IACR News
Here you can see all recent updates to the IACR webpage. These updates are also available:
18 April 2023
Ahmet Ramazan Ağırtaş, Oğuz Yayla
Junrui Liu, Ian Kretz, Hanzhi Liu, Bryan Tan, Jonathan Wang, Yi Sun, Luke Pearson, Anders Miltner, Işıl Dillig, Yu Feng
17 April 2023
Technische Universität Darmstadt
Doctoral Researcher (Research Assistant/PhD Student) in Cryptography and Complexity Theory
in the group of Professor Marc Fischlin. More information about our research is available under www.cryptoplexity.de. The starting date is as soon as possible. The initial funding for the position is for three years, but the contract should be renewable. Candidates are expected to perform scientific research in the areas of the projects, and to contribute to the teaching, research, and administrative tasks of the group.
Your Profile:
• Master’s degree (or equivalent) in Computer Science, Mathematics, or a similar discipline,
• Extensive knowledge in the areas of cryptography and IT security,
• fluent English language skills,
• experience in IT system administration is welcome.
How to Apply
• curriculum vitae, including references,
• copies of relevant diplomas and certificates,
• research statement.
TU Darmstadt is an autonomous university with broad research excellence, interdisciplinary profile and clear emphases in engineering and information and communication technology. The Department of Computer Science is one of the leading CS departments in Europe and placed regularly in the top group in nationwide rankings. In the area of Cybersecurity, TU Darmstadt is one of the leading research institutions within Europe focusing on a broad spectrum of applied and theoretical research. The services rendered as part of the positions function as the scientific qualification of the candidate. The candidates will be given the opportunity to accomplish a doctoral degree.
The application data should be bundled into a single PDF file.
Closing date for applications:
Contact: Prof. Dr. Marc Fischlin, jobs@cx.tu-darmstadt.de
More information: https://www.cryptoplexity.informatik.tu-darmstadt.de/cryptoplexity/jobs_3/index.en.jsp
Agentur für Innovation in der Cybersicherheit "Innovation for Cybersecurity"
Closing date for applications:
Contact: Matthias Strauß, Head of HR, bewerbung@cyberagentur.de
More information: https://app.connectoor.de/jobview?jobid=62d506deddb233fc338b4579
Monash University, Melbourne, Australia
- Post-quantum cryptography (based on lattices and/or hash) and its applications e.g. to blockchain
- Zero-knowledge proofs and their applications e.g. to blockchain
- Blockchain protocols more broadly
- highly competitive tuition fee and stipend scholarships
- opportunities to collaborate with leading academic and industry experts in the related areas
- opportunities to participate in international grant-funded projects
- collaborative and friendly research environment
- an opportunity to live/study in one of the most liveable and safest cities in the world
Requirements. A strong mathematical background is required, but a strong cryptography background is not necessarily a must (but it’s of course a plus). Some knowledge/experience in coding (for example, Python, C/C++, SageMath) is also a plus. Candidates must have completed (or be about to complete within the next 6 months) a significant research component either as part of their undergraduate (honours) degree or masters degree. They should have excellent English verbal and written communication skills.
How to apply. please first refer to https://mfesgin.github.io/supervision/ for more information. Then, please email your CV and bachelor/master transcripts with the subject line "Prospective PhD Student - Your Name"
Closing date for applications:
Contact: Muhammed Esgin (firstname.lastname@monash.edu)
More information: https://mfesgin.github.io/supervision/
Arquimea Research Center ( ARQUIMEA)
Closing date for applications:
Contact: ARQUIMEA web page
More information: https://arquimea.bamboohr.com/careers/240
Brice Colombier, Vincent Grosso, Pierre-Louis Cayrel, Vlad-Florin Drăgoi
Jung Hee Cheon, Wonhee Cho, Jiseung Kim
The compiler is constructed in a modular fashion and includes a compact threshold fully homomorphic encryption, a non-interactive zero-knowledge proof with preprocessing, and a non-interactive commitment. An instantiation of the Universal Thresholdizer can be achieved through the construction of a compact threshold fully homomorphic encryption. Currently, there are two threshold fully homomorphic encryptions based on linear secret sharing, with one using Shamir's secret sharing and the other using the $\{0,1\}$-linear secret sharing scheme ($\{0,1\}$-LSSS). The former fails to achieve compactness as the size of its ciphertext is $O(N\log N)$, where $N$ is the number of participants in the distributed system. Meanwhile, the latter provides compactness, with a ciphertext size of $O(\log N)$, but requires $O(N^{4.3})$ share keys on each party, leading to high communication costs.
In this paper, we propose a communication-efficient Universal Thresholdizer by revisiting the threshold fully homomorphic encryption. Our scheme reduces the number of share keys required on each party to $O(N^{2+o(1)})$ while preserving the ciphertext size of $O(\log N)$. To achieve this, we introduce a new linear secret sharing scheme called TreeSSS, which requires a smaller number of shared keys and satisfies compactness. As a result, the Threshold Fully Homomorphic Encryption underlying our linear secret sharing scheme has fewer shared keys during the setup algorithm and reduced communication costs during the partial decryption algorithm. Moreover, the construction of a Universal Thresholdizer can be achieved through the use of TreeSSS, as it reduces the number of shared keys compared to previous constructions. Additionally, TreeSSS may be of independent interest, as it improves the efficiency in terms of communication costs when used to replace $\{0,1\}$-LSSS.
