International Association
for Cryptologic Research

In this tutorial, we provide a brief overview of Concurrent Zero Knowledge and next present a simple proof of the existence of Concurrent Zero-knowledge arguments for N P based on one-way permutations.

In recent years, leakage-resilient cryptography---the design of cryptographic protocols resilient to bounded leakage of honest players' secrets---has received significant attention. A major limitation of known provably-secure constructions (based on polynomial hardness assumptions) is that they require the secrets to have sufficient actual (i.e., information-theoretic), as opposed to computational, min-entropy even after the leakage.

In this work, we present barriers to provably-secure constructions beyond the ``information-theoretic barrier'': Assume the existence of collision-resistant hash functions. Then, no NP search problem with $(2^{n^{\epsilon}})$-bounded number of witnesses can be proven (even worst-case) hard in the presence of $O(n^{\epsilon})$ bits of computationally-efficient leakage of the witness, using a black-box reduction to any $O(1)$-round assumption. In particular, this implies that $O(n^{\epsilon})$-leakage resilient injective one-way functions, and more generally, one-way functions with at most $2^{n^{\epsilon}}$ pre-images, cannot be based on any ``standard'' complexity assumption using a black-box reduction.

Attribute-based conditional proxy re-encryption (AB-CPRE) allows delegators to carry out attribute-based control on the delegation of decryption by setting policies and attribute vectors. The fine-grained control of AB-CPRE makes it suitable for a variety of applications, such as cloud storage and distributed file systems. However, all existing AB-CPRE schemes are constructed under classical number-theoretic assumptions, which are vulnerable to quantum cryptoanalysis. Therefore, we propose the first AB-CPRE scheme based on the learning with errors (LWE) assumption. Constructed from fully key-homomorphic encryption (FKHE) and key-switching techniques, our scheme is unidirectional, single-hop, and enables a polynomial-deep boolean circuit as its policy. Furthermore, we split the ciphertext into two independent parts to avoid two-level or multi-level encryption/decryption mechanisms. Taking advantage of it, we then extend our single-hop AB-CPRE into an efficient and concise multi-hop one. No matter how many transformations are performed, the re-encrypted ciphertext is in constant size, and only one encryption/decryption algorithm is needed. Both of our schemes are proved to be selective secure against chosen-plaintext attacks (CPA) in the standard model.

Clustering is an unsupervised machine learning technique that outputs clusters containing similar data items. In this work, we investigate privacy-preserving density-based clustering which is, for example, used in financial analytics and medical diagnosis. When (multiple) data owners collaborate or outsource the computation, privacy concerns arise. To address this problem, we design, implement, and evaluate the first practical and fully private density-based clustering scheme based on secure two-party computation. Our protocol privately executes the DBSCAN algorithm without disclosing any information (including the number and size of clusters). It can be used for private clustering between two parties as well as for private outsourcing of an arbitrary number of data owners to two non-colluding servers. Our implementation of the DBSCAN algorithm privately clusters data sets with 400 elements in 7 minutes on commodity hardware. Thereby, it flexibly determines the number of required clusters and is insensitive to outliers, while being only factor 19x slower than today's fastest private K-means protocol (Mohassel et al., PETS'20) which can only be used for specific data sets. We then show how to transfer our newly designed protocol to related clustering algorithms by introducing a private approximation of the TRACLUS algorithm for trajectory clustering which has interesting real-world applications like financial time series forecasts and the investigation of the spread of a disease like COVID-19.

It is a well-known fact that the power consumption during certain stages of a cryptographic algorithm exhibits a strong correlation with the Hamming Weight of its underlying variables. This phenomenon has been widely exploited in the cryptographic literature in various attacks targeting a broad range of schemes such as block ciphers or public-key cryptosystems. A common way of breaking this correlation is through the inclusion of countermeasures involving additional randomness into the computation in the form of hidden (undisclosed) component functions or masking strategies that complicate the inference of any sensitive information from the gathered power traces. In this work, we revisit the tight correlation between the Hamming Weight and the observed power consumption of an algorithm and demonstrate, in the first part, a practical reverse-engineering attack of proprietary AES-like constructions with secret internal components like the SubBytes, MixColumns and ShiftRows functions. This approach is used in some commercial products such as the Dynamic Encryption package from the communication services provider Dencrypt as an extra layer of security. We recover the encryption key alongside the hidden substitution and permutation layer as well as the MixColumns matrix on both 8-bit and 32-bit architectures.

