IACR News
Updates on the COVID-19 situation are on the
Announcement channel.
Here you can see all recent updates to the IACR webpage. These updates are also available:
25 May 2023
Quentin L. Meunier, Abdul Rahman Taleb
Side-Channel Attacks are powerful attacks which can recover secret information in a cryptographic device by analysing physical quantities such as power consumption. Masking is a common countermeasure to these attacks which can be applied in software and hardware, and consists in splitting the secrets in several parts. Masking schemes and their implementations are often not trivial, and require the use of automated tools to check for their correctness.
In this work, we propose a new practical tool named VerifMSI which extends an existing verification tool called LeakageVerif targeting software schemes. Compared to LeakageVerif, VerifMSI includes hardware constructs, namely gates and registers, what allows to take glitch propagation into account. Moreover, it includes a new representation of the inputs, making it possible to verify three existing security properties (Non-Interference, Strong Non-Interference, Probe Isolating Non-Interference) as well as a newly defined one called Relaxed Non-Interference, compared to the unique Threshold Probing Security verified in LeakageVerif. Finally, optimisations have been integrated in VerifMSI in order to speed up the verification.
We evaluate VerifMSI on a set of 9 benchmarks from the literature, focusing on the hardware descriptions, and show that it performs well both in terms of accuracy and scalability.
Bo-Yin Yang, Wei-Jeng Wang, Shang-Yi Yang, Char-Shin Miou, Chen-Mou Cheng
Solving multivariate polynomial systems over finite fields is an important
problem in cryptography. For random F2 low-degree systems with equally many
variables and equations, enumeration is more efficient than advanced solvers for all
practical problem sizes. Whether there are others remained an open problem.
We here study and propose an exhaustive-search algorithm for low degrees systems
over F3 which is suitable for parallelization. We implemented it on Graphic Processing
Units (GPUs) and commodity CPUs. Its optimizations and differences from the F2
case are also analyzed.
We can solve 30+ quadratic equations in 30 variables on an NVIDIA GeForce GTX
980 Ti in 14 minutes; a cubic system takes 36 minutes. This well outperforms
existing solvers. Using these results, we compare Gröbner Bases vs. enumeration for
polynomial systems over small fields as the sizes go up.
22 May 2023
Graz, Austria, 1 September - 4 September 2023
Event date: 1 September to 4 September 2023
Warszawa, Polska, 31 July - 3 August 2023
Event date: 31 July to 3 August 2023
Anubhab Baksi
In the design of GIFT, half round key XOR is used. This leads to the undesired consequence that the security against the differential/linear attacks are overestimated. This comes from the observation that; in the usual DDT/LAT based analysis of the differential/linear attacks, the inherent assumption is the full round key is XORed at each round.
Yang Yu, Huiwen Jia, Xiaoyun Wang
Lattice gadgets and the associated algorithms are the essential building blocks of lattice-based cryptography. In the past decade, they have been applied to build versatile and powerful cryptosystems. However, the practical optimizations and designs of gadget-based schemes generally lag their theoretical constructions.
For example, the gadget-based signatures have elegant design and capability of extending to more advanced primitives, but they are far less efficient than other lattice-based signatures.
This work aims to improve the practicality of gadget-based cryptosystems, with a focus on hash-and-sign signatures. To this end, we develop a compact gadget framework in which the used gadget is a square matrix instead of the short and fat one used in previous constructions. To work with this compact gadget, we devise a specialized gadget sampler, called semi-random sampler, to compute the approximate preimage. It first deterministically computes the error and then randomly samples the preimage. We show that for uniformly random targets, the preimage and error distributions are simulatable without knowing the trapdoor. This ensures the security of the signature applications. Compared to the Gaussian-distributed errors in previous algorithms, the deterministic errors have a smaller size, which lead to a substantial gain in security and enables a practically working instantiation.
As the applications, we present two practically efficient gadget-based signature schemes based on NTRU and Ring-LWE respectively. The NTRU-based scheme offers comparable efficiency to Falcon and Mitaka and a simple implementation without the need of generating the NTRU trapdoor. The LWE-based scheme also achieves a desirable overall performance. It not only greatly outperforms the state-of-the-art LWE-based hash-and-sign signatures, but also has an even smaller size than the LWE-based Fiat-Shamir signature scheme Dilithium. These results fill the long-term gap in practical gadget-based signatures.
