International Association
for Cryptologic Research

Threshold fully homomorphic encryption provides efficient multi-party computation with low round-complexity. Among fully homomorphic encryption schemes, CKKS (Cheon-Kim-Kim-Song) enables high-throughput computations on both approximate and exact data. As most interesting applications involve deep computations, they require bootstrapping, the most efficient variants of which rely on sparse ternary secret keys. Unfortunately, so far, key generation protocols for threshold-CKKS either assume a trusted dealer, or lead to dense and non-ternary secret keys that severely damage computational throughput. In the latter case, the impact is so large that one often considers off-loading bootstrapping to an interactive protocol [Mouchet et al., PETS'21].

We introduce a novel Distributed Key Generation (DKG) protocol for threshold-CKKS. At a high level, it consists in running the existing distributed key generation algorithm from Mouchet et al. resulting in large secret keys, and using it to homomorphically evaluate the sparse-secret key generation algorithm. At the end, the parties obtain additive shares of a sparse secret key. The main technical challenge is to obtain an algorithm for sampling sparse ternary vectors of prescribed Hamming weight that can be CKKS-evaluated in an efficient manner. In the process, we design a new sampler of one-hot vectors that outperforms the one from [Boneh et al., AFT'20]. We also design a rejection-sampling algorithm to map several one-hot vectors into a vector of prescribed Hamming weight. The whole process can be performed with only two CKKS bootstraps, even for a significant number of users.

We present several variants of the DKG protocol, with~2 to~4 communication rounds, as well as an extension to key generation delegation. We implemented the 4-round protocol; its computational components run in 2.13s on GPU (RTX4090).

Quantum cryptography is a rapidly-developing area which leverages quantum information to accomplish classically-impossible tasks. In many of these protocols, quantum states are used as long-term cryptographic keys. Typically, this is to ensure the keys cannot be copied by an adversary, owing to the quantum no-cloning theorem. Unfortunately, due to quantum state's tendency to decohere, persistent quantum memory will likely be one of the most challenging resources for quantum computers. As such, it will be important to minimize persistent memory in quantum protocols.

In this work, we consider the case of one-shot signatures (OSS), and more general quantum signing tokens. These are important unclonable primitives, where quantum signing keys allow for signing a single message but not two. Naturally, these quantum signing keys would require storage in long-term quantum memory. Very recently, the first OSS was constructed in a classical oracle model and also in the standard model, but we observe that the quantum memory required for these protocols is quite large. In this work, we significantly decrease the quantum secret key size, in some cases achieving asymptotically optimal size. To do so, we develop novel techniques for proving the security of cryptosystems using coset states, which are one of the main tools used in unclonable cryptography.

This paper is about the proximity gaps phenomenon for Reed-Solomon codes. Very roughly, the proximity gaps phenomenon for a code $\mathcal C \subseteq \mathbb F_q^n$ says that for two vectors $f,g \in \mathbb F_q^n$, if sufficiently many linear combinations $f + z \cdot g$ (with $z \in \mathbb F_q$) are close to $\mathcal C$ in Hamming distance, then so are both $f$ and $g$, up to a proximity loss of $\varepsilon^*$.

Determining the optimal quantitative form of proximity gaps for Reed--Solomon codes has recently become of great interest because of applications to interactive proofs and cryptography, and in particular, to scalable transparent arguments of knowledge (STARKs) and other modern hash based argument systems used on blockchains today.

Our main results show improved positive and negative results for proximity gaps for Reed-Solomon codes of constant relative distance $\delta \in (0,1)$.

1. For proximity gaps up to the unique decoding radius $\delta/2$, we show that arbitrarily small proximity loss $\varepsilon^* > 0$ can be achieved with only $O_{\varepsilon^*}(1)$ exceptional $z$'s (improving the previous bound of $O(n)$ exceptions). 2. For proximity gaps up to the Johnson radius $J(\delta)$, we show that proximity loss $\varepsilon^* = 0$ can be achieved with only $O(n)$ exceptional $z$'s (improving the previous bound of $O(n^2)$ exceptions). This significantly reduces the soundness error in the aforementioned arguments systems.

3. In the other direction, we show that for some Reed--Solomon codes and some $\delta$, proximity gaps at or beyond the Johnson radius $J(\delta)$ with arbitrarily small proximity loss $\varepsilon^*$ needs to have at least $\Omega(n^{1.99})$ exceptional $z$'s.

4. More generally, for all constants $\tau$, we show that for some Reed-Solomon codes and some $\delta = \delta(\tau)$, proximity gaps at radius $\delta - \Omega_{\tau}(1)$ with arbitrarily small proximity loss $\varepsilon^*$ needs to have $n^{\tau}$ exceptional $z$'s.

5. Finally, for all Reed-Solomon codes, we show that improved proximity gaps imply improved bounds for their list-decodability. This shows that improved bounds on the list-decoding radius of Reed-Solomon codes is a prerequisite for any new proximity gaps results beyond the Johnson radius.

Reed-Solomon (RS) codes were recently shown to exhibit an intriguing $\textit{proximity gap}$ phenomenon. Specifically, given a collection of strings with some algebraic structure (such as belonging to a line or affine space), either all of them are $\delta$-close to RS codewords, or most of them are $\delta$-far from the code. Here $\delta$ is the proximity parameter which can be taken to be the Johnson radius $1-\sqrt{R}$ of the RS code ($R$ being the code rate), matching its best known list-decodability. Proximity gaps play a crucial role in the soundness analysis of Interactive Oracle Proof (IOP) protocols used in Succinct Non-Interactive Arguments of Knowledge (SNARKs) and the resulting proof sizes.

Proving proximity gaps beyond the Johnson radius, and in particular approaching $1-R$ (which is best possible), has been posed multiple times as a challenge with significant practical consequences to the efficiency of SNARKs. Here we prove that variants of RS codes, such as folded RS codes and univariate multiplicity codes, indeed have proximity gaps for $\delta$ approaching $1-R$. The result applies more generally to codes with a certain subspace-design property. Our proof hinges on a clean property we abstract called line (or more generally curve) decodability, which we establish leveraging and adapting techniques from recent progress on list-decoding such codes. Importantly, our analysis avoids the heavy algebraic machinery used in previous works, and requires a field size only linear in the block length.

The behavior of subspace-design codes w.r.t ``local properties'' has recently been shown to be similar to random linear codes and random RS codes (where the evaluation points are chosen at random from the underlying field). We identify a local property that implies curve decodability, and thus also proximity gaps, and thereby conclude that random linear and random RS codes also exhibit proximity gaps up to the $1-R$ bound. Our results also establish the stronger (mutual) correlated agreement property which