In a second effort, we shift our attention to a masked implementation of AES, specifically the secAES proposal put forward by the French National Cybersecurity Agency (ANSSI) that concisely combines several side-channel countermeasure techniques. We show its insecurity in a novel side-channel-assisted statistical key-recovery attack that only necessitates a few hundreds of collected power traces.

A new ``Weighted Bit-flipping'' (WBF) iterative decoder is presented and analyzed with respect to its Decoding Failure Rate (DFR). We show that the DFR is indeed lower than that of the BGF decoder as suggested by the BIKE third round submission to the NIST PQC standardization process. The WBF decoder requires more iterations to complete than BGF, but by creating a hybrid decoder we show that a lower DFR compared to that of the BGF decoder can still be achieved while keeping the computational tradeoff to a minimum.

As new and emerging markets, crypto(-currency/-token) markets are susceptible to manipulation and illiquidity. The theory of market economics, offers market makers that bear the promise of bootstrapping/stabilizing such markets and boosting their liquidity. In order, however, to achieve these goals, the market maker operator (typically an exchange) is assumed trusted against manipulations. Common attempts to remove/weaken this trust assumption require several on-chain rounds per trade or use expensive MPC machinery, and/or are susceptible to manipulative market-maker operators that perform informed front-running attacks—i.e., manipulate the sequence of trades using future trade information. Our work proposes a market-maker-based exchange which is resilient against a wide class of front-running (in particular, reordering attacks). When instantiated with a monopolistic profit seeking market maker our system yields a market where the trading price of crypto-tokens converges to a bid-ask spread centered around their true valuation. Importantly, after an initial setup of appropriate smart contracts, the trades are done in an off-chain fashion and smart contracts are invoked asynchronously to the trades. Our methodology yields a highly efficient exchange, where the market maker’s compliance is ensured by a combination of a rational market analysis, cryptographic mechanisms, and smart-contract-based collaterals. We have implemented our exchange in Ethereum and showcase its competitive throughput, its performance under attack, and the associate gas costs.

Layering diverse cryptography is a general method to lower the risk of a future, or secret, cryptanalytic attack on a system. This report describes methods to quantifiably estimate this risk reduction.

Diversity is especially helpful in forward security because future attackers have more time to discover new attacks, making attack independence of diverse cryptography the major contribution to risk reduction. Post-quantum security is a part of forward security.

Estimates for highly sensitive data say that the security advantage of diverse layering is worth the extra usage cost, thus advising a decision to layer diverse cryptography.

We propose the first tight security proof for the ordinary two-message signed Diffie-Hellman key exchange protocol in the random oracle model. Our proof is based on the strong computational Diffie-Hellman assumption and the multi-user security of a digital signature scheme. With our security proof, the signed DH protocol can be deployed with optimal parameters, independent of the number of users or sessions, without the need to compensate any security loss. We abstract our approach with a new notion called verifiable key exchange. In contrast to a known tight three-message variant of the signed Diffie-Hellman protocol (Gjøsteen and Jager, CRYPTO 2018), we do not require any modification to the original protocol, and our tightness result is proven in the “Single-Bit- Guess” model which we know can be tightly composed with symmetric cryptographic primitives to establish a secure channel.

Zero-Knowledge PCPs (ZK-PCPs; Kilian, Petrank, and Tardos, STOC `97) are PCPs with the additional zero-knowledge guarantee that the view of any (possibly malicious) verifier making a bounded number of queries to the proof can be efficiently simulated up to a small statistical distance. Similarly, ZK-PCPs of Proximity (ZK-PCPPs; Ishai and Weiss, TCC `14) are PCPPs in which the view of an adversarial verifier can be efficiently simulated with few queries to the input.

Previous ZK-PCP constructions obtained an exponential gap between the query complexity $q$ of the honest verifier, and the bound $q^*$ on the queries of a malicious verifier (i.e., $q=polylog(q^*)$), but required either exponential-time simulation, or adaptive honest verification. This should be contrasted with standard PCPs, that can be verified non-adaptively (i.e., with a single round of queries to the proof). The problem of constructing such ZK-PCPs, even when $q^*=q$, has remained open since they were first introduced more than 2 decades ago. This question is also open for ZK-PCPPs, for which no construction with non-adaptive honest verification is known (not even with exponential-time simulation).