Jakub Klemsa, Melek Önen
Amit Behera, Zvika Brakerski, Or Sattath, Omri Shmueli
We show that, similarly to PRS, PRSPD can be constructed from any post-quantum one-way function. As far as the authors are aware, this is the first construction of a family of states that satisfies both pseudorandomness and provability of destruction. We show that many cryptographic applications that were shown based on PRS variants using quantum communication can be based on (variants of) PRSPD using only classical communication. This includes symmetric encryption, message authentication, one-time signatures, commitments, and classically verifiable private quantum coins.
Roberto La Scala, Federico Pintore, Sharwan K. Tiwari, Andrea Visconti
Having in mind cryptanalytic applications, we present an implementation of this strategy in an algorithm called MultiSolve which is designed for polynomial systems having at most one solution. We prove explicit formulas for its complexity which are based on probability distributions that can be easily estimated by performing the proposed preprocessing on a testset of evaluations for different subsets of variables. We prove that an optimal complexity of MultiSolve is achieved by using a full multistep strategy with a maximum number of steps and in turn the classical guess-and-determine strategy, which essentially is a strategy consisting of a single step, is the worst choice. Finally, we extensively study the behaviour of MultiSolve when performing an algebraic attack on the well-known stream cipher Trivium.
Han-Ting Chen, Yi-Hua Chung, Vincent Hwang, Chi-Ting Liu, Bo-Yin Yang
Arianna Gringiani, Alessio Meneghetti, Edoardo Signorini, Ruggero Susella
Alexander May, Carl Richard Theodor Schneider
In this work, we explicitly construct smooth auxiliary curves for a dozen of mostly used, standardized elliptic curves of bit-sizes in the range $[204,256]$, including e.g., NIST P-256, Curve25519, SM2 and GOST R34.10. For all these curves we construct a corresponding cyclic auxiliary curve $\hat E(\mathbb{F}_q)$, whose order is $39$-bit smooth, i.e., its largest factor is of bit-length at most $39$ bits.
This in turn allows us to compute for all divisors of the order of $\hat E(\mathbb{F}_q)$ exhaustively a codebook for all discrete logarithms. As a consequence, dlogs on $\hat E(\mathbb{F}_q)$ can efficiently be computed in a matter of seconds. Our resulting codebook sizes are less than 29 TByte, and fit on our hard disk.
We also construct auxiliary curves for NIST P-384 and NIST P-521 with a $65$-bit and $110$-bit smooth order.
Further, we provide an efficient implementation of Maurer's reduction from the dlog computation in $G$ with order $q$ to the dlog computation on its auxiliary curve $\hat E(\mathbb{F}_q)$. Let us provide a flavor of our results, e.g., when $G$ is the NIST P-256 group, the results for other curves are similar. With the help of our codebook for the auxiliary curve $\hat E(\mathbb{F}_q)$, and less than 24,000 calls to a DH oracle in $G$ (that we simulate), we can solve discrete logarithms on NIST P-256 in around 30 secs.
From a security perspective, our results show that for current elliptic curve standards the difficulty of solving DH is practically tightly related to the difficulty of computing dlogs. Namely, unless dlogs are easy to compute on these curves $G$, we provide a very concrete security guarantee that DH in $G$ must also be hard.
From a cryptanalytic perspective, our results show a way to efficiently solve discrete logarithms in the presence of a DH oracle. Thus, if practical implementations unintentionally provide a DH oracle, dlog computations actually become surprisingly easy.
Fuyuki Kitagawa, Ryo Nishimaki, Takashi Yamakawa
Tomer Ashur, Thomas Buschman, Mohammad Mahzoun
14 April 2023
The Test-of-Time award for Eurocrypt 2008 is awarded to the following two papers:
Efficient Non-interactive Proof Systems for Bilinear Groups, by Jens Groth and Amit Sahai, for providing efficient Groth-Sahai proofs that have given rise to many applications including succinct non-interactive arguments.
On the Indifferentiability of the Sponge Construction, by Guido Bertoni, Joan Daemen, Michael Peeters and Gilles Van Assche, for introducing the Sponge construction that is deployed in world-wide standards such as SHA-3 and ASCON.
For more information, see https://www.iacr.org/testoftime.
Congratulations to all winners!
13 April 2023
Victor Shoup, Nigel P. Smart
Sohyun Jeon, Hyang-Sook Lee, Jeongeun Park
In this work, we introduce a new practical subgaussian gadget decomposition algorithm which has the least overhead (less than 14\%) among existing works for certain parameter sets, by combining two previous works. In other words, we bring an existing technique based on an uniform distribution to a simpler and faster design (PKC' 22) to exploit parallel computation, which allows to skip expensive parts due to pre-computation, resulting in even simpler and faster algorithm. When the modulus is large (over 100-bit), our algorithm is not always faster than the other similar work. Therefore, we give a detailed comparison, even for large modulus, with all the competitive algorithms for applications to choose the best algorithm for their choice of parameters.
Zeyu Liu, Eran Tromer, Yunhao Wang
We consider the case of group messaging, where each message may have multiple recipients (e.g., in a group chat or blockchain transaction). A direct use of prior OMR protocols in the group setting increases the servers' work linearly in the group size, rendering it prohibitively costly for large groups.
We thus devise new protocols where the servers' cost grows very slowly with the group size, while recipients' cost is low and independent of the group size. Our approach uses Fully Homomorphic Encryption and other lattice-based techniques, building on and improving on prior work. The efficient handling of groups is attained by encoding multiple recipient-specific clues into a single polynomial or multilinear function that can be efficiently evaluated under FHE, and via preprocessing and amortization techniques.
We formally study several variants of Group Oblivious Message Retrieval (GOMR), and describe corresponding GOMR protocols.
Our implementation and benchmarks show, for parameters of interest, cost reductions of orders of magnitude compared to prior schemes. For example, the servers' cost is $3.36 per million messages scanned, where each message may address up to 15 recipients.