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03 July 2023
Logan Allen, Brian Klatt, Philip Quirk, Yaseen Shaikh
We introduce Eden, an Efficient Dyck Encoding of Nock that serves as a practical, SNARK-friendly combinator function and instruction set architecture. We describe arithmetization techniques and polynomial equations used to represent the Eden ISA in an Interactive Oracle Proof. Eden provides the ability to prove statements regarding the execution of any program that compiles down to the Eden ISA. We present the Eden zkVM, a particular instantiation of Eden as a zk-STARK.
Daphné Trama, Pierre-Emmanuel Clet, Aymen Boudguiga, Renaud Sirdey
Victor Shoup
One such notable protocol is FROST, which provides security even with an unlimited number of presignatures; moreover, assuming unused presignatures are available, signing requests can be processed concurrently with minimal latency. Unfortunately, FROST is not a robust protocol, at least in the asynchronous communication model (arguably the most realistic model for such a protocol). Indeed, a single corrupt party can prevent any signatures from being produced. Recently, a protocol called ROAST was developed to remedy this situation. Unfortunately, ROAST is significantly less efficient that FROST (each signing request runs many instances of FROST concurrently).
A more recent protocol is SPRINT, which provides robustness without synchrony assumptions, and actually provides better throughput than FROST. Unfortunately, SPRINT is only secure in very restricted modes of operation. Specifically, to avoid a subexponential attack, only a limited number of presignatures may be produced in advance of signing requests, which somewhat defeats the purpose of presignatures.
Our main new result is to show how to securely combine the techniques used in FROST and SPRINT, allowing one to build a threshold Schnorr signing protocol that (i) is secure and robust without synchrony assumptions (like SPRINT), (ii) provides security even with an unlimited number of presignatures, and (assuming unused presignatures are available) signing requests can be processed concurrently with minimal latency (like FROST), (iii) achieves high throughput (like SPRINT), and (iv) achieves optimal resilience.
Besides achieving this particular technical result, one of our main goals in this paper is to provide a unifying framework in order to better understand the techniques used in various protocols. To that end, we attempt to isolate and abstract the main ideas of each protocol, stripping away superfluous details, so that these ideas can be more readily combined and implemented in different ways. More specifically, to the extent possible, we try to avoid talking about distributed protocols at all, and rather, we examine the security of the ordinary, non-threshold Schnorr scheme in "enhanced" attack modes that correspond to attacks on various types of threshold signing protocols.
Another one of our goals to carry out a security analysis of these enhanced attack modes in the Generic Group Model (GGM), sometimes in conjunction with the Random Oracle Model (ROM). Despite the limitations of these models, we feel that giving security proofs in the GGM or GGM+ROM provides useful insight into the concrete security of the various enhanced attack modes we consider.
Amit Jana, Anup Kumar Kundu, Goutam Paul
Charlotte Hoffmann, Mark Simkin
Benhamouda et al. (CRYPTO'18) proved that Shamir's secret sharing scheme is one bit leakage-resilient for reconstruction threshold $t\geq0.85n$ and conjectured that the same holds for $t=c\cdot n$ for any constant $0\leq c\leq1$. Nielsen and Simkin (EUROCRYPT'20) showed that this is the best one can hope for by proving that Shamir's scheme is not secure against one-bit leakage when $t=c\cdot n/\log(n)$.
In this work, we strengthen the lower bound of Nielsen and Simkin. We consider noisy leakage-resilience, where a random subset of leakages is replaced by uniformly random noise. We prove a lower bound for Shamir's secret sharing, similar to that of Nielsen and Simkin, which holds even when a constant fraction of leakages is replaced by random noise. To this end, we first prove a lower bound on the share size of any noisy-leakage-resilient sharing scheme. We then use this lower bound to show that there exist universal constants $c_1,c_2$, such that for infinitely many $n$, it holds that Shamir's secret sharing scheme is not noisy-leakage-resilient for $t\leq c_1\cdot n/\log(n)$, even when a $c_2$ fraction of leakages are replaced by random noise.
Omid Mir, Balthazar Bauer, Scott Griffy, Anna Lysyanskaya, Daniel Slamanig
Binbin Tu, Xiangling Zhang, Yujie Bai, Yu Chen
In this work, we first formalize a new ideal functionality called shared characteristic and its labeled variety called shared characteristic with labels, from which we propose the frameworks of PCSI/PCLSI protocols. By instantiating our frameworks, we obtain a series of efficient PCSI/PCLSI protocols, whose communication complexity is linear in the size of the small set, and logarithmic in the large set.
