International Association
for Cryptologic Research

The Applied Cryptography Unit (https://groups.oist.jp/appcrypto) at the Okinawa Institute of Science and Technology (OIST) is seeking to hire up to four postdoctoral scholars in cryptography.

The Applied Cryptography Unit, led by Prof Carlos Cid, was established in 2022, to conduct research in the design and analysis of modern cryptographic primitives and schemes used to protect confidentiality and integrity of data, both in the classical and in the quantum settings. To forge and develop its research activities, we are now seeking to hire up to four outstanding post-doctoral researchers to work in the following topics: post-quantum / quantum cryptography (design and analysis), quantum cryptanalysis, post-quantum cryptographic techniques for privacy-preserving mechanisms.

The postdocs will be provided with funding and access to world-class facilities to pursue their research. The Unit aims to establish a highly collaborative environment, and we expect there will be several opportunities to work with other research groups at OIST, in Japan and overseas.

Submission Documents

Applicants should prepare a single pdf file with:

• Cover letter, outlining the motivation for applying for the position, research interests, experience and qualifications of relevance for the position;
• CV with a list of publications;
• Names and contact information of two referees, one of which should be a previous employer.

and submit it at https://www.oist.jp/careers/postdoctoral-scholars-applied-cryptography-unit

Application Deadline:

Applicants will be considered until the positions are filled, but submissions by 28 May 2023 will guarantee full consideration.

Closing date for applications:

Contact: Carlos Cid (carlos.cid@oist.jp)

More information: https://www.oist.jp/careers/postdoctoral-scholars-applied-cryptography-unit

iTrust is a Cyber Security Research Center in SUTD and a National Satellite of Excellence in Singapore for securing critical infrastructure. iTrust hosts the world-class cyber-physical system (CPS) testbeds which are used for research, education, training, live-fire exercise, and technology validation.

We offer PhD scholarship on cybersecurity in general and CPS security in particular (especially on IoT and maritime). The candidates should have an excellent background (with Bachelor or Master degree and CGPA>80%) in mathematics or computer science/engineering. Acquaintance with cryptography and network/system security concepts as well as some programming skills is preferred. Interested candidates please send your CV to Prof. Jianying Zhou or Prof. Sudipta Chattopadhyay. Only short-listed candidates will be contacted for interview.

Closing date for applications:

Contact: Prof. Jianying Zhou [jianying_zhou@sutd.edu.sg] or Prof. Sudipta Chattopadhyay [sudipta_chattopadhyay@sutd.edu.sg]

More information: https://itrust.sutd.edu.sg/

The Digital Security Department of EURECOM, Sophia-Antipolis France, invites applications for a PhD position.
Topic - Artificial Intelligence (AI) technologies can efficiently process large amounts of data, to help stakeholders improve their services and propose applications tailored to end-user needs. While the benefits of AI technologies for the society are manifold and range from personalized services to improved healthcare, their adoption remains unfortunately slow due to various obstacles among which the lack of trustworthiness. Indeed, the performance and robustness of AI technologies rely on the access to large datasets of good quality. Such datasets usually include privacy-sensitive information. In this context, Federated learning (FL) is emerging as a powerful paradigm to collaboratively train a machine-learning (ML) model among thousands or even millions of participants. FL inherently promises (some) privacy and governance guarantees for the clients because the training data never leaves the client’s premises. Nevertheless, the collaborative aggregation of models’ parameters can potentially expose clients' specific information, and opens up to security breaches with potential loss of privacy. The successful candidate will study, the privacy and security challenges associated with federated learning and design and evaluate scalable and efficient privacy-enhancing technologies for FL using advanced cryptographic techniques such as multi-key homomorphic encryption or multi-party computation.
Requirements - Applicants should hold a Master degree or equivalent in Computer Science or a closely related area with a strong background on cryptography. Some background in machine learning is appreciated.
The application requires, among other documents, a CV, a cover letter describing the applicant’s research interests, the contact details of 2/3 persons that can provide references about the candidate and the transcripts of courses taken at graduate (and optionally undergraduate) level.