This work aims to improve the practicality of gadget-based cryptosystems, with a focus on hash-and-sign signatures. To this end, we develop a compact gadget framework in which the used gadget is a square matrix instead of the short and fat one used in previous constructions. To work with this compact gadget, we devise a specialized gadget sampler, called semi-random sampler, to compute the approximate preimage. It first deterministically computes the error and then randomly samples the preimage. We show that for uniformly random targets, the preimage and error distributions are simulatable without knowing the trapdoor. This ensures the security of the signature applications. Compared to the Gaussian-distributed errors in previous algorithms, the deterministic errors have a smaller size, which lead to a substantial gain in security and enables a practically working instantiation.
As the applications, we present two practically efficient gadget-based signature schemes based on NTRU and Ring-LWE respectively. The NTRU-based scheme offers comparable efficiency to Falcon and Mitaka and a simple implementation without the need of generating the NTRU trapdoor. The LWE-based scheme also achieves a desirable overall performance. It not only greatly outperforms the state-of-the-art LWE-based hash-and-sign signatures, but also has an even smaller size than the LWE-based Fiat-Shamir signature scheme Dilithium. These results fill the long-term gap in practical gadget-based signatures.
Kevin Choi, Aathira Manoj, Joseph Bonneau
Motivated and inspired by the emergence of blockchains, many new protocols have recently been proposed for generating publicly verifiable randomness in a distributed yet secure fashion. These protocols work under different setups and assumptions, use various cryptographic tools, and entail unique trade-offs and characteristics. In this paper, we systematize the design of distributed randomness beacons (DRBs) as well as the cryptographic building blocks they rely on. We evaluate protocols on two key security properties, unbiasability and unpredictability, and discuss common attack vectors for predicting or biasing the beacon output and the countermeasures employed by protocols. We also compare protocols by communication and computational efficiency. Finally, we provide insights on the applicability of different protocols in various deployment scenarios and highlight possible directions for further research.
Marwan Zeggari, Aydin Abadi, Renaud Lambiotte, Mohamad Kassab
Sneakers were designated as the most counterfeited fashion item online, with three times more risk in a trade than any other fashion purchase. As the market expands, the current sneaker scene displays several vulnerabilities and trust flaws, mostly related to the legitimacy of assets or actors. In this paper, we investigate various blockchain-based mechanisms to address these large-scale trust issues. We argue that (i) pre-certified and tracked assets through the use of non-fungible tokens can ensure the genuine nature of an asset and authenticate its owner more effectively during peer-to-peer trading across a marketplace; (ii) a game-theoretic-based system with economic incentives for participating users can greatly reduce the rate of online fraud and address missed delivery deadlines; (iii) a decentralized dispute resolution system biased in favour of an honest party can solve potential conflicts more reliably.
Zhengjun Cao, Lihua Liu
We show that the key agreement scheme [Internet of Things, 2022(18): 100493] is flawed. (1) It neglects the structure of an elliptic curve and presents some false computations. (2) The scheme is insecure against key compromise impersonation attack.
Christof Beierle, Patrick Felke, Gregor Leander, Patrick Neumann, Lukas Stennes
Recent constructions of (tweakable) block ciphers with an embedded cryptographic backdoor relied on the existence of probability-one differentials or perfect (non-)linear approximations over a reduced-round version of the primitive. In this work, we study how the existence of probability-one differentials or perfect linear approximations over two rounds of a substitution-permutation network can be avoided by design. More precisely, we develop criteria on the s-box and the linear layer that guarantee the absence of probability-one differentials for all keys. We further present an algorithm that allows to efficiently exclude the existence of keys for which there exists a perfect linear approximation.
Lichao Wu, Guilherme Perin, Stjepan Picek
The ASCADv2 dataset ranks among the most secure publicly available datasets today. Two layers of countermeasures protect it: affine masking and shuffling, and the current attack approaches rely on strong assumptions. Specifically, besides having access to the source code, an adversary also requires prior knowledge of random shares. This paper forgoes reliance on such knowledge and proposes two attack approaches based on the vulnerabilities of the affine mask implementation. As a result, the first attack can retrieve all secret keys' reliance in less than a minute. Although the second attack is not entirely successful in recovering all keys, we believe more traces would help make such an attack fully functional.
Giuseppe D'Alconzo, Andrea Flamini, Andrea Gangemi
Group actions are becoming a viable option for post-quantum cryptography assumptions. Indeed, in recent years some works have shown how to construct primitives from assumptions based on isogenies of elliptic curves, such as CSIDH, on tensors or on code equivalence problems. This paper presents a bit commitment scheme, built on non-transitive group actions, which is shown to be secure in the standard model, under the decisional Group Action Inversion Problem. In particular, the commitment is computationally hiding and perfectly binding, and is obtained from a novel and general framework that exploits the properties of some orbit-invariant functions, together with group actions. Previous constructions depend on an interaction between the sender and the receiver in the commitment phase, which results in an interactive bit commitment. We instead propose the first non-interactive bit commitment based on group actions. Then we show that, when the sender is honest, the constructed commitment enjoys an additional feature, i.e., it is possible to tell whether two commitments were obtained from the same input, without revealing the input. We define the security properties that such a construction must satisfy, and we call this primitive linkable commitment. Finally, as an example, an instantiation of the scheme using tensors with coefficients in a finite field is provided. In this case, the invariant function is the computation of the rank of a tensor, and the cryptographic assumption is related to the Tensor Isomorphism problem.
