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01 December 2023
Daniel R. L. Brown, Chris Monico
Hamza Abusalah, Valerio Cini
Apurva K Vangujar, Alia Umrani, Paolo Palmieri
Ritam Bhaumik, Mohammad Amin Raeisi
Hosein Hadipour, Yosuke Todo
This paper delves into the cryptanalysis of QARMAv2 to enhance our understanding of its security. Given that the integral distinguishers of QARMAv2 are the longest concrete distinguishers for this cipher so far, we focus on integral attack. To this end, we first further improve the automatic tool introduced by Hadipour et al., for finding integral distinguishers of TBCs following the TWEAKEY framework. This new tool exploits the MixColumns property of QARMAv2 to find integral distinguishers more suitable for key recovery attacks. Then, we combine several techniques for integral key recovery attacks, e.g., Meet-in-the-middle and partial-sum techniques to build a fine-grained integral key recovery attack on QARMAv2. Notably, we demonstrate how to leverage the low data complexity of the integral distinguishers of QARMAv2 to reduce the memory complexity of the meet-in-the-middle technique. As a result, we managed to propose the first concrete key recovery attacks on reduced-round versions of QARMAv2 by attacking 13 rounds of QARMAv2-64-128 with a single tweak block, 14 rounds of QARMAv2-64-128 with two independent tweak blocks, and 16 rounds of QARMAv2-128-256 with two independent tweak blocks. Our attacks do not compromise the claimed security of QARMAv2, but they shed more light on the cryptanalysis of this cipher.
Noam Mazor, Rafael Pass
In this note, we present resolutions to some of these questions with respect to the \emph{black-box} analog of these problems. In more detail, let $MK^t_MP[s]$ denote the language consisting of strings $x$ with $K_{M}^t(x) < s(|x|)$, where $K_M^t(x)$ denotes the $t$-bounded Kolmogorov complexity of $x$ with $M$ as the underlying (Universal) Turing machine, and let $search-MK^t_MP[s]$ denote the search version of the same problem.
We show that if there for every Universal Turing machine $U$ there exists a $2^{\alpha n}poly(n)$-size $U$-oracle aided circuit deciding $MK^t_UP [n-O(1)]$, then for every function $s$, and every not necessarily universal Turing machine $M$, there exists a $2^{\alpha s(n)}poly(n)$ size $M$-oracle aided circuit solving $search-MK^t_MP[s(n)]$; this in turn yields circuits of roughly the same size for both the Minimum Circuit Size Problem (MCSP), and the function inversion problem, as they can be thought of as instantiating $MK^t_MP$ with particular choices of (a non universal) TMs $M$ (the circuit emulator for the case of MCSP, and the function evaluation in the case of function inversion).
As a corollary of independent interest, we get that the complexity of black-box function inversion is (roughly) the same as the complexity of black-box deciding $MK^t_UP[n-O(1)]$ for any universal TM $U$; that is, also in the worst-case regime, black-box function inversion is ``equivalent" to black-box deciding $MKtUP$.
François Delobel, Patrick Derbez, Arthur Gontier, Loïc Rouquette, Christine Solnon
Ertem Nusret Tas, Dan Boneh
Yevgeniy Dodis, Daniel Jost, Balachandar Kesavan, Antonio Marcedone
We observe that the vast security literature analyzing asynchronous messaging does not translate well to synchronous video calls. Namely, while strong forms of forward secrecy and post compromise security are less important for (typically short-lived) video calls, various liveness properties become crucial. For example, mandating that participants quickly learn of updates to the meeting roster and key, media streams being displayed are recent, and banned participants promptly lose any access to the meeting. Our main results are as follows:
1. Propose a new notion of leader-based continuous group key agreement with liveness, which accurately captures the E2EE properties specific to the synchronous communication scenario. 2. Prove security of the core of Zoom's E2EE meetings protocol in the above well-defined model. 3. Propose ways to strengthen Zoom's liveness properties by simple modifications to the original protocol, which subsequently influenced updates implemented in production.
Yi Wang, Rongmao Chen, Xinyi Huang, Moti Yung
Here, we reformulate the sender-AME, present the notion of $\ell$-sender-AME and formalize the properties of (strong) security and robustness. Robustness refers to guaranteed delivery of duplicate messages to the intended receiver, ensuring that decrypting normal ciphertexts in an anamorphic way or decrypting anamorphic ciphertexts with an incorrect duplicate secret key results in an explicit abort signal. We first present a simple construction for pseudo-random and robust public key encryption that shares the similar idea of public-key stegosystem by von Ahn and Hopper (EUROCRYPT 2004). Then, inspired by Chen et al.'s malicious algorithm-substitution attack (ASA) on key encapsulation mechanisms (KEM) (ASIACRYPT 2020), we give a generic construction for hybrid PKE with special KEM that encompasses well-known schemes, including ElGamal and Cramer-Shoup cryptosystems.
The constructions of $\ell$-sender-AME motivate us to explore the relations between AME, ASA on PKE, and public-key stegosystem. The results show that a strongly secure $\ell$-sender-AME is such a strong primitive that implies reformulated receiver-AME, public-key stegosystem, and generalized ASA on PKE. By expanding the scope of sender-anamorphic encryption and establishing its robustness, as well as exploring the connections among existing notions, we advance secure communication protocols under challenging conditions.
29 November 2023
Zurich, Switzerland, 25 May - 26 May 2024
Submission deadline: 16 February 2024
Notification: 30 March 2024
Microsoft Research, Redmond, WA
We are looking for creative thinkers, doers, and problem solvers, who are unafraid to venture outside their comfort zone to find solutions to difficult and messy real-world problems. If you are unsure whether you have appropriate background and match this description, we highly recommend applying anyway!
Apply now at: https://jobs.careers.microsoft.com/global/en/job/1639824
Closing date for applications:
Contact: Kim Laine (kim.laine@microsoft.com)
University of St.Gallen, Switzerland
Our research interests are centered around information security and applied cryptography, with the larger goal of safeguarding communications and providing strong privacy guarantees. We are active in several areas, a subset of which include:
- Verifiable computation
- Secure, private and distributed aggregation
- Secure multi-party computation
- Privacy-preserving biometric authentication
- Anonymous credentials
- Distributed and privacy-preserving authentication
The starting date for the position is flexible and come with a very competitive salary. The selection process runs until the suitable candidate has been found. The University of St.Gallen conducts excellent research with international implications. The city of St.Gallen is located one hour from Zurich and offers a high quality of life.
Please apply by 10th December 2023 through the job portal (via link).
Closing date for applications:
Contact:
Please apply through the job portal (via link).
Eriane Breu (Administrative matters)
Prof. Katerina Mitrokotsa (Research related questions)
More information: https://jobs.unisg.ch/offene-stellen/postdoc-fellow-in-cryptography-information-security-m-f-d-m-w-d/831c6e8a-e191-48ec-92d5-320b2822a9ab
ENS Lyon, France
The candidate will be joining the Number Theory team of ENS de Lyon. They will benefit from the resources of AGATHA CRYPTY (travelling, equipment, organizing events, hiring interns...).
The candidate should hold a PhD degree in Mathematics or Computer Science. They should have a strong record related to any of the following research topics: number theory, computational number theory, lattice-based cryptography, isogeny-based cryptography.
Closing date for applications:
Contact: Benjamin Wesolowski. Candidates should apply at: https://emploi.cnrs.fr/Offres/CDD/UMR5669-BENWES-002/Default.aspx?lang=EN
More information: https://emploi.cnrs.fr/Offres/CDD/UMR5669-BENWES-002/Default.aspx?lang=EN
ÉPITA, Paris, France
Teaching. The expected profile is a teacher-researcher capable of teaching the fundamentals of Computer Science (in the core curriculum of an engineering cycle in computer science), as well as specialized subjects close to his/her research themes (in the engineering cycle majors, in apprenticeship training, in the school's international Master's degree and/or Bachelor's degree in cybersecurity). The teaching load is approximately that of a university lecturer.