Closing date for applications:

Contact: Applicants are invited to send their applications via e-mail under reference [PhD-FLP] to melek.onen@eurecom.fr

Dfns Labs, the research division of Dfns, seeks MS/Ph.D scholars with a substantial aptitude in applied cryptography for remote internships spanning 10-12 weeks. These internships encompass designing and implementing threshold cryptographic protocols. Opportunities for internships are available throughout the year, commencing in the summer of 2023. We welcome applications from individuals of diverse backgrounds with distinctive outlooks.

Dfns is a cybersecurity company that builds custody SaaS solutions for web3 apps. Dfns gives financial institutions and businesses—from fintechs to e-commerce sites—the freedom to own and transfer crypto using a battle-designed security infrastructure.

Job Description

Develop proof-of-concepts exhibiting common MPC, threshold cryptography, and zero-knowledge proof implementations.

Collaborate with the research and engineering team on technical research tasks.

Contribute to academic articles and blog posts.

Stay apprised of the newest advancements in crypto, DeFi, and blockchain.

Interact with a team of cryptographers and engineers to contribute to the company's research plan.

Basic Qualifications

Must be enrolled in a Ph.D. or Masters program in Computer Science or a related technical field.

Must possess formidable software engineering skills in common programming languages (e.g. C/C++, Rust (preferred), Python, Java).

Should possess a working knowledge of cryptography and privacy-enhancing technologies.

Must possess superior written and verbal communication skills.

Additional Information

Compensation: Attractive salary, equity options, paid time-off, etc.

Location: Hybrid – Home or Office-based

Closing date for applications:

Contact: Please send your CV to research-jobs@dfns.co
Contact Xianrui Meng (xm@dfns.co) and Jon Katz (jkatz@dfns.co) for more information.

Applications are invited for 6 Research Fellow posts to perform research in the area of AI-enabled cybersecurity. The posts are associated with the newly-created Cyber-AI Technologies Hub at CSIT, which is a collaboration with cyber security companies on projects in AI-enabled cyber security. The Cyber-AI Technologies Hub is a physical environment where companies and academia are co-located to collaborate on the advancement and demonstration of AI and cyber security.

Research Fellows will have the opportunity to advance research in areas such as: threat intelligence and monitoring, ICS malware detection and network intrusion detection, device trust, hardware/embedded systems security, security and verification of AI and threat prediction and prevention.

The successful candidates must have obtained, or be about to obtain, a PhD in engineering or physical sciences. At least 3 years’ high quality research experience in cybersecurity, and/or machine learning/AI, as evidenced by a strong track record of publications in leading journals and conferences in relevant areas.

Closing Date: 17/04/2023

Closing date for applications:

Contact: Paul Miller (p.miller@qub.ac.uk)

More information: https://hrwebapp.qub.ac.uk/tlive_webrecruitment/wrd/run/ETREC107GF.open?VACANCY_ID=411415IzIk&WVID=6273090Lgx&LANG=USA

Lattice-based cryptography has laid the foundation of various modern-day cryptosystems that cater to several applications, including post-quantum cryptography. For structured lattice-based schemes, polynomial arithmetic is a fundamental part. In several instances, the performance optimizations come from implementing compact multipliers due to the small range of the secret polynomial coefficients. However, this optimization does not easily translate to side-channel protected implementations since masking requires secret polynomial coefficients to be distributed over a large range. In this work, we address this problem and propose two novel generalized techniques, one for the number theoretic transform (NTT) based and another for the non-NTT-based polynomial arithmetic. Both these proposals enable masked polynomial multiplication while utilizing and retaining the small secret property.

For demonstration, we used the proposed technique and instantiated masked multipliers for schoolbook as well as NTT-based polynomial multiplication. Both of these can utilize the compact multipliers used in the unmasked implementations. The schoolbook multiplication requires an extra polynomial accumulation along with the two polynomial multiplications for a first-order protected implementation. However, this cost is nothing compared to the area saved by utilizing the existing cheap multiplication units. We also extensively test the side-channel resistance of the proposed design through TVLA to guarantee its first-order security.

A distributed oblivious RAM (DORAM) is a method for accessing a secret-shared memory while hiding the accessed locations. DORAMs are the key tool for secure multiparty computation (MPC) for RAM programs that avoids expensive RAM-to-circuit transformations.