Mugurel Barcau, Vicentiu Pasol, George C Turcas
The present work builds on previous investigations of the authors (and their collaborators) regarding bridges, a certain type of morphisms between encryption schemes, making a step forward in developing a (category theory) language for studying relations between encryption schemes. Here we analyse the conditions under which bridges can be performed sequentially, formalizing the notion of composability. One of our results gives a sufficient condition for a pair of bridges to be composable. We illustrate that composing two bridges, each independently satisfying a previously established IND-CPA security definition, can actually lead to an insecure bridge. Our main result gives a sufficient condition that a pair of secure composable bridges should satisfy in order for their composition to be a secure bridge. We also introduce the concept of a complete bridge and show that it is connected to the notion of Fully composable Homomorphic Encryption (FcHE), recently considered by Micciancio. Moreover, we show that a result of Micciancio which gives a construction of FcHE schemes can be phrased in the language of complete bridges, where his insights can be formalised in a greater generality.
Supriya Adhikary, Angshuman Karmakar
With the increased use of data and communication through the internet and the abundant misuse of personal data by many organizations, people are more sensitive about their privacy. Privacy-preserving computation is becoming increasingly important in this era. Functional encryption allows a user to evaluate a function on encrypted data without revealing sensitive information. Most implementations of functional encryption schemes are too time-consuming for practical use. Mera et al. first proposed an inner product functional encryption scheme based on ring learning with errors to improve efficiency. In this work, we optimize the implementation of their work and propose a fast inner product functional encryption library. Specifically, we identify the main performance bottleneck, which is the number theoretic transformation based polynomial multiplication used in the scheme. We also identify the micro and macro level parallel components of the scheme and propose novel techniques to improve the efficiency using $\textit{open multi-processing}$ and $\textit{advanced vector extensions 2}$ vector processor. Compared to the original implementation, our optimization methods translate to $89.72\%$, $83.06\%$, $59.30\%$, and $53.80\%$ improvements in the $\textbf{Setup}$, $\textbf{Encrypt}$, $\textbf{KeyGen}$, and $\textbf{Decrypt}$ operations respectively, in the scheme for standard security level. Designing privacy-preserving applications using functional encryption is ongoing research. Therefore, as an additional contribution to this work, we design a privacy-preserving biometric authentication scheme using inner product functional encryption primitives.
Tung Le, Rouzbeh Behnia, Jorge Guajardo, Thang Hoang
Searchable encrypted systems enable privacy-preserving keyword search on encrypted data. Symmetric Searchable Encryption (SSE) achieves high security (e.g., forward privacy) and efficiency (i.e., sublinear search), but it only supports single-user. Public Key Searchable Encryption (PEKS) supports multi-user settings, however, it suffers from inherent security limitations such as being vulnerable to keyword-guessing attacks and the lack of forward privacy. Recent work has combined SSE and PEKS to achieve the best of both worlds: support multi-user settings, provide forward privacy while having sublinear complexity. However, despite their elegant design, the existing hybrid scheme inherits some of the security limitations of the underlying paradigms (e.g., patterns leakage, keyword-guessing) and might not be suitable for certain applications due to costly public-key operations (e.g., bilinear pairing). In this paper, we propose MUSES, a new multi-user encrypted search scheme that addresses the limitations in the existing hybrid design, while offering user efficiency. Specifically, MUSES permits multi-user functionalities (reader/writer separation, permission revocation), prevents keyword-guessing attacks, protects search/result patterns, achieves forward/backward privacy, and features minimal user overhead. In MUSES, we demonstrate a unique incorporation of various state-of-the-art distributed cryptographic protocols including Distributed Point Function, Distributed PRF, and Secret-Shared Shuffle. We also introduce a new oblivious shuffle protocol for the general ?-party setting with dishonest majority, which can be of independent interest. Our experimental results indicated that the keyword search in our scheme is two orders of magnitude faster with 13× lower user bandwidth overhead than the state-of-the-art.
