IACR News
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24 May 2024
Changrui Mu, Prashant Nalini Vasudevan
We investigate the properties and power of such instance-hiding proofs, and show the following: 1. Any language with an IHIP is contained in AM/poly and coAM/poly. 2. If an average-case hard language has an IHIP, then One-Way Functions exist. 3. There is an oracle with respect to which there is a language that has an IHIP but not an SZK proof. 4. IHIP's are closed under composition with any efficiently computable function.
We further study a stronger version of IHIP (that we call Strong IHIP) where the view of the honest prover can be efficiently simulated. For these, we obtain stronger versions of some of the above: 5. Any language with a Strong IHIP is contained in AM and coAM. 6. If a _worst-case_ hard language has a Strong IHIP, then One-Way Functions exist.
Gal Horowitz, Eyal Ronen, Yuval Yarom
We draw on techniques from research into microarchitectural weird gates, software constructs that exploit transient execution to perform arbitrary computation on cache state. We design the Spec-o-Scope gate, a new weird gate that performs 10 cache probes in quick succession, which forms the basis for our eponymous attack. Our Spec-o-Scope attack achieves an order of magnitude improvement in temporal resolution compared to the previous state-of-the-art of Prime+Scope, reducing the measurement time from ~70 cycles to only 5 --- only one cycle more than an L1 cache access. We experimentally verify that our attack can detect timing differences in a 5 cycle resolution. Finally, using our Spec-o-Scope attack, we are able to show the first microarchitectural side-channel attack on an unmodified AES S-box-based implementation, which uses generic CPU features and does not require manipulation of the operating system's scheduler.
Yackolley Amoussou-Guenou, Lionel Beltrando, Maurice Herlihy, Maria Potop-Butucaru
22 May 2024
Max Duparc, Tako Boris Fouotsa
The most intriguing novelty in SQIPrime is the use of non-smooth degree isogenies as challenge isogeny. In fact, in the SQISign family identification scheme, the challenge isogeny is computed by the verifier, who is not well-equipped to compute an isogeny of large non-smooth degree. To overcome this obstacle, the verifier samples the kernel of the challenge isogeny and the task of computing this isogeny is accomplished by the prover. The response is modified in such a way that the verifier can check that his challenge isogeny was correctly computed by the prover, on top of verifying the usual response in the SQISign family.
We describe two variants of SQIPrime: SQIPrime4D which uses dimension 4 isogenies to represent the response isogeny, and SQIPrime2D which solely uses dimension 2 isogenies to represent the response isogeny and hence is more efficient compared to SQIPrime4D and to SQISignHD.
Oriol Farràs, Miquel Guiot
In a weighted threshold access structure, each party is assigned a weight according to its importance, and the authorized subsets are those in which the sum of their weights is at least the threshold value. For these access structures, the share size of the best known secret sharing schemes is either linear on the weights or quasipolynomial on the number of parties, which leads to long shares, in general.
In certain settings, a way to circumvent this efficiency problem is to approximate the access structure by another one that admits more efficient schemes. This work is dedicated to the open problem posed by this strategy: Finding secret sharing schemes with a good tradeoff between the efficiency and the accuracy of the approximation.
We present a method to approximate weighted threshold access structures by others that admit schemes with small shares. This method is based on the techniques for the approximation of the Chow parameters developed by De et al. [Journal of the ACM, 2014]. Our method provides secret sharing schemes with share size $n^{1+o(1)}$, where $n$ is the number of parties, and whose access structure is close to the original one. Namely, in this approximation the condition of being authorized or not is preserved for almost all subsets of parties.
In addition, applying the recent results on computational secret sharing schemes by Applebaum et al. [STOC, 2023] we show that there exist computational secret sharing schemes whose security is based on the RSA assumption and whose share size is polylogarithmic in the number of parties.
Kohei Nakagawa, Hiroshi Onuki
In this paper, we propose a new signature scheme, SQIsign2D-East, which requires only two-dimensional isogeny computations for verification, thus reducing the computational cost of verification. First, we generalized an algorithm called RandIsogImg, which computes a random isogeny of non-smooth degree. Then, by using this generalized RandIsogImg, we construct a new signature scheme SQIsign2D-East.
