval. Its bounds rapidly become tight for increasing sample size, with a corresponding linear increase of the execution time. When applied to evaluate an AES-128 implementation, MCRank can be orders of magnitude faster than the state-of-the-art histogram-based enumeration method for comparable bound tightness. It also scales better than previous work for large keys, up to 2048 bytes. Besides its conceptual simplicity and efficiency, MCRank can assess for the first time the security of large keys even if the probability distributions given the side channel leakage are not independent between subkeys, which occurs, for example, when evaluating the leakage security of an AES-256 implementation.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.277-300
  • ImpedanceVerif: On-Chip Impedance Sensing for System-Level Tampering

    • Authors: Tahoura Mosavirik, Patrick Schaumont, Shahin Tajik
      Pages: 301 - 325
      Abstract: Physical attacks can compromise the security of cryptographic devices. Depending on the attack’s requirements, adversaries might need to (i) place probes in the proximity of the integrated circuits (ICs) package, (ii) create physical connections between their probes/wires and the system’s PCB, or (iii) physically tamper with the PCB’s components, chip’s package, or substitute the entire PCB to prepare the device for the attack. While tamper-proof enclosures prevent and detect physical access to the system, their high manufacturing cost and incompatibility with legacy systems make them unattractive for many low-cost scenarios. In this paper, inspired by methods known from the field of power integrity analysis, we demonstrate how the impedance characterization of the system’s power distribution network (PDN) using on-chip circuit-based network analyzers can detect various classes of tamper events. We explain how these embedded network analyzers, without any modifications to the system, can be deployed on FPGAs to extract the frequency response of the PDN. The analysis of these frequency responses reveals different classes of tamper events from board to chip level. To validate our claims, we run an embedded network analyzer on FPGAs of a family of commercial development kits and perform extensive measurements for various classes of PCB and IC package tampering required for conducting different side-channel or fault attacks. Using the Wasserstein Distance as a statistical metric, we further show that we can confidently detect tamper events. Our results, interestingly, show that even environment-level tampering activities, such as the proximity of contactless EM probes to the IC package or slightly polished IC package, can be detected using on-chip impedance sensing.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.301-325
  • BipBip: A Low-Latency Tweakable Block Cipher with Small Dimensions

    • Authors: Yanis Belkheyar, Joan Daemen, Christoph Dobraunig, Santosh Ghosh, Shahram Rasoolzadeh
      Pages: 326 - 368
      Abstract: Recently, a memory safety concept called Cryptographic Capability Computing (C3) has been proposed. C3 is the first memory safety mechanism that works without requiring extra storage for metadata and hence, has the potential to significantly enhance the security of modern IT-systems at a rather low cost. To achieve this, C3 heavily relies on ultra-low-latency cryptographic primitives. However, the most crucial primitive required by C3 demands uncommon dimensions. To partially encrypt 64-bit pointers, a 24-bit tweakable block cipher with a 40-bit tweak is needed. The research on low-latency tweakable block ciphers with such small dimensions is not very mature. Therefore, designing such a cipher provides a great research challenge, which we take on with this paper. As a result, we present BipBip, a 24-bit tweakable block cipher with a 40-bit tweak that allows for ASIC implementations with a latency of 3 cycles at a 4.5 GHz clock frequency on a modern 10 nm CMOS technology.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.326-368
  • Higher-Order DCA Attacks on White-Box Implementations with Masking and
           Shuffling Countermeasures

    • Authors: Yufeng Tang, Zheng Gong, Jinhai Chen, Nanjiang Xie
      Pages: 369 - 400
      Abstract: On white-box implementations, it has been proven that differential computation analysis (DCA) can recover secret keys without time-costly reverse engineering. At CHES 2021, Seker et al. combined linear and non-linear masking protections (SEL masking) to prevent sensitive variables from being predicted by DCA. At Eurocrypt 2021, Biryukov and Udovenko introduced a public dummy shuffling construction (BU shuffling) to protect sensitive functions. In this paper, we extend higher-order DCA (HO-DCA) to higher-degree context for exploiting the vulnerabilities against the state-of-the-art countermeasures. The data-dependency HO-DCA (DDHO-DCA), which is proposed at CHES 2020, is improved to successfully recover the correct key of SEL masking. In specific, our improved DDHO-DCA can also enhance the attack result of #100 which is the third winning challenge in WhibOx 2019. Since the XOR phase plays the same role as linear masking, we prove that a specific BU shuffling is vulnerable to HO-DCA attacks. Furthermore, we demonstrate that the combination of SEL masking and the specific BU shuffling still cannot defeat our higher-degree HO-DCA and improved DDHO-DCA attacks.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.369-400
  • Information Theory-based Evolution of Neural Networks for Side-channel