Erkan Tairi, Akın Ünal
Functional encryption (FE) is a primitive where the holder of a master secret key can control which functions a user can evaluate on encrypted data. It is a powerful primitive that even implies indistinguishability obfuscation (iO), given sufficiently compact ciphertexts (Ananth-Jain, CRYPTO'15 and Bitansky-Vaikuntanathan, FOCS'15). However, despite being extensively studied, there are FE schemes, such as function-hiding inner-product FE (Bishop-Jain-Kowalczyk, AC'15, Abdalla-Catalano-Fiore-Gay-Ursu, CRYPTO’18) and compact quadratic FE (Baltico-Catalano-Fiore-Gay, Lin, CRYPTO’17), that can be only realized using pairings. This raises whether there are some mathematical barriers which hinder us from realizing these FE schemes from other assumptions.
In this paper, we study the difficulty of constructing lattice-based compact FE. We generalize the impossibility results of Ünal (EC'20) for lattice-based function-hiding FE, and extend it to the case of compact FE. Concretely, we prove lower bounds for lattice-based compact FE schemes which meet some (natural) algebraic restrictions at encryption and decryption, and have messages and ciphertexts of constant dimensions. We see our results as important indications of why it is hard to construct lattice-based FE schemes for new functionalities, and which mathematical barriers have to be overcome.
In this paper, we study the difficulty of constructing lattice-based compact FE. We generalize the impossibility results of Ünal (EC'20) for lattice-based function-hiding FE, and extend it to the case of compact FE. Concretely, we prove lower bounds for lattice-based compact FE schemes which meet some (natural) algebraic restrictions at encryption and decryption, and have messages and ciphertexts of constant dimensions. We see our results as important indications of why it is hard to construct lattice-based FE schemes for new functionalities, and which mathematical barriers have to be overcome.
Giacomo Borin, Edoardo Persichetti, Paolo Santini
In this work, we describe a technique to amplify the soundness of zero-knowledge proofs of knowledge for cryptographic group actions.
Felice Manganiello, Freeman Slaughter
This paper introduces a new family of CVE schemes built from generic errors (GE-CVE) and identifies a vulnerability therein. To introduce the problem, we generalize the concept of error sets beyond those defined by a metric, and use the set-theoretic difference operator to characterize when these error sets are detectable or correctable by codes. We prove the existence of a general, metric-less form of the Gilbert-Varshamov bound, and show that - like in the Hamming setting - a random code corrects a generic error set with overwhelming probability. We define the generic error SDP (GE-SDP), which is contained in the complexity class of NP-hard problems, and use its hardness to demonstrate the security of GE-CVE. We prove that these schemes are complete, sound, and zero-knowledge. Finally, we identify a vulnerability of the GE-SDP for codes defined over large extension fields and without a very high rate. We show that certain GE-CVE parameters suffer from this vulnerability, notably the restricted CVE scheme.
Malik Imran, Aikata Aikata, Sujoy Sinha Roy, Samuel pagliarini
In this brief, we realize different architectural techniques towards improving the performance of post-quantum cryptography (PQC) algorithms when implemented as hardware accelerators on an application-specific integrated circuit (ASIC) platform. Having SABER as a case study, we designed a 256-bit wide architecture geared for high-speed cryptographic applications that incorporates smaller and distributed SRAM memory blocks. Moreover, we have adapted the building blocks of SABER to process 256-bit words. We have also used a buffer technique for efficient polynomial coefficient multiplications to reduce the clock cycle count. Finally, double-sponge functions are combined serially (one after another) in a high-speed KECCAK core to improve the hash operations of SHA/SHAKE. For key-generation, encapsulation, and decapsulation operations of SABER, our 256-bit wide accelerator with a single sponge function is 1.71x, 1.45x, and 1.78x faster compared to the raw clock cycle count of a serialized SABER design. Similarly, our 256-bit implementation with double-sponge functions takes 1.08x, 1.07x & 1.06x fewer clock cycles compared to its single-sponge counterpart. The studied optimization techniques are not specific to SABER - they can be utilized for improving the performance of other lattice-based PQC accelerators.
Fuchun Guo, Willy Susilo, Xiaofeng Chen, Peng Jiang, Jianchang Lai, Zhen Zhao
Proposing novel cryptography schemes (e.g., encryption, signatures, and protocols) is one of the main research goals in modern cryptography. In this paper, based on more than 800 research papers since 1976 that we have surveyed, we introduce the research philosophy of cryptography behind these papers. We use ``benefits" and ``novelty" as the keywords to introduce the research philosophy of proposing new schemes, assuming that there is already one scheme proposed for a cryptography notion. Next, we introduce how benefits were explored in the literature and we have categorized the methodology into 3 ways for benefits, 6 types of benefits, and 17 benefit areas. As examples, we introduce 40 research strategies within these benefit areas that were invented in the literature. The introduced research strategies have covered most cryptography schemes published in top-tier cryptography conferences.