Andreea B. Alexandru, Julian Loss, Charalampos Papamanthou, Giorgos Tsimos, Benedikt Wagner
Damiano Abram, Lawrence Roy, Mark Simkin
Denis Firsov, Benjamin Livshits
21 May 2024
The Test-of-Time award for Eurocrypt 2009 is awarded to the following paper:
A Unified Framework for the Analysis of Side-Channel Key Recovery Attacks, by François-Xavier Standaert, Tal G. Malkin and Moti Yung.
For introducing a structured approach for evaluation of side-channel attacks and countermeasures and for inspiring further connections between the theory of leakage-resilient cryptography and the practice of defending implementations against side-channels attacks.
For more information, see https://www.iacr.org/testoftime.
Congratulations to the winners!
University of Amsterdam, The Netherlands
Closing date for applications:
Contact: dr. Zhiming Zhao
More information: https://vacatures.uva.nl/UvA/job/Assistant-Professor-in-Security-and-Network-Engineering-%2850-teaching%29/794986702/
University of Birmingham, Birmingham, United Kingdom
The School of Computer Science is looking to strengthen the existing Security and Privacy Research group. The available positions are linked to the chair in Applied Cryptography (held by Elisabeth Oswald): were are thus looking for applicants with a specific interest in applied cryptography in the context of hardware and embedded systems security (e.g. pre-silicon leakage and fault analysis, secure embedded software development, statistical side channel and fault evaluation techniques, machine and deep learning for side channels).
Further information about the duties that come with the role, as well as salary information, and information about the School, are available via the link provided. For further questions please contact Prof. Elisabeth Oswald in the first instance. The closing date for applications is June 16th 2024.Closing date for applications:
Contact: Elisabeth Oswald m.e.oswald@bham.ac.uk
More information: https://edzz.fa.em3.oraclecloud.com/hcmUI/CandidateExperience/en/sites/CX_6001/job/4653/?utm_medium=jobshare
Copper.co
Key Responsibilities of the role
Your experience, skills and knowledge
This role is right for you if:
Essential
Desirable
Closing date for applications:
Contact:
Clara Luna
clara.luna@copper.co
More information: https://www.linkedin.com/jobs/view/3922104775
20 May 2024
Youngjin Bae, Jung Hee Cheon, Jaehyung Kim, Damien Stehlé
In this work, we introduce several CKKS bootstrapping algorithms designed specifically for ciphertexts encoding binary data. Crucially, the new CKKS bootstrapping algorithms enable to bootstrap ciphertexts containing the binary data in the most significant bits. First, this allows to decrease the moduli used in bootstrapping, saving a larger share of the modulus budget for non-bootstrapping operations.
In particular, we obtain full-slot bootstrapping in ring degree $2^{14}$ for the first time. Second, the ciphertext format is compatible with the one used in the DM/CGGI fully homomorphic encryption schemes. Interestingly, we may combine our CKKS bootstrapping algorithms for bits with the fast ring packing technique from Bae et al. [CRYPTO'23]. This leads to a new bootstrapping algorithm for DM/CGGI that outperforms the state-of-the-art approaches when the number of bootstraps to be performed simultaneously is in the low hundreds.
Ziyi Guan, Artur Riazanov, Weiqiang Yuan
Mahmoody, Smith and Wu (ICALP 2020) prove that VDFs satisfying both perfect completeness and adaptive perfect uniqueness do not exist in the random oracle model. Moreover, Ephraim, Freitag, Komargodski, and Pass (EUROCRYPT 2020) construct a VDF with perfect completeness and computational uniqueness, a much weaker guarantee compare to perfect uniqueness, in the random oracle model under the repeated squaring assumption.
In this work, we close the gap between existing constructions and known lower bounds by showing that VDFs with imperfect completeness and non-adaptive computational uniqueness cannot be constructed in the pure random oracle model (without additional computational assumptions).
Ashrujit Ghoshal, Baitian Li, Yaohua Ma, Chenxin Dai, Elaine Shi
Ky Nguyen, David Pointcheval, Robert Schädlich
In this paper, we provide new proof techniques to analyze a new concrete construction of function-hiding DMCFE for inner products, with strong security guarantees in the random oracle model: the adversary can adaptively query multiple challenge ciphertexts and multiple challenge keys, with unbounded repetitions of the same message tags in the ciphertext-queries and a fixed polynomially-large number of repetitions of the same key tags in the key-queries, allowing static corruption of the secret encryption keys. Previous constructions were proven secure in the selective setting only.