We resolve this question by constructing the first ZK-PCPs and ZK-PCPPs which simultaneously achieve efficient zero-knowledge simulation and non-adaptive honest verification. Our schemes have a square-root query gap, namely $q^*/q=O(sqrt(n))$ where $n$ is the input length.

Our constructions combine the "MPC-in-the-head" technique (Ishai et al., STOC `07) with leakage-resilient secret sharing. Specifically, we use the MPC-in-the-head technique to construct a ZK-PCP variant over a large alphabet, then employ leakage-resilient secret sharing to design a new alphabet reduction for ZK-PCPs which preserves zero-knowledge.

Hiring PhD student interns for this fall to work at Facebook AI Research (FAIR) on Homomorphic Encryption and related research in Private AI, PPML, Privacy in AI, and Fairness in AI. Fall internships will be remote, 16 weeks. Please contact me directly at klauter@fb.com to apply, time is short. Women and underrepresented minorities are encouraged to apply. https://ai.facebook.com/people/kristin-lauter/

Closing date for applications:

Contact: Dr. Kristin Lauter

More information: https://www.facebook.com/careers/v2/jobs/1973651836107576/

The Department of Computer Science at Technical University of Darmstadt invites applications for the position of a Full Professor (W3) for Cybersecurity.

We are looking for an outstanding scientist who will represent the topic area of cybersecurity in research and teaching. Successful candidates should demonstrate an outstanding scientific profile, with high-impact research contributions in the area of cybersecurity. A research profile that focuses on emerging application areas (e.g., machine learning & data science, IoT, decentralized systems) or on core topics of cybersecurity (e.g., hardware and network security, privacy) is desired. Successful collaboration in international research teams, with industry, or across research disciplines is desirable.

The professorship is expected to strengthen the department’s research focus on cybersecurity and offers the opportunity to participate in joint research projects currently running at Technical University of Darmstadt. This in particular includes the DFG Collaborative Research Center “CROSSING”, the National Research Center for Applied Cybersecurity ATHENE, and the Hessian Center for Artificial Intelligence.

In addition to excellent scientific credentials, we seek a strong commitment to teaching and experience in attracting third-party funding as well as participation in academic governance. The Technical University of Darmstadt has a strong focus on engineering science and information and communication technology. The Department of Computer Science is one of the leaders in research and teaching and regularly ranked among the top German departments.

Please submit applications in English with the usual attachments (CV including research and teaching achievements, list of publications, copies of diplomas) as well as a research and teaching statement, quoting the code number 221, to the Chair of the Department of Computer Science, Prof. Dr. Felix Wolf (dekanat@informatik.tu-darmstadt.de).

Further information: https://www.tu-darmstadt.de/universitaet/karriere_an_der_tu/stellenangebote/aktuelle_stellenangebote/stellenausschreibungen_detailansichten_1_40864

Closing date for applications:

Contact: Sebastian Faust, sebastian.faust@cs.tu-darmstadt.de

More information: https://www.tu-darmstadt.de/universitaet/karriere_an_der_tu/stellenangebote/aktuelle_stellenangebote/stellenausschreibungen_detailansichten_1_408640.en.jsp

The Cybersecurity and Data Analytics research group at the University of Mondragon is looking for qualified applicants for a PhD position in Post-Quantum Cryptography (PQC).

Currently standardized public key cryptography, upon which widely deployed secure internet protocols depend on, is vulnerable to Shor’s polynomial-time quantum algorithm for the factoring and discrete logarithm problems. Moreover, substantial advances in quantum computing in the past decade have re-assured the scientific community about the necessity to build quantum-resistant cryptosystems.

PQC has raised as the preferred solution to face the threat that quantum computers pose to secure communications systems. The ongoing standardization process run by the National Institute of Standards and Technology to define new standards for public-key encryption, digital signatures and key-exchange schemes has only augmented the attention towards PQC.

There exist several alternative problems to classical public key cryptography. Lattice-based cryptography, multivariate cryptography, hash-based cryptography schemes, isogeny-based cryptography and code-based cryptography can be used to design cryptosystems secure against both classical and quantum computers and are thus regarded as PQC algorithms.

There exist many paramount ingredients to take into account when considering the transition of secure internet protocols such as TLS, OpenVPN, or WireGuard to PQC. For instance, one of the main challenges that PQC raises is that, when compared to classical public key cryptography, its key sizes, ciphertext sizes or signature sizes, are often much larger. Also, the performance of PQC algorithms is generally worse than the one provided by present standards, and all these aspects vary depending on the specific PQC algorithm.