We present new and improved 3-party DORAM protocols. For a logical memory of size $N$ and for each logical operation, our DORAM requires $O(\log N)$ local CPU computation steps. This is known to be asymptotically optimal. Our DORAM satisfies passive security in the honest majority setting. Our technique results with concretely-efficient protocols and does not use expensive cryptography (such as re-randomizable or homomorphic encryption). Specifically, our DORAM is 25X faster than the known most efficient DORAM in the same setting.

Lastly, we extend our technique to handle malicious attackers at the expense of using slightly larger blocks (i.e., $\omega(\log^2 N)$ vs. $\Omega(\log N)$). To the best of our knowledge, this is the first concretely-efficient maliciously secure DORAM.

Technically, our construction relies on a novel concretely-efficient 3-party oblivious permutation protocol. We combine it with efficient non-oblivious hashing techniques (i.e., Cuckoo hashing) to get a distributed oblivious hash table. From this, we build a full-fledged DORAM using a distributed variant of the hierarchical approach of Goldreich and Ostrovsky (J. ACM '96). These ideas, and especially the permutation protocol, are of independent interest.

Proof of Storage-time (PoSt) is a cryptographic primitive that enables a server to demonstrate non-interactive continuous avail- ability of outsourced data in a publicly verifiable way. This notion was first introduced by Filecoin to secure their Blockchain-based decentral- ized storage marketplace, using expensive SNARKs to compact proofs. Recent work [2] employs the notion of trapdoor delay function to address the problem of compact PoSt without SNARKs. This approach however entails statefulness and non-transparency, while it requires an expensive pre-processing phase by the client. All of the above renders their solution impractical for decentralized storage marketplaces, leaving the stateless trapdoor-free PoSt with reduced setup costs as an open problem. In this work, we present stateless and transparent PoSt constructions using probabilistic sampling and a new Merkle variant commitment. In the process of enabling adjustable prover difficulty, we then propose a multi- prover construction to diminish the CPU work each prover is required to do. Both schemes feature a fast setup phase and logarithmic verification time and bandwidth with the end-to-end setup, prove, and verification costs lower than the existing solutions

We revisit the problem of {\em reusable} non-interactive secure computation (NISC). A standard NISC protocol for a sender-receiver functionality $f$ enables the receiver to encrypt its input $x$ such that any sender, on input $y$, can send back a message revealing only $f(x,y)$. Security should hold even when either party can be malicious. A {\em reusable} NISC protocol has the additional feature that the receiver's message can be safely reused for computing multiple outputs $f(x,y_i)$. Here security should hold even when a malicious sender can learn partial information about the honest receiver's outputs in each session.

We present the first reusable NISC protocol for general functions $f$ that only makes a {\em black-box} use of any two-message oblivious transfer protocol, along with a random oracle. All previous reusable NISC protocols either made a non-black-box use of cryptographic primitives (Cachin et al., ICALP 2002) or alternatively required a stronger arithmetic variant of oblivious transfer and were restricted to $f$ in $\mathsf{NC}^1$ or similar classes (Chase et al., Crypto 2019). Our result is obtained via a general compiler from standard NISC to reusable NISC that makes use of special type of honest-majority protocols for secure multiparty computation.

Finally, we extend the above main result to reusable {\em two-sided} NISC, in which two parties can encrypt their inputs in the first round and then reveal different functions of their inputs in multiple sessions. This extension either requires an additional (black-box) use of additively homomorphic commitment or alternatively requires the parties to maintain a state between sessions.

Secure computation enables mutually distrusting parties to jointly compute a function on their secret inputs, while revealing nothing beyond the function output. A long-running challenge is understanding the required communication complexity of such protocols---in particular, when communication can be sublinear in the circuit representation size of the desired function. For certain functions, such as Private Information Retrieval (PIR), this question extends to even sublinearity in the input size.

We develop new techniques expanding the set of computational assumptions for sublinear communication in both settings:

1) [Circuit size] We present sublinear-communication protocols for secure evaluation of general layered circuits, given any 2-round rate-1 batch oblivious transfer (OT) protocol with a particular ``decomposability'' property. In particular, this condition can be shown to hold for the recent batch OT protocols of (Brakerski et al. Eurocrypt 2022), in turn yielding a new sublinear secure computation feasibility result: from Quadratic Residuosity (QR) together with polynomial-noise-rate Learning Parity with Noise (LPN). Our approach constitutes a departure from existing paths toward sublinear secure computation, all based on fully homomorphic encryption or homomorphic secret sharing.