We demonstrate the practicality of our protocols with implementations. Experiment results show that our protocols outperform previous ones and the larger difference between the sizes of two sets, the better our protocols perform. For input set sizes $2^{10}$ and $2^{22}$ with items of length $128$ bits, our PCSI requires only $4.62$MB of communication to compute the cardinality; $4.71$MB of communication to compute the cardinality-sum. Compared with the state-of-the-art PCSI proposed by Chen et al., there are $ 58 \times$ and $77 \times$ reductions in the communication cost of computing cardinality and cardinality-sum.
Sahar Mazloom, Benjamin E. Diamond, Antigoni Polychroniadou, Tucker Balch
Anasuya Acharya, Carmit Hazay, Oxana Poburinnaya, Muthuramakrishnan Venkitasubramaniam
Our first main result is a compiler that can transform any $n$-party protocol that is semi-honestly secure with statistical security tolerating an adversary structure $\mathcal{Z}$ to one that (additionally) provides semi-honest fall-back security w.r.t $\mathcal{Z}$. The resulting protocol has optimal round complexity, up to a constant factor, and is optimal in assumptions and the adversary structure. Our second result fully characterizes when malicious fall-back security is feasible. More precisely, we show that malicious fallback secure protocol w.r.t $\mathcal{Z}$ exists if and only if $\mathcal{Z}$ admits unconditional MPC against a semi-honest adversary (namely, iff $\mathcal{Z} \in \mathcal{Q}^2$).
Dan Boneh, Elette Boyle, Henry Corrigan-Gibbs, Niv Gilboa, Yuval Ishai
Beyond the formalization of arithmetic sketching, our contributions are: – A general framework for constructing arithmetic sketching schemes from algebraic varieties. This framework unifies schemes from prior work and gives rise to schemes for useful new languages and with improved soundness error. – The first arithmetic sketching schemes for languages of sparse vectors: vectors with bounded Hamming weight, bounded $L_1$ norm, and vectors whose few non-zero values satisfy a given predicate. – A method for “compiling” any arithmetic sketching scheme for a language $\mathcal{L}$ into a low-communication malicious-secure multi-server protocol for securely testing that a client-provided secret-shared vector is in $\mathcal{L}$.
We also prove the first nontrivial lower bounds showing limits on the sketch size for certain languages (e.g., vectors of Hamming-weight one) and proving the non-existence of arithmetic sketching schemes for others (e.g., the language of all vectors that contain a specific value).
Pedro Branco, Nico Döttling, Akshayaram Srinivasan
At the heart of our construction is a primitive called statistical co-PIR, essentially a a public key encryption scheme which statistically erases bits of the message in a few hidden locations. Our scheme achieves nearly optimal ciphertext size and provides statistical security against malicious receivers. Computational security against semi-honest senders holds under the DDH assumption.
Gauri Gupta, Krithika Ramesh, Anwesh Bhattacharya, Divya Gupta, Rahul Sharma, Nishanth Chandran, Rijurekha Sen
30 June 2023
CEA Grenoble, France
Closing date for applications:
Contact: PhD Nicolas BELLEVILLE, nicolas.belleville@cea.fr
More information: https://www.hipeac.net/jobs/14099/phd-combination-of-software-countermeasures-against-side-channel-attacks/
University of Luxembourg, Esch-sur-Alzette, Luxembourg
The CryptoLux group of the University of Luxembourg has a vacancy for a post-doctoral researcher in the area of security/privacy of blockchains and smart contracts. The successful candidate will contribute to a research project entitled Advanced Cryptography for Finance and Privacy (CryptoFin), which is funded by the Fonds National de la Recherche (FNR). Starting in September 2023, CryptoFin will run over a period of 3 years and be carried out in collaboration with the cryptography teams of Stanford University and Ethereum foundation. The mission of the CryptoFin project is to develop innovative solutions for some of the most pressing research problems in the blockchain domain, especially in the context of layer-2 protocols for off-chain transactions and the design of advanced cryptographic techniques like verifiable delay functions, proof-of-X systems with special features, and new MPC/SNARK-friendly primitives.
Candidates must hold a Ph.D. degree in cryptography, IT security, or a related field. Preference will be given to candidates with a strong publication record that includes at least one paper at an IACR conference/workshop or one of the top-4 security conferences. Experience in blockchains and/or smart contracts is a plus. Candidates with an interest to conduct research in one of the following areas are particularly encouraged to apply:
- Applied cryptography (especially design/analysis of symmetric cryptosystems)
- Cryptofinance and cryptoeconomics
- Privacy and anonymity on the Internet
The position is initially offered for 1 year, but an extension by 2 years is possible. The University of Luxembourg offers excellent working conditions and a highly competitive salary. Interested candidates are invited to send their application by email to Prof. Alex Biryukov before July 20, 2023 (early submission is encouraged). The application material should contain a cover letter explaining the candidate's research interests, a CV (incl. photo), a list of publications, scans of diploma certificates, and contact details of 3 references.