We are looking for students who are willing to conduct research on the impact of transitioning nowadays widely deployed secure internet protocols to post-quantum cryptography.

Closing date for applications:

Contact: Marc Manzano

There is a job opening for a senior scientist (i.e. a fixed-term, non-tenured assistant professor) at the Cybersecurity Research Group at AAU (Klagenfurt). AAU is a young university: in 2018 it was in the QS top 50 under 50 list; it ranked 6th of all Austrian Universities in 2020.

The lecturer position is fixed-term for 3.5 years. The successful applicant is expected to do a small amount of teaching (2-4 contact/lecture hours per week during term time, subject specific only i.e. no service teaching) whilst contributing to the wider research agenda of the Cybersecurity group.

The Cybersecurity group (www.cybersecurityresearch.at) was recently established by Prof. Elisabeth Oswald (ERC Cog, EPSRC Leadership fellow) after her move from Bristol (UK) to Austria. The group's core expertise is in applied aspects of cryptography, in particular with statistical techniques that deal with the detection and exploitation of information leakage. The group wants to expand its repertoire, e.g. towards data intensive aspects of cybersecurity more generally and therefore seeks to appoint somebody with a a background in statistics/data science/AI who has an interest in cybersecurity applications of their research; or towards other relevant areas of (applied) cryptography including embedded security.

The minimum monthly gross salary for this position amounts to € 3.9k (14 times per year) and can increase to € 4.5k (x14) maximum in the case of consideration of previous occupational experience. The fixed-term employment contract is expected to commence in August 2020 (but this is negotiable). All details can be found here: https://jobs.aau.at/en/job/senior-scientist-all-genders-welcome-2/.

Informal enquiries can be directly directed to Elisabeth . Oswald@aau.at Formal applications have to be made via the AAU jobs portal: https://jobs.aau.at/en/ AAU is an equal opportunities employer and therefor particularly encourages applications of female researcher and in general researchers from underrepresented groups.

Closing date for applications:

Contact: Elisabeth . Oswald @ aau . at

More information: https://jobs.aau.at/en/job/senior-scientist-all-genders-welcome-2/

CAP-TEE: Capability Architectures for Trusted Execution

Trusted Execution Environments (TEEs) shield computations using security-sensitive data (e.g. personal data, banking information, or encryption keys) inside a secure "enclave" from the rest of the untrusted operating system. A TEE protects its data and code even if an attacker has gained full root access to the untrusted parts of the system. In this project, we will use capability architectures (as e.g. developed by the CHERI project) to protect TEEs against such state-of-the-art attacks. We address a wide range of threats from software vulnerabilities such as buffer overflows to sophisticated hardware attacks like fault injection. CAP-TEE will provide a strong, open-source basis for the future generation of more secure TEEs: https://cap-tee.org/

The project is led by David Oswald. Our industrial project partners are also devoting time to the project, and the PhD student will have the opportunity to work with them.

The studentship covers a stipend and tuition fees based on UK home student rates (nb: the studentship does not cover the full tuition fees for overseas students.).

Candidates should have a good background in computer science. One focus will be on improving and evaluating the security of capabilty architectures; suitable candidates will hence need a strong background in system-level programming (e.g. using C or C++). We also expect a first-class UG or PG degree in a relevant subject (e.g. computer science or electrical engineering).

How to apply: There is no deadline for applying. The PhD candidate is expected to start in summer/autumn 2021. We will process applications as they arrive. To apply, please send your CV, a transcript with a list of courses and grades, and a description of your research interests to d.f.oswald (at) bham.ac.uk.

Closing date for applications:

Contact: Dr David Oswald

More information: https://www.cs.bham.ac.uk/~oswalddf/phd-projects.php

This is an exceptional opportunity to join the University of Manchester’s developing work in Cyber Security.

The Department of Computer Science is investing for growth in the Computer Science aspects of Information and Cyber Security. You will contribute to our portfolio of research and teaching in cyber security, and be willing to engage across discipline boundaries to apply your work. This will include engaging with a variety of business stakeholders and national agencies and government departments.

You will be part of a pan-university community contributing to Digital Trust and Security, including – but not restricted to – privacy, trust, data protection (School of Social Sciences), cybercrime, criminals, victims (School of Law) and work place security (Alliance Manchester Business School).

