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12 October 2023
Aarhus University (DK)
Deadline:1 November 2023. https://phd.nat.au.dk/for-applicants/open-calls/november-2023/verified-voting-protocols-and-blockchains
The PhD positions include full tuition waiver and a very competitive scholarship. Aarhus University provides international students with a safe and stable environment, a high standard of living and a wealth of social opportunities. Besides having an excellent reputation that enables our PhD graduates to find outstanding employment prospects, Aarhus University offers attractive working conditions, research support and campus resources.
https://cs.au.dk/education/phd/
https://international.au.dk/
This project is supported by the Danish DIREC research center. It is a collaboration between Aarhus University, the Alexandra Institute and Concordium ApS. The aim of the project is work towards secure implementations of Blockchain Voting Governance Protocols and Internet Voting Protocols.
Voting and blockchains are intimately connected. Voting is used in blockchains for consensus, governance, and decentralized organizations. Conversely, elections are based on trust, which means that election systems ideally should be based on algorithms and data structures that are already trusted. Blockchains provide such a technology. They provide a trusted bulletin board, which can be used as part of some voting protocols. Moreover, voting crucially depends on establishing the identity of the voter to avoid fraud and to establish eligibility verifiability. Decades of research in voting protocols have shown how difficult it is to combine the privacy of the vote with the auditability of the election outcome. It is easy to achieve one without the other, but hard to combine both into one protocol. Thus, the topic of this research proposal is to investigate voting protocols and their relation to blockchains. The team will work on security proofs of these protocols and their implementations.
Closing date for applications:
Contact: Bas Spitters
More information: https://phd.nat.au.dk/for-applicants/open-calls/november-2023/verified-voting-protocols-and-blockchains
a16z crypto research, New York, NY, USA
Closing date for applications:
Contact: Joseph Bonneau
More information: https://a16z.com/about/jobs/?gh_jid=5766443003
11 October 2023
Maria Corte-Real Santos, Jonathan Komada Eriksen, Michael Meyer, Krijn Reijnders
Siemen Dhooghe, Artemii Ovchinnikov, Dilara Toprakhisar
Yanbin Xu, Yonglin Hao, Mingxing Wang
Srivatsan Sridhar, Dionysis Zindros, David Tse
Yuncong Zhang, Shi-Feng Sun, Ren Zhang, Dawu Gu
In this work, we focus on random-access memory, an influential and expensive component of ZKVMs. Specifically, we investigate the state-of-the-art protocols for validating the correct functioning of memory, which we refer to as the \emph{memory consistency checks}. Isolating these checks from the rest of the system allows us to formalize their definition and security notion. Furthermore, we summarize the state-of-the-art constructions using the Polynomial IOP model and formally prove their security. Observing that the bottleneck of existing designs lies in sorting the entire memory trace, we break away from this paradigm and propose a novel memory consistency check, dubbed $\mathsf{Permem}$. $\mathsf{Permem}$ bypasses this bottleneck by introducing a technique called the address cycle method, which requires fewer building blocks and---after instantiating the building blocks with state-of-the-art constructions---fewer online polynomial oracles and evaluation queries. In addition, we propose $\mathsf{gcq}$, a new construction for the lookup argument---a key building block of the memory consistency check, which costs fewer online polynomial oracles than the state-of-the-art construction $\mathsf{cq}$.
Miranda Christ, Kevin Choi, Joseph Bonneau
Sourav Das, Ling Ren
In this paper, we present the first adaptively secure threshold BLS signature scheme that relies on the hardness of DDH and co-CDH in asymmetric pairing group in the Random Oracle Model (ROM). Our signature scheme also has non-interactive signing, compatibility with non-threshold BLS verification, and practical efficiency like Boldyreva's scheme. Moreover, to achieve static security, our scheme only needs the hardness of CDH in the ROM, which is the same as the standard non-threshold BLS signature. These properties make our protocol a suitable candidate for practical adoption with the added benefit of provable adaptive security. We also present an efficient distributed key generation (DKG) protocol to set up the signing keys for our signature scheme. We implement our scheme in Go and evaluate its signing and aggregation costs.
Xiuquan Ding, Giulio Malavolta, Tianwei Zhang
In this work, we consider the problem of doubly efficient batched PIR (DEBPIR), where the client wishes to download multiple entries. This problem arises naturally in many practical applications of PIR, or when the database contains large entries. Our main result is a construction of DEBPIR where the amortized communication and server computation overhead is $\tilde{O}(1)$, from the Ring-LWE problem. This represents an exponential improvement compared with known constructions, and it is optimal up to poly-logarithmic factors in the security parameter. Interestingly, the server’s online operations are entirely combinatorial and all algebraic computations are done in the pre-processing or delegated to the client.