Closing date for applications:
Contact: Prof. Alex Biryukov (alex.biryukov@uni.lu)
More information: https://cryptolux.org/index.php/Vacancies
University of Luxembourg, Esch-sur-Alzette, Luxembourg
The CryptoLux group of the University of Luxembourg has two vacancies for Ph.D. positions in the area of security/privacy of blockchains and smart contracts. The successful candidates will contribute to a research project entitled Advanced Cryptography for Finance and Privacy (CryptoFin), which is funded by the Fonds National de la Recherche (FNR). Starting in September 2023, CryptoFin will run over a period of 3 years and be carried out in collaboration with the cryptography teams of Stanford University and Ethereum foundation. The mission of the CryptoFin project is to develop innovative solutions for some of the most pressing research problems in the blockchain domain, especially in the context of layer-2 protocols for off-chain transactions and the design of advanced cryptographic techniques like verifiable delay functions, proof-of-X systems with special features, and new MPC/SNARK-friendly primitives.
Candidates must hold an M.Sc. degree (or earn an M.Sc. degree before September 2023) in computer science, mathematics, or a related field. Experience in blockchains and/or smart contracts is a plus. Candidates with an interest to conduct research in one of the following areas are particularly encouraged to apply:
- Applied cryptography (especially design/analysis of symmetric cryptosystems)
- Cryptofinance and cryptoeconomics
- Privacy and anonymity on the Internet
Both positions are fully funded and initially offered for 3 years, but an extension to a 4th year is possible. The University of Luxembourg offers excellent working conditions and a highly competitive salary. Interested candidates are invited to send their application by email to Prof. Alex Biryukov before July 20, 2023 (early submission is encouraged). The application material should contain a cover letter explaining the candidate's research interests, a CV (incl. photo), scans of diploma certificates, and contact details of 3 references.
Closing date for applications:
Contact: Prof. Alex Biryukov (alex.biryukov@uni.lu)
More information: https://cryptolux.org/index.php/Vacancies
Technische Universität Darmstadt, Germany
The newly stablished Cyber Security group is one of the core groups forming the faculty of Computer Science in the Technische Universität Darmstadt and National Research Center for Applied Cybersecurity (ATHENE). The research focus of the group is on the security of implementations. A large part of our research is dedicated to hardware security, protection against physical attacks (side-channel analysis and fault-injection attacks), security analysis of real-world systems particularly internet of things, and efficient hardware and software implementation of cryptographic primitives. This includes various implementation platforms like ASICs, FPGAs, and micro-processors.
The group is looking for excellent B.Sc. and M.Sc. graduates with outstanding grades and degrees in computer science, electrical engineering, and mathematics. In addition, we are looking for outstanding postdoctoral candidates from these fields. Initially, we offer three-year fully funded positions for B.Sc. and M.Sc. graduates. The expectation is to work towards a doctorate. Postdoctoral positions are initially offered a 2-year contract. Both PhD and Postdoctoral positions are subject to extensions. The salary will be according to the remuneration group E 13 TV-L (full time).
Our offerings:- Excellent research environment with award-winning scientists,
- Open team culture,
- Programs designed to support parents,
- Support measures for women in IT security,
- Excellent support for doctoral and postdoctoral researchers,
- Opportunities for academic and professional development,
- Budget for courses, conferences, equipment and international exchange
Are you interested? Please send your complete application documents in one single pdf file. The required documents are: Curriculum Vitae, transcript of records of BSc., transcript of records of MSc. (if applicable), two reference names (supervisors or other researchers with whom you worked).
Closing date for applications:
Contact: Amir Moradi (amir.moradi@rub.de)
SandboxAQ; Remote, Europe
We have a postdoc position available at SandboxAQ[1]. We are looking for people broadly interested in post-quantum cryptography. The position is remote in Europe but we have funds to allow travel to meet other team members. The position is initially for one year, but with the option to extend it to up to 3 years, on mutual agreement.
You can learn more about what we’ve been doing so far by checking out our publications page [2] or the individual DBPL pages of our permanent researchers:
- Carlos Aguilar Melchor (PQC Team) https://dblp.uni-trier.de/pid/71/4606.html
- Martin Albrecht (PQC Team) https://dblp.uni-trier.de/pid/92/7397.html
- Nina Bindel (PQC Team) https://dblp.uni-trier.de/pid/167/3021.html
- Nicolas Gama (Privacy Team) https://dblp.uni-trier.de/pid/49/4575.html
- Sandra Guasch (Privacy Team) https://dblp.uni-trier.de/pid/86/8292.html
- James Howe (PQC Team) https://dblp.uni-trier.de/pid/163/8680.html
- David Joseph (PQC Team) https://dblp.uni-trier.de/pid/27/884.html
We are committed to creating an inclusive culture where we have zero tolerance for discrimination. We invest in our employees' personal and professional growth.