The Department of Computer Science is a leading research institution, and values exceptional researchers. You will publish to the highest standards, secure external research funding, pursue real-world impact, and contribute to the PGR training programmes within the Department.

The Department values exceptional teachers. You will play a key role in maintaining our reputation as an institute of learning – designing and delivering innovative undergraduate (UG) and postgraduate (PG) topics, not only in Cyber Security, but also across the spectrum of Computer Science. Exceptional teachers are encouraged to demonstrate this in their application.

Closing date for applications:

Contact: Enquiries about the vacancy, shortlisting and interviews: Name: Professor Robert Stevens

Email: robert.stevens@manchester.ac.uk

More information: https://www.jobs.manchester.ac.uk/displayjob.aspx?isPreview=Yes&jobid=20096

Event date: 1 September to 2 September 2021
Submission deadline: 12 June 2021
Notification: 24 July 2021

Event date: 15 November 2021
Submission deadline: 25 June 2021
Notification: 13 August 2021

The Herbert Wertheim College of Engineering at the University of Florida (UF) invites applications for a full-time, nine-month tenure track faculty position at the rank of Assistant/Associate/Full Professor in the Department of Electrical and Computer Engineering, or the Department of Computer & Information Sciences & Engineering (CISE). Candidates are sought whose research focuses on fully homomorphic encryption (FHE) and who are interested in collaborative research with the Florida Institute for Cybersecurity (FICS) Research, housed within the Herbert Wertheim College of Engineering. FICS Research is the nation’s premier multidisciplinary research institute focused on the advancement of cybersecurity with major partnerships and collaborations among industry, academe, and government. FICS Research covers all aspects of cybersecurity and assurance including hardware, network, mobile, big data, Internet of Things, applied crypto, social sciences, law, and more. The institute’s direct support of industry and government partners also enhances the educational experience and outcome for a diverse set of top-quality graduate and undergraduate students. Engineers and scientists interested in emerging FHE cryptographic applications and implementation will find a wealth of opportunities for supportive and multi-disciplinary collaboration in this position. The University of Florida is the flagship campus of the State of Florida university system and is ranked as the #6 best public US university according to US News and World Report. UF recently announced a $70 million artificial intelligence partnership with NVIDIA to create an AI-centric data center that houses the world's fastest AI supercomputer in higher education. Of particular relevance to this new faculty position, the HWCOE is in the process of creating the programmatic backbone to UF’s efforts to change the future of education and workforce development through university-wide AI training and experiential learning efforts. The Department of ECE in the HWCOE is a vibrant, multidisciplinary highly collaborative environment, consistently ranked among the top departments for both graduate and undergraduate progr

Closing date for applications:

Contact: tehranipoor@ufl.edu

More information: https://facultyjobs.hr.ufl.edu/posting/87357

About the Role: The candidate will be expected to research cryptographic protocols that will be useful in blockchain applications or more generally. They will additionally dedicate some fraction of their time to projects that more directly benefit Ethereum. There is a lot of flexibility to work on topics they find interesting and also to collaborate with other teams for example in academia. We have a culture of open source and no patents will be put on any work they produce. The role is remote. The position is permanent however the details of the contract will depend on the location and personal circumstances of the candidate.

Requirements: The successful candidate will have a PhD in either cryptography, consensus, or a closely related field. They will have a strong track record of publishing in top tier conferences and a clear vision of how they wish to continue their research for the benefit of blockchain and other communities. They will be comfortable working both independently and as part of a larger team. The candidate should be able to prototype their protocols/algorithms in a programming language of their choice.

The focus of this position is on Zero Knowledge Virtual Machines. Experience with the following is an advantage but not required:

• Zero-Knowledge proof schemes such as Pairing-based SNARKs (Groth16, PLONK), Bulletproofs, STARKs, etc.
• Different arithmetization schemes such as AIR, R1CS, PLONK.
• Different methods of implementing recursive SNARKs.
• Implementing RAM in SNARKs, e.g. TinyRAM.
• Knowledge of how virtual machines work and how to scale them.

Interested candidates that have more diverse skills but do not fit the above requirements should also consider applying as there may be other roles within the foundation.

Closing date for applications:

Contact: Please email cryptography@ethereum.org with a CV and a short document (either 1 or 2 pages) detailing how you have personally contributed to each of your publications. If you have contributed to any open source projects then additionally discuss this in the short document or provide links.