2) [Input size.] We construct single-server PIR based on the Computational Diffie-Hellman (CDH) assumption, with polylogarithmic communication in the database input size $n$. Previous constructions from CDH required communication $\Omega(n)$. In hindsight, our construction comprises of a relatively simple combination of existing tools from the literature.

As zero-knowledge proofs gain increasing adoption, the cryptography community has designed domain-specific languages (DSLs) that facilitate the construction of zero-knowledge proofs (ZKPs). Many of these DSLs, such as Circom, facilitate the construction of arithmetic circuits, which are essentially polynomial equations over a finite field. In particular, given a program in a zero-knowledge proof DSL, the compiler automatically produces the corresponding arithmetic circuit. However, a common and serious problem is that the generated circuit may be underconstrained, either due to a bug in the program or a bug in the compiler itself. Underconstrained circuits admit multiple witnesses for a given input, so a malicious party can generate bogus witnesses, thereby causing the verifier to accept a proof that it should not. Because of the increasing prevalence of such arithmetic circuits in blockchain applications, several million dollars worth of cryptocurrency have been stolen due to underconstrained arithmetic circuits.

Motivated by this problem, we propose a new technique for finding ZKP bugs caused by underconstrained polynomial equations over finite fields. Our method performs semantic reasoning over the finite field equations generated by the compiler to prove whether or not each signal is uniquely determined by the input. Our proposed approach combines SMT solving with lightweight uniqueness inference to effectively reason about underconstrained circuits. We have implemented our proposed approach in a tool called $\mathbf{\mathsf{QED}^2}$ and evaluate it on 163 Circom circuits. Our evaluation shows that $\mathbf{\mathsf{QED}^2}$ can successfully solve 70\% of these benchmarks, meaning that it either verifies the uniqueness of the output signals or finds a pair of witnesses that demonstrate non-uniqueness of the circuit. Furthermore, $\mathbf{\mathsf{QED}^2}$ has found 8 previously unknown vulnerabilities in widely-used circuits.

The global supply chain involves multiple independent entities, and potential adversaries can exploit different attack vectors to steal proprietary designs and information. As a result, intellectual property (IP) owners and consumers have reasons to keep their designs private. Without a trusted third party, this mutual mistrust can lead to a deadlock where IP owners are unwilling to disclose their IP core before a financial agreement is reached, while consumers need assurance that the proprietary design will meet their integration needs without compromising the confidentiality of their test vectors. To address this challenge, we introduce an efficient framework called MPloC that resolves this deadlock by allowing owners and consumers to jointly evaluate the target design with consumer-supplied test vectors while preserving the privacy of both the IP core and the inputs. MPloC is the first work that combines secure multiparty computation (MPC) and logic-locking techniques to accomplish these goals. Our approach supports both semi-honest and malicious security models to allow users to balance stronger security guarantees with performance. We compare our approach to existing state-of-the-art works that utilize homomorphic encryption across several benchmarks and report runtime improvements of more than two orders of magnitude.

Tampering attack is the act of deliberately modifying the codeword to produce another codeword of a related message. The main application is to find out the original message from the codeword. Non-malleable codes are introduced to protect the message from such attack. Any tampering attack performed on the message encoded by non-malleable codes, guarantee that output is either completely unrelated or original message. It is useful mainly in the situation when privacy and integrity of the message is important rather than correctness. Unfortunately, standard version of non-malleable codes are used for one-time tampering attack. In literature, we show that it is possible to construct non-malleable codes from authenticated encryptions. But, such construction does not provide security when an adversary tampers the codeword more than once. Later, continuously non-malleable codes are constructed where an attacker can tamper the message for polynomial number of times. In this work, we propose a construction of continuously non-malleable code from authenticated encryption in 2-split-state model. Our construction provides security against polynomial number of tampering attacks and non-malleability property is preserved. The security of proposed continuously non-malleable code reduces to the security of underlying leakage resilient storage when tampering experiment triggers self-destruct.

