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09 September 2020
Olivier Bernard, Adeline Roux-Langlois
Our main contribution is to propose a new ``twisted'' version of the PHS (by Pellet-Mary, Hanrot and Stehlé 2019) algorithm, that we call Twisted-PHS. As a minor contribution, we also propose several improvements of the PHS algorithm. On the theoretical side, we prove that our Twisted-PHS algorithm performs at least as well as the original PHS algorithm. On the practical side though, we provide a full implementation of our algorithm which suggests that much better approximation factors are achieved, and that the given lattice bases are a lot more orthogonal than the ones used in PHS. This is the first time to our knowledge that this type of algorithm is completely implemented and tested for fields of degrees up to~$60$.
Rupeng Yang, Junzuo Lai, Zhengan Huang, Man Ho Au, Qiuliang Xu, Willy Susilo
In this work, we explore the possibility of achieving PKE schemes with receiver selective opening security in the multi-challenge setting. Our contributions are threefold. First, we demonstrate that PKE schemes with RSO security in the single-challenge setting are not necessarily RSO secure in the multi-challenge setting. Then, we show that it is impossible to achieve RSO security for PKE schemes if the number of challenge ciphertexts under each public key is a priori unbounded. In particular, we prove that no PKE scheme can be RSO secure in the k-challenge setting (i.e., the adversary can obtain k challenge ciphertexts for each public key) if its secret key contains less than k bits. On the positive side, we give a concrete construction of PKE scheme with RSO security in the k-challenge setting, where the ratio of the secret key length to k approaches the lower bound 1.
Rongmao Chen, Xinyi Huang, Moti Yung
In this work, we formulate a practical ASA on PKE encryption algorithm which, perhaps surprisingly, turns out to be much more efficient and robust than existing ones, showing that ASAs on PKE schemes are far more effective and dangerous than previously believed. We mainly target PKE of hybrid encryption which is the most prevalent way to employ PKE in the literature and in practice. The main strategy of our ASA is to subvert the underlying key encapsulation mechanism (KEM) so that the session key encapsulated could be efficiently extracted, which, in turn, breaks the data encapsulation mechanism (DEM) enabling us to learn the plaintext itself. Concretely, our non-black-box yet quite general attack enables recovering the plaintext from only two successive ciphertexts and minimally depends on a short state of previous internal randomness. A widely used class of KEMs is shown to be subvertible by our powerful attack.
Our attack relies on a novel identification and formalization of certain properties that yield practical ASAs on KEMs. More broadly, it points at and may shed some light on exploring structural weaknesses of other ``composed cryptographic primitives,'' which may make them susceptible to more dangerous ASAs with effectiveness that surpasses the known logarithmic upper bound (i.e., reviewing composition as an attack enabler).
Jodie Knapp, Elizabeth A. Quaglia
Ming-Xing Luo, Xiaojun Wang
Avijit Dutta
\noindent is secure upto $2^{2n/3}$ adversarial queries. In this paper, we have shown that if we replace two independent permutations of \textsf{2-TEM} (Cogliati et al., CRYPTO 2015) with a single $n$-bit public permutation, then the resultant construction still guarrantees security upto $2^{2n/3}$ adversarial queries. Using the results derived therein, we also show that replacing the permutation $(\pi_4, \pi_3)$ with $(\pi_1, \pi_2)$ in Eqn.~\eqref{eq:abstract} preserves security upto $2^{2n/3}$ adversarial queries.
Pratik Soni, Stefano Tessaro
Berman and Haitner (Journal of Cryptology, '15) gave a one-call construction which, however, is not hardness preserving -- to obtain a secure PRF (against polynomial-time distinguishers), they need to rely on a naPRF secure against superpolynomial-time distinguishers; in contrast, all known hardness-preserving constructions require $\omega(1)$ calls. This leaves open the question of whether a stronger superpolynomial-time assumption is necessary for one-call (or constant-call) approaches. Here, we show that a large class of one-call constructions (which in particular includes the one of Berman and Haitner) cannot be proved to be a secure PRF under a black-box reduction to the (polynomial-time) naPRF security of the underlying function.
Our result complements existing impossibility results (Myers, EUROCRYPT '04; Pietrzak, CRYPTO '05) ruling out natural specific approaches, such as parallel and sequential composition. Furthermore, we show that our techniques extend to rule out a natural class of constructions making parallel but arbitrary number of calls which in particular includes parallel composition and the two-call, cuckoo-hashing based construction of Berman et al.\ (Journal of Cryptology, '19).