    • Authors: Rabin Y. Acharya, Fatemeh Ganji, Domenic Forte
      Pages: 401 - 437
      Abstract: Profiled side-channel analysis (SCA) leverages leakage from cryptographic implementations to extract the secret key. When combined with advanced methods in neural networks (NNs), profiled SCA can successfully attack even those cryptocores assumed to be protected against SCA. Despite the rise in the number of studies devoted to NN-based SCA, a range of questions has remained unanswered, namely: how to choose an NN with an adequate configuration, how to tune the NN’s hyperparameters, when to stop the training, etc. Our proposed approach, “InfoNEAT,” tackles these issues in a natural way. InfoNEAT relies on the concept of neural structure search, enhanced by information-theoretic metrics to guide the evolution, halt it with novel stopping criteria, and improve time-complexity and memory footprint. The performance of InfoNEAT is evaluated by applying it to publicly available datasets composed of real side-channel measurements. In addition to the considerable advantages regarding the automated configuration of NNs, InfoNEAT demonstrates significant improvements over other approaches for effective key recovery in terms of the number of epochs (e.g.,x6 faster) and the number of attack traces compared to both MLPs and CNNs (e.g., up to 1000s fewer traces to break a device) as well as a reduction in the number of trainable parameters compared to MLPs (e.g., by the factor of up to 32). Furthermore, through experiments, it is demonstrated that InfoNEAT’s models are robust against noise and desynchronization in traces.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.401-437
  • Low-Latency Design and Implementation of the Squaring in Class Groups for
           Verifiable Delay Function Using Redundant Representation

    • Authors: Danyang Zhu, Rongrong Zhang, Lun Ou, Jing Tian, Zhongfeng Wang
      Pages: 438 - 462
      Abstract: A verifiable delay function (VDF) is a function whose evaluation requires running a prescribed number of sequential steps over a group while the result can be efficiently verified. As a kind of cryptographic primitives, VDFs have been adopted in rapidly growing applications for decentralized systems. For the security of VDFs in practical applications, it is widely agreed that the fastest implementation for the VDF evaluation, sequential squarings in a group of unknown order, should be publicly provided. To this end, we propose a possible minimum latency hardware implementation for the squaring in class groups by algorithmic and architectural level co-optimization. Firstly, low-latency architectures for large-number division, multiplication, and addition are devised using redundant representation, respectively. Secondly, we present two hardware-friendly algorithms which avoid time-consuming divisions involved in calculations related to the extended greatest common divisor (XGCD) and design the corresponding low-latency architectures. Besides, we schedule and reuse these computation modules to achieve good resource utilization by using compact instruction control. Finally, we code and synthesize the proposed design under the TSMC 28nm CMOS technology. The experimental results show that our design can achieve a speedup of 3.6x compared to the state-of-the-art implementation of the squaring in the class group. Moreover, compared to the optimal C++ implementation over an advanced CPU, our implementation is 9.1x faster.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.438-462
  • Medha: Microcoded Hardware Accelerator for computing on Encrypted Data

    • Authors: Ahmet Can Mert, Aikata, Sunmin Kwon, Youngsam Shin, Donghoon Yoo, Yongwoo Lee, Sujoy Sinha Roy
      Pages: 463 - 500
      Abstract: Homomorphic encryption enables computation on encrypted data, and hence it has a great potential in privacy-preserving outsourcing of computations to the cloud. Hardware acceleration of homomorphic encryption is crucial as software implementations are very slow. In this paper, we present design methodologies for building a programmable hardware accelerator for speeding up the cloud-side homomorphic evaluations on encrypted data.
      First, we propose a divide-and-conquer technique that enables homomorphic evaluations in the polynomial ring RQ,2N = ZQ[x]/(x2N + 1) to use a hardware accelerator that has been built for the smaller ring RQ,N = ZQ[x]/(xN + 1). The technique makes it possible to use a single hardware accelerator flexibly for supporting several homomorphic encryption parameter sets.
      Next, we present several architectural design methods that we use to realize the flexible and instruction-set accelerator architecture, which we call ‘Medha’. At every level of the implementation hierarchy, we explore possibilities for parallel processing. Starting from hardware-friendly parallel algorithms for the basic building blocks, we gradually build heavily parallel RNS polynomial arithmetic units. Next, many of these parallel units are interconnected elegantly so that their interconnections require the minimum number of nets, therefore making the overall architecture placement-friendly on the platform. As homomorphic encryption is computation- as well as data-centric, the speed of homomorphic evaluations depends greatly on the way the data variables are handled. For Medha, we take a memory-conservative design approach and get rid of any off-chip memory access during homomorphic evaluations.
      Finally, we implement Medha in a Xilinx Alveo U250 FPGA and measure timing performances of the microcoded homomorphic addition, multiplication, key-switching, and rescaling routines for the leveled fully homomorphic encryption scheme RNSHEAAN at 200 MHz clock frequency. For the large parameter sets (log Q,N) = (438, 214) and (546, 215), Medha achieves accelerations by up to 68× and 78× times respectively compared to a highly optimized software implementation Microsoft SEAL running at 2.3 GHz.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.463-500
  • FDFB: Full Domain Functional Bootstrapping Towards Practical Fully
           Homomorphic Encryption