The secret key of any encryption scheme that are stored in secure memory of the hardwired devices can be tampered using fault attacks. The usefulness of tampering attack is to recover the key by altering some regions of the memory. Such attack may also appear when the device is stolen or viruses has been introduced. Non-malleable codes are used to protect the secret information from tampering attacks. The secret key can be encoded using non-malleable codes rather than storing it in plain form. An adversary can apply some arbitrary tampering function on the encoded message but it guarantees that output is either completely unrelated or original message. In this work, we propose a computationally secure non-malleable code from leakage resilient authenticated encryption along with 1-more extractable hash function in split-state model with no common reference string (CRS) based trusted setup. Earlier constructions of non-malleable code cannot handle the situation when an adversary has access to some arbitrary decryption leakage (i.e., during decoding of the codeword) function to get partial information about the codeword. In this scenario, the proposed construction is capable of handling such decryption leakages along with tampering attacks.

There is an increasing interest in efficiently computing isogenies with a kernel of large-smooth size, for instance, as a building block for building secure Proof-of-Knowledge (PoK) with isogenies of degree equals a power of a small prime number. Another example corresponded to the attacks started by Castyck and Decru and followed up by Maino-Martindale and Robert, which require calculating isogenies over superspecial principally polarized abelian surfaces (superspecial PPAS). On the opposite side of cryptanalysis, some of the current state-of-the-art on safe isogeny-based PoK constructions extends to the case of superspecial PPAS, with the property that one could use smaller fields (e.g., 128, 192, and 256 bits).

This work presents a general framework that generalizes the situation of computing isogenies of the large-smooth degree to the context of quotient groups. More precisely, we abstract and propose a generalization of the strategy technique by Jao, De Feo, and Plût. Such a framework provides an efficient generic algorithm that easily applies to computing isogenies over superspecial PPAS when given the isogeny kernel. Additionally, our algorithm induces an efficient algorithm to perform the KernelToIsogeny procedure required in SQISignHD.

To illustrate the impact of optimal strategies, we draft our experiments on the isogenies over superspecial PPAS required in the Castryck-Decru attack (powers of two and three). Our experiments illustrate a decent speed up of 1.25x faster than the state-of-the-art (about 20% of savings). Our results should be viewed as proof-of-concept implementation and considered for optimized C-language implementations.

Despite recent breakthrough results in attacking SIDH, the CSIDH protocol remains a secure post-quantum key exchange protocol with appealing properties. However, for obtaining efficient CSIDH instantiations one has to resort to small secret keys. In this work, we provide novel methods to analyze small key CSIDH, thereby introducing the representation method ---that has been successfully applied for attacking small secret keys in code- and lattice-based schemes--- also to the isogeny-based world.

We use the recently introduced Restricted Effective Group Actions ($\mathsf{REGA}$) to illustrate the analogy between CSIDH and Diffie-Hellman key exchange. This framework allows us to introduce a $\mathsf{REGA}\text{-}\mathsf{DLOG}$ problem as a level of abstraction to computing isogenies between elliptic curves, analogous to the classic discrete logarithm problem. This in turn allows us to study $\mathsf{REGA}\text{-}\mathsf{DLOG}$ with ternary key spaces such as $\{-1, 0, 1\}^n, \{0,1,2\}^n$ and $\{-2,0,2\}^n$, which lead to especially efficient, recently proposed CSIDH instantiations. The best classic attack on these key spaces is a Meet-in-the-Middle algorithm that runs in time $3^{0.5 n}$, using also $3^{0.5 n}$ memory.

We first show that $\mathsf{REGA}\text{-}\mathsf{DLOG}$ with ternary key spaces $\{0,1,2\}^n$ or $\{-2,0,2\}^n$ can be reduced to the ternary key space $\{-1,0,1\}^n$.

We further provide a heuristic time-memory tradeoff for $\mathsf{REGA}\text{-}\mathsf{DLOG}$ with keyspace $\{-1,0,1\}^n$ based on Parallel Collision Search with memory requirement $M$ that under standard heuristics runs in time $3^{0.75 n}/M^{0.5}$ for all $M \leq 3^{n/2}$. We then use the representation technique to heuristically improve to $3^{0.675n}/M^{0.5}$ for all $M \leq 3^{0.22 n}$, and further provide more efficient time-memory tradeoffs for all $M \leq 3^{n/2}$.