Mihai-Zicu Mina, Emil Simion
Yusai Wu, Liqing Yu, Zhenfu Cao, Xiaolei Dong
Liliya Kraleva, Raluca Posteuca, Vincent Rijmen
Julia Kastner, Julian Loss, Michael Rosenberg, Jiayu Xu
Dmitrii Koshelev
Lunar: a Toolbox for More Efficient Universal and Updatable zkSNARKs and Commit-and-Prove Extensions
Matteo Campanelli, Antonio Faonio, Dario Fiore, Anaïs Querol, Hadrián Rodríguez
We achieve a collection of zkSNARKs with different tradeoffs. One of our constructions achieves the smallest proof size and proving time compared to the state of art for proofs for arithmetic circuits. The language supported by this scheme is a variant of R1CS, called R1CS-lite, introduced by this work. Another of our constructions supports directly standard R1CS and improves on previous work achieving the fastest proving time for this type of constraint systems.
We achieve this result via the combination of different contributions: (1) a new algebraically-flavored variant of IOPs that we call $\mathit{Polynomial}$ $\mathit{Holographic}$ $\mathit{IOPs}$ (PHPs), (2) a new compiler that combines our PHPs with $\mathit{commit}$-$\mathit{and}$-$\mathit{prove}$ $\mathit{\ zkSNARKs}$ for committed polynomials, (3) pairing-based realizations of these CP-SNARKs for polynomials, (4) constructions of PHPs for R1CS and R1CS-lite, (5) a variant of the compiler that yields a commit-and-prove universal zkSNARK.
Radhakrishna Bhat, N R Sunitha
08 September 2020
Research Group COSIC at University of Leuven, Belgium
Closing date for applications:
Contact: jobs-cosic@esat.kuleuven.be
More information: https://www.esat.kuleuven.be/cosic/vacancies/
Research Group Cosic at University of Leuven, Belgium
Closing date for applications:
Contact: jobs-cosic@esat.kuleuven.be
More information: https://www.esat.kuleuven.be/cosic/vacancies/
Research Group Cosic at University of Leuven, Belgium
Closing date for applications:
Contact: jobs-cosic@esat.kuleuven.be
More information: https://www.esat.kuleuven.be/cosic/vacancies/
07 September 2020
HashCloak Inc, Toronto Canada
HashCloak Inc is a R&D lab and consultancy focused on privacy, anonymity and scalability for blockchains and cryptocurrencies. Our team is well-known for working on state of the art Ethereum projects such as Ethereum 2.0, Shyft Network and Althea, for pioneering optimistic rollups and bringing forth the first empirical analysis of Ethereum's privacy guarantees and applications.
We are hiring our very first research engineer that will help us bring our internal research projects to the world. As a research engineer at HashCloak, you will have the opportunity to work on anonymous networking, private information retrieval, zero-knowledge proofs and many more exciting areas at the intersection pf cryptography, game theory and finance!
You will be working with a small, young and international team based in different time zones around the world. We are a remote-only company and have a very flexible and relaxed culture.
As our first research engineer, you will have many of the following qualifications:
- Master's degree or above in cryptography, computer science, mathematics or related fields
- 3+ years programming experience in a systems programming language such as C/C++, Go (Preferred), Rust (Preferred).
- Knowledge of one or more of the following: anonymous networking, zero-knowledge proofs, PIR, MPC
- Knowledge of secure software practices
- Experience in deploying production-ready applications
- Implement PoCs and prototypes for our internal research projects
- Conducting research in one of the previously mentioned fields
- Collaborate with our clients and research partners
- Write papers targeted at top conferences as well as blog posts targeted at general audiences
- Contribute to open source projects that we use in our research
- Stay up to date on research and development in the blockchain and cryptography ecosystems
Closing date for applications:
Contact: Mikerah Quintyne-Collins - CEO and Founder
06 September 2020
Singapore University of Technology and Design (SUTD), Singapore
Interested candidates please send your CV with a research statement to Prof. Jianying Zhou. Only short-listed candidates will be contacted for interview.
Closing date for applications:
Contact: Prof. Jianying Zhou (jianying_zhou@sutd.edu.sg)
More information: http://jianying.space/
Cryptanalysis Taskforce @ Nanyang Technological University, Singapore
- tool aided cryptanalysis, such as MILP, CP, STP, and SAT
- machine learning aided cryptanalysis and designs
- privacy-preserving friendly symmetric-key designs
- quantum cryptanalysis
- theory and Proof
- cryptanalysis against SHA-3 and AES
Closing date for applications:
Contact: Asst Prof. Jian Guo, guojian@ntu.edu.sg
More information: http://team.crypto.sg