    • Authors: Kamil Kluczniak, Leonard Schild
      Pages: 501 - 537
      Abstract: Computation on ciphertexts of all known fully homomorphic encryption (FHE) schemes induces some noise, which, if too large, will destroy the plaintext. Therefore, the bootstrapping technique that re-encrypts a ciphertext and reduces the noise level remains the only known way of building FHE schemes for arbitrary unbounded computations. The bootstrapping step is also the major efficiency bottleneck in current FHE schemes. A promising direction towards improving concrete efficiency is to exploit the bootstrapping process to perform useful computation while reducing the noise at the same time. We show a bootstrapping algorithm, which embeds a lookup table and evaluates arbitrary functions of the plaintext while reducing the noise. Depending on the choice of parameters, the resulting homomorphic encryption scheme may be either an exact FHE or homomorphic encryption for approximate arithmetic. Since we can evaluate arbitrary functions over the plaintext space, we can use the natural homomorphism of Regev encryption to compute affine functions without bootstrapping almost for free. Consequently, our algorithms are particularly suitable for arithmetic circuits over a finite field with many additions and scalar multiplication gates. We achieve significant speedups when compared to binary circuit-based FHE. For example, we achieve 280-1200x speedups when computing an affine function of size 784 followed by any univariate function when compared to FHE schemes that compute binary circuits. With our bootstrapping algorithm, we can efficiently convert between arithmetic and boolean plaintexts and extend the plaintext space using the Chinese remainder theorem. Furthermore, we can run the computation in an exact and approximate mode where we trade-off the size of the plaintext space with approximation error. We provide a tight error analysis and show several parameter sets for our bootstrapping. Finally, we implement our algorithm and provide extensive tests. We demonstrate our algorithms by evaluating different neural networks in several parameter and accuracy settings.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.501-537
  • A Faster Third-Order Masking of Lookup Tables

    • Authors: Anju Alexander, Annapurna Valiveti, Srinivas Vivek
      Pages: 538 - 556
      Abstract: Masking of S-boxes using lookup tables is an effective countermeasure to thwart side-channel attacks on block ciphers implemented in software. At first and second orders, the Table-based Masking (TBM) schemes can be very efficient and even faster than circuit-based masking schemes. Ever since the customised second-order TBM schemes were proposed, the focus has been on designing and optimising Higher-Order Table-based Masking (HO-TBM) schemes that facilitate masking at arbitrary order. One of the reasons for this trend is that at large orders HO-TBM schemes are significantly slower and consume a prohibitive amount of RAM memory compared to circuit-based masking schemes such as bit-sliced masking, and hence efforts were targeted in this direction. However, a recent work due to Valiveti and Vivek (TCHES 2021) has demonstrated that the HO-TBM scheme of Coron et al. (TCHES 2018) is feasible to be implemented on memory-constrained devices with pre-processing capability and a competitive online execution time. Yet, currently, there are no customised designs for third-order TBM that are more efficient than instantiating a HO-TBM scheme at third order.
      In this work, we propose a third-order TBM scheme for arbitrary S-boxes that is secure in the probing model and under compositions, i.e., 3-SNI secure. It is very efficient in terms of the overall running time, compared to the third-order instantiations of state-of-the-art HO-TBM schemes. It also supports the pre-processing functionality. For example, the overall running time of a single execution of the third-order masked AES-128 on a 32-bit ARM-Cortex M4 micro-controller is reduced by about 80% without any overhead on the online execution time. This implies that the online execution time of the proposed scheme is approximately eight times faster than the bit-sliced masked implementation at third order, and it is comparable to the recent scheme of Wang et al. (TCHES 2022) that makes use of reuse of shares. We also present the implementation results for the third-order masked PRESENT cipher. Our work suggests that there is a significant scope for tuning the performance of HO-TBM schemes at lower orders.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.538-556
  • SoK: SCA-secure ECC in software – mission impossible'

    • Authors: Lejla Batina, Łukasz Chmielewski, Björn Haase, Niels Samwel, Peter Schwabe
      Pages: 557 - 589
      Abstract: This paper describes an ECC implementation computing the X25519 keyexchange protocol on the Arm Cortex-M4 microcontroller. For providing protections against various side-channel and fault attacks we first review known attacks and countermeasures, then we provide software implementations that come with extensive mitigations, and finally we present a preliminary side-channel evaluation. To our best knowledge, this is the first public software claiming affordable protection against multiple classes of attacks that are motivated by distinct real-world application scenarios. We distinguish between X25519 with ephemeral keys and X25519 with static keys and show that the overhead to our baseline unprotected implementation is about 37% and 243%, respectively. While this might seem to be a high price to pay for security, we also show that even our (most protected) static implementation is at least as efficient as widely-deployed ECC cryptographic libraries, which offer much less protection.
      PubDate: 2022-11-29
      DOI: 10.46586/tches.v2023.i1.557-589
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