Although we focus in this work on $\mathsf{REGA}\text{-}\mathsf{DLOG}$ with ternary key spaces for showing its efficacy in providing attractive time-memory tradeoffs, we also show how to use our framework to analyze larger key spaces $\{-m, \ldots, m\}^n$ with $m = 2,3$.

Post-Quantum cryptography (PQC), in the past few years, constitutes the main driving force of the quantum resistance transition for security primitives, protocols and tools. TLS is one of the widely used security protocols that needs to be made quantum safe. However, PQC algorithms TLS integration introduce various implementation overheads compared to traditional TLS that in battery powered embedded devices with constrained resources, cannot be overlooked. While there exist several works, evaluating the PQ TLS execution time overhead in embedded systems there are only a few that explore the PQ TLS energy consumption cost. In this paper, a thorough power/energy consumption evaluation and analysis of PQ TLS 1.3 embedded system implementation has been made. A WolfSSL PQ TLS 1.3 custom implementation is used that integrates all the NIST PQC algorithms selected for standardization as well as those evaluated in NIST Round 4. The BSI recommendations have also been included. The various PQ TLS versions are deployed in a STM Nucleo evaluation board under a mutual and a unilateral client-server authentication scenario. The power and energy consumption collected results are analyzed in detail. The performed comparisons and overall analysis provide very interesting results indicating that the choice of the PQC algorithm TLS 1.3 combination to be deployed on an embedded system may be very different depending on the device use as an authenticated or not authenticated, client or server. Also, the results indicate that in some cases, PQ TLS 1.3 implementations can be equally or more energy consumption efficient compared to traditional TLS 1.3.

Spiking neural networks gain attention due to low power properties and event-based operation, making them suitable for usage in resource constrained embedded devices. Such edge devices allow physical access opening the door for side-channel analysis. In this work, we reverse engineer the parameters of a feed-forward spiking neural network implementation with correlation power analysis. Localized measurements of electro-magnetic emanations enable our attack, despite inherent parallelism and the resulting algorithmic noise of the network. We provide a methodology to extract valuable parameters of integrate-and-fire neurons in all layers, as well as the layer sizes.

Homomorphic encryption requires the homomorphism of encrypted ciphertext, and the operation between ciphertexts can be reflected in plaintexts. Fully homomorphic encryption requires that the encryption algorithm can satisfy additive homomorphism and multiplicative homomorphism at the same time. At present, there are many fully homomorphic encryption schemes, such as fully homomorphic encryption based on ideal lattices, AGCD problem, LWE problem, RLWE problem, and so on. But the improvement of efficiency, length of ciphertext, and calculation limit of the fully homomorphic encryption scheme are still problems that need further study.

Based on Lagrangian interpolation polynomials, we propose a fully homomorphic encryption scheme according to the difficulty of finding roots of a polynomial with the degree of at least two(mod n=p*q, p, q are both private large primes). We reasonably construct polynomials $trap_1$ and $trap_0$ to generate the ciphertext of message m, so that calculation between ciphertexts can directly act on plaintexts. Our scheme is safe as long as the Rabin encryption algorithm cannot be cracked.

Homomorphic encryption (HE) enables calculating on encrypted data, which makes it possible to perform privacy- preserving neural network inference. One disadvantage of this technique is that it is several orders of magnitudes slower than calculation on unencrypted data. Neural networks are commonly trained using floating-point, while most homomorphic encryption libraries calculate on integers, thus requiring a quantisation of the neural network. A straightforward approach would be to quantise to large integer sizes (e.g., 32 bit) to avoid large quantisation errors. In this work, we reduce the integer sizes of the networks, using quantisation-aware training, to allow more efficient computations. For the targeted MNIST architecture proposed by Badawi et al., we reduce the integer sizes by 33% without significant loss of accuracy, while for the CIFAR architecture, we can reduce the integer sizes by 43%. Implementing the resulting networks under the BFV homomorphic encryption scheme using SEAL, we could reduce the execution time of an MNIST neural network by 80% and by 40% for a CIFAR neural network.