IACR News
Here you can see all recent updates to the IACR webpage. These updates are also available:
25 August 2021
Simin Ghesmati, Walid Fdhila, Edgar Weippl
Walid Fdhila , Nicholas Stifter, Kristian Kostal, Cihan Saglam, Markus Sabadello
Animesh Roy, Dibyendu Roy, Subhamoy Maitra
Jeongeun Park
In this paper, we suggest more efficient evaluation key generation algorithm for the existing variants of MKHE schemes which have no ciphertext expansion for a fixed number of users. Our method only requires a very simple and minor pre-processing; distributing public keys, which is not counted as a round at all in many other applications. As a result, participants have less communication, computation, and memory cost in online phase. Moreover, we provide a practical conversion algorithm between the two types of schemes in order to \emph{efficiently} utilize both schemes' advantages together in more various applications. We also provide detailed comparison among similar results so that users can choose a suitable scheme for their homomorphic encryption based application scenarios.
Yao Sun
Joël Alwen, Sandro Coretti, Yevgeniy Dodis, Yiannis Tselekounis
Dmitrii Koshelev
This short note explains how to hash onto $\mathbb{G}_2$ more efficiently and why we do not need to hash directly onto $\mathbb{G}_1$. In the first case, we significantly exploit the presence of clearing the cofactor $c_2 := N_2/r$. In the second one, on the contrary, clearing the cofactor $c_1 := N_1/r$ can be fully avoided. The fact is that optimal ate pairings $a\!: \mathbb{G}_2 \!\times\! \mathbb{G}_1 \to \mu_r \subset \mathbb{F}_{\!q^k}^*$ can be painlessly (unlike $E_2(\mathbb{F}_{\!q^e}) \!\times\! \mathbb{G}_1$) extended to $\mathbb{G}_2 \!\times\! E_1(\mathbb{F}_{\!q})$, at least in main pairing-based protocols. Throughout the text we mean hashing indifferentiable from a random oracle.
At the moment, the curve BLS12-381 (with $e = 2$) is the most popular in practice. Earlier for this curve (and a number of others) the author constructed encodings $\mathbb{F}_{\!q}^2 \to E_1(\mathbb{F}_{\!q})$ and $\mathbb{F}_{\!q} \to E_2(\mathbb{F}_{\!q^2})$ computable in constant time of one exponentiation in $\mathbb{F}_{\!q}$. Combining the new ideas with these encodings, we obtain hash functions $\{0, 1\}^* \to E_1(\mathbb{F}_{\!q})$ and $\{0, 1\}^* \to \mathbb{G}_2$, which seem to be difficult to speed up even more. We also discuss how much performance gain they provide over hash functions that are actively applied in the industry.
Muhammad Haris Mughees, Hao Chen, Ling Ren
24 August 2021
TalTech, Centre for HW Security; Tallinn, Estonia
Closing date for applications:
Contact: Prof. Samuel Pagliarini
More information: https://taltech.ee/en/centre-for-hardware-security
University of Kassel, Faculty of Electrical Engineering and Computer Science
Closing date for applications:
Contact: Prof. Martin Lange
More information: https://stellen.uni-kassel.de/jobposting/5ac159573541cad232848aa64b14896cd6f190d90?ref=homepage
Graz University of Technology, Graz, Austria
- Formal Methods and Security
- Privacy Technologies
- Systems Security
- Usable Security & Privacy
The professorship will be part of the Institute of Applied Information Processing and Communications, which is an internationally visible research environment with more than 60 researchers in information security. The institute collaborates closely with research groups and industry partners around the globe. It is a central part of the recently established Cybersecurity Campus Graz, which unites basic research, education, technology transfer, and industry partners in cybersecurity all under one roof.
The new professor will build an internationally visible group, and will be an engaged teacher in the Computer Science programs at the Bachelor’s, Master’s, and PhD level. At Graz University of Technology, undergraduate courses are taught in German or English and graduate courses are taught in English.
The full description for this professorship can be found here: https://www.tugraz.at/fakultaeten/csbme/news/jobs-grants-calls/tenure-track-professor-in-security-and-privacy/
Closing date for applications:
Contact: For further questions, please contact Stefan Mangard - stefan.mangard@iaik.tugraz.at
The application should be filed online via https://survey.tugraz.at/index.php/264524 until 30.11.2021 referencing 7050/21/008.
More information: https://www.tugraz.at/fakultaeten/csbme/news/jobs-grants-calls/tenure-track-professor-in-security-and-privacy/
Durham University, UK
The Department of Computer Science at Durham University is looking for a postdoctoral researcher from 1 Jan 2022 to work on an EPSRC project on topics related to password-hashing algorithms and idealized models of computation for a period of two years. We would be interested in applicants holding (or nearing the completion of) a PhD in Cryptography (or related fields) who have strong interests in the foundational aspects of crypto, proof techniques, and definitional work. Publications at competitive venues and ability to work independently are a plus. Applicants with backgrounds in Algorithms and Complexity are also very welcome to apply.
Durham is one of the top (and oldest) universities in the UK, and the CS department hosts one of the strongest Theory groups in the UK across the ACiD and NESTiD groups. The annual salary for the position is £42,149.
Closing date for applications:
Contact: Pooya Farshim. Please submit a CV containing publications and references.
More information: https://farshim.github.io/
23 August 2021
Ege Erdogan, Alptekin Kupcu, A. Ercument Cicek
In this paper, we propose SplitGuard, a method by which a split learning client can detect whether it is being targeted by a training-hijacking attack or not. We experimentally evaluate its effectiveness, and discuss in detail various points related to its use. We conclude that SplitGuard can effectively detect training-hijacking attacks while minimizing the amount of information recovered by the adversaries.
Zhiyuan Fan, Jiatu Li, Tianqi Yang
* In general $B_2$ circuits, assuming the existence of PRFs, PRFs can be constructed in $2n + o(n)$ size, simplifying and improving the $O(n)$ bound by Ishai et al. (STOC 2008). We show that such construction is almost optimal by giving an unconditional $2n-O(1)$ lower bound.
* In logarithmic depth circuits, assuming the existence of $NC^1$ PRFs, PRFs can be constructed in $2n + o(n)$ size and $(1+\epsilon) \log n$ depth simultaneously.
* In constant depth linear threshold circuits, assuming the existence of $TC^0$ PRFs, PRFs can be constructed with wire complexity $n^{1+O(1.61^{-d})}$. We also give an $n^{1+\Omega(c^{-d})}$ wire complexity lower bound for some constant $c$.
The upper bounds are proved with generalized Levin's trick and novel constructions of "almost" universal hash functions; the lower bound for general circuits is proved via a tricky but elementary wire-counting argument; and the lower bound for $TC^0$ circuits is proved by extracting a "black-box" property of $TC^0$ circuits from the "white-box" restriction lemma of Chen, Santhanam, and Srinivasan (Theory Comput. 2018). As a byproduct, we prove unconditional tight upper and lower bounds for "almost" universal hashing, which we believe to have independent interests.
Following Natural Proofs by Razborov and Rudich (J. Comput. Syst. Sci. 1997), our results make progress in realizing the difficulty to improve known circuit lower bounds which recently becomes significant due to the discovery of several "bootstrapping results". In $TC^0$, this reveals the limitation of the current restriction-based methods; in particular, it brings new insights in understanding the strange phenomenon of "sharp threshold results" such as the one presented by Chen and Tell (STOC 2019).