Vasily Mikhalev, Nils Kopal, Bernhard Esslinger
Daniel Lammers, Amir Moradi, Nicolai Müller, Aein Rezaei Shahmirzadi
In this paper, we have a deeper look at this technique and provide a comprehensive analysis. The original authors reported that the number of required traces to mount a successful attack increases exponentially with the size of the redundant representation. We however examine their scheme from theoretical point of view. More specifically, we investigate the relationship between RAMBAM and the well-established Boolean masking and, based on this, prove the insecurity of RAMBAM. Through the examples and use cases, we assess the leakage of the scheme in practice and use verification tools to demonstrate that RAMBAM does not necessarily offer adequate protection against SCA attacks neither in theory nor in practice. Confirmed by real-world experiments, we additionally highlight that -- if no dedicated facility is incorporated -- the RAMBAM designs are susceptible to fault-injection attacks despite providing some degree of protection against a sophisticated attack vector, i.e., SIFA.
Xiao Sui, Sisi Duan
Carsten Baum, Nikolas Melissaris, Rahul Rachuri, Peter Scholl
In this work, we present a new, lightweight approach to achieving identifiable abort in dishonest majority MPC. We avoid all of the heavy machinery used in previous works, instead relying on a careful combination of lightweight detection mechanisms and techniques from state-of-the-art protocols secure with (non-identifiable) abort.
At the core of our construction is a homomorphic, multi-receiver commitment scheme secure with identifiable abort. This commitment scheme can be constructed from cheap vector oblivious linear evaluation protocols based on learning parity with noise. To support cheater identification, we design a general compilation technique, similar to a compiler of Ishai et al. (Crypto 2014), but avoid its requirement for adaptive security of the underlying protocol.
Instead, we rely on a different (and seemingly easier to achieve) property we call online extractability, which may be of independent interest. Our MPC protocol can be viewed as a version of the BDOZ MPC scheme (Bendlin et al., Eurocrypt 2011) based on pairwise information-theoretic MACs, enhanced to support cheater identification and a highly efficient preprocessing phase, essentially as efficient as the non-identifiable protocol of Le Mans (Rachuri & Scholl, Crypto 2022).
Alessandro Budroni, Erik Mårtensson
Our contribution consists of giving a polynomial-time approach for calculating the expected complexity of such an enumeration procedure. This allows us to decrease the estimated cost of this procedure and, hence, of the whole attack both classically and quantumly. In addition, we explore different enumeration strategies to achieve some further improvements. Our work is independent from the questions raised by Ducas and Pulles, which do not concern the estimation of the enumeration procedure in the dual attack. As our method of calculating the expected cost of enumeration is fairly general, it might be of independent interest in other areas of cryptanalysis or even in other research areas.
Sudhanshu Sekhar Tripathy, Bichitrananda Behera
10 October 2023
The CFPs are available at the URL: https://iacr.org/jofc/TopicalCollection-mzkp.html
09 October 2023
Olivier Bronchain, Melissa Azouaoui, Mohamed ElGhamrawy, Joost Renes, Tobias Schneider
Jung Hee Cheon, Hyeongmin Choe, Saebyul Jung, Duhyeong Kim, Dah Hoon Lee, Jai Hyun Park
This work focuses on minimizing the number of normalization processes in the PCA algorithm, which is a costly procedure in encrypted PCA. By modifying Krasulina's algorithm, non-polynomial operations were eliminated, except for a single delayed normalization at the end.
Our PCA algorithm demonstrated similar performance to conventional PCA algorithms in face recognition applications. We also implemented it using the CKKS (Cheon-Kim-Kim-Song) homomorphic encryption scheme and obtained the first 6 principal components of a 128$\times$128 real matrix in 7.85 minutes using 8 threads.
Amit Jana, Mostafizar Rahman, Dhiman Saha, Goutam Paul
This work revisits the philosophy of the sandwich attack over multiple rounds for NLFSR-based block ciphers and introduces a new method to find high probability boomerang distinguishers. The approach formalizes boomerang attacks using only ladder, And switches. The cipher is treated as $E = E_m \circ E_1$, a specialized form of a sandwich attack which we called as the ``open-sandwich attack''. The distinguishing probability for this attack configuration is $r \cdot q^2$.
Using this innovative approach, the study successfully identifies a deterministic boomerang distinguisher for the keyed permutation of the TinyJambu cipher over 320 rounds. Additionally, a 640-round boomerang with a probability of $2^{-22}$ is presented with 95% success rate. In the related-key setting, we unveil full-round boomerangs with probabilities of $2^{-19}$, $2^{-18}$, and $2^{-12}$ for all three variants, demonstrating a 99% success rate.
Similarly, for Katan-32, a more effective related-key boomerang spanning 140 rounds with a probability of $2^{-15}$ is uncovered with 70% success rate. Further, in the single-key setting, a 84-round boomerang with probability $2^{-30}$ found with success rate of 60%. This research deepens the understanding of boomerang attacks, enhancing the toolkit for cryptanalysts to develop efficient and impactful attacks on NLFSR-based block ciphers.