Research. We are recruiting to consolidate our teams and research areas in the following areas:
- Software and architecture security:
- Detection of security attacks (learning);
- Malware and reverse engineering;
- Cryptography;
- Systems:
- Operating systems and kernels;
- Cloud computing and virtualization;
- Embedded system.
The teacher-researcher's profile will fit into one of these three fields: mathematical computer science, fundamental computer science or applied computer science, a geeky and versatile profile being very welcome.
The "research" component is expected to account for around 45% of time, including participation in national and international research activities (review of articles, etc.). Research will be carried out within a local team and with external collaborators as appropriate. A dynamic approach to setting up and participating in collaborative projects and/or industrial contracts will be highly appreciated
Closing date for applications:
Contact: thierry.geraud@epita.fr
More information: https://www.lre.epita.fr/
Bosch Research, Renningen, Germany
Thus, we are looking for a highly motivated PhD candidate with a strong background and/or interest in applied cryptography. The successful candidate will:
- become a part of the team and advance research on MPC
- develop novel approaches to improve the practical efficiency of actively secure MPC protocols
- design efficient MPC protocols for diverse use-cases
- integrate the results into our Cabyne Stack open source MPC platform
- publish and present the results in top-tier journals and at conferences
- Education: Hold an M.Sc. degree (or equivalent) with excellent grades in IT security, computer science, mathematics, or a related field
- Experience and Knowledge: Strong background in (applied) cryptography with a particular focus on cryptographic protocols/MPC, including security models and basic security proof techniques. Good software development/programming skills and the motivation to integrate scientific results into Carbyne Stack.
- Personality and Working Practice: Self-motivated and enthusiastic, independent, reliable, creative, and able to work in an international team with diverse background
- Language: Fluent English language skills
Closing date for applications:
Contact: Informal inquiries can be made to Christoph Bösch (christoph.boesch (at) de.bosch.com). Formal applications must be submitted through: https://smrtr.io/hmG3C
University of St.Gallen, Switzerland
The student is expected to work on topics that include security and privacy issues in authentication. More precisely, the student will be working on investigating efficient and privacy-preserving authentication that provides: i) provable security guarantees, and ii) rigorous privacy guarantees.
Key Responsibilities:
- Perform exciting and challenging research in the domain of information security and cryptography.
- Support and assist in teaching computer security and cryptography courses.
- The PhD student is expected to have a MSc degree or equivalent, and strong background in cryptography, network security and mathematics.
- Experience in one or more domains such as cryptography, design of protocols, secure multi-party computation and differential privacy is beneficial.
- Excellent programming skills.
- Excellent written and verbal communication skills in English
The starting date for the position is flexible and come with a very competitive salary. The selection process runs until the suitable candidate has been found.
Please apply by 10th December 2023 through the job portal (via link).
Closing date for applications:
Contact:
Please apply through the job portal (via link).
Eriane Breu (Administrative matters)
Prof. Katerina Mitrokotsa (Research related questions)
28 November 2023
Suvradip Chakraborty, Lorenzo Magliocco, Bernardo Magri, Daniele Venturi
We achieve this result by sanitizing the PAKE protocol from oblivious transfer (OT) due to Canetti et al. (PKC'12) via cryptographic reverse firewalls in the UC framework (Chakraborty et al., EUROCRYPT'22). This requires new techniques, which help us uncover new cryptographic primitives with sanitation-friendly properties along the way (such as OT, dual-mode cryptosystems, and signature schemes).
As an additional contribution, we delve deeper in the backbone of communication required in the subversion-resilient UC framework, extending it to the unauthenticated setting, in line with the work of Barak et al. (CRYPTO'05).