To apply, submit an application at https://www.sandboxaq.com/careers-list?gh_jid=4914493004 Please submit your application by 15 July.
[1] https://www.sandboxaq.com/ [2] https://pub.sandboxaq.com/
Closing date for applications:
Contact:
- Martin Albrecht <martin.albrecht@sandboxquantum.com>
- Nina Bindel <nina.bindel@sandboxquantum.com>
More information: https://www.sandboxaq.com/careers-list?gh_jid=4914493004
Chair of IT Security at the Brandenburg University of Technology Cottbus-Senftenberg
Position is limited to 3 years, full time, with possibility for extension.
Tasks:- Active research in the area of intrusion detection systems (IDS) for critical infrastructures, secure cyber-physical systems, and artificial intelligence / machine learning for traffic analysis
- Implementation and evaluation of new algorithms and methods
- Cooperation and knowledge transfer with industrial partners
- Publication of scientific results
- Assistance with teaching
- Master’s degree (or equivalent) and PhD degree (only for PostDocs) in Computer Science or related disciplines
- Strong interest in IT security and/or networking and distributed systems
- Knowledge of at least one programming language (C++, Java, etc.) and one scripting language (Perl, Python, etc.) or strong willingness to quickly learn new programming languages
- Linux/Unix skills
- Knowledge of data mining, machine learning, statistics and result visualization concepts is of advantage
- Excellent working knowledge of English; German is of advantage
- Excellent communication skills
We value diversity and therefore welcome all applications – regardless of gender, nationality, ethnic and social background, religion/belief, disability, age, sexual orientation, and identity. The BTU Cottbus-Senftenberg strives for a balanced gender relation in all employee groups. Applicants with disabilities will be given preferential treatment if they are equally qualified.
Applications containing the following documents:- A detailed Curriculum Vitae
- Transcript of records from your Master studies
- An electronic version of your Master thesis, if possible should be sent in a single PDF file as soon as possible, but not later than 09.07.2023 at itsec-jobs.informatik@lists.b-tu.de.
Closing date for applications:
Contact: For more information about the vacant position please contact Prof. A. Panchenko (E-Mail: itsec-jobs.informatik@lists.b-tu.de)
More information: https://www.b-tu.de/en/fg-it-sicherheit
QuSoft / University of Amsterdam
Are you fascinated by security in theory and/or practice? Are you willing to take on the challenge of securing the next generation of computer systems and networks? Do you like to work in a team of young researchers? Join our dynamic team as a Postdoctoral Researcher and contribute to ground-breaking research at the forefront of quantum technology!
Quantum technologies are advancing at an unprecedented pace. On one hand, the progress in developing quantum computers poses a significant threat to our security infrastructure, particularly concerning public-key cryptography. On the other hand, the integration of quantum communication and quantum data into our networks presents novel opportunities that can enhance security functionalities. However, at present, quantum components predominantly exist in experimental stages, and their security requires in-depth study and assessment.
Among the prominent applications of quantum networks is quantum key distribution (QKD), which theoretically offers superior security guarantees compared to classical cryptographic schemes. However, does the utilization of QKD truly provide tangible benefits over post-quantum cryptography? In the realistic context of trusted-node QKD networks, what kind of security guarantees can be proven depending on the deployed key-management system?
At a broader level, this postdoc position aims to investigate the advantages of exploiting quantum effects within the domain of security and explore the integration of quantum and classical security guarantees both in theory and practice.
The fully funded postdoc position will be within the Theory of Computer Science (TCS) group but will be carried out in close collaboration with researchers at QuSoft. The position is a part of the Quantum Delta NL growth fund project CAT-2, which focuses on the development of a national quantum network, and it will likely involve collaboration with the experimental and theoretical partners of the CAT-2 project.
Closing date for applications:
Contact: Christian Schaffner
More information: https://vacatures.uva.nl/UvA/job/PD/773632702/
29 June 2023
Yongha Son, Jinhyuck Jeong
In this work, we suggest new efficient proposals for circuit-PSI tailored for unbalanced inputs, which feature {\emph{zero}} small set holder side storage, and comparable online phase performance to the previous work. At the technical core, we use homomorphic encryption (HE) based {\emph{plain}} PSI protocols of Cong \textit{et al.} (CCS'21), with several technically non-trivial arguments on algorithm and security.
We demonstrate the superiority of our proposals in several input set sizes by an implementation. As a representative example, for input sets of size $2^{24}$ and $2^{12}$, our proposals require {\emph{zero}} storage on the small set holder whereas Lepoint \textit{et al.} requires over $7$GB. The online phase remains similar; over LAN network setting, ours takes $7.5$ (or $20.9$s) seconds with $45$MB (or $11.7$MB) communication, while Lepoint \textit{et al.} requires $4.2$ seconds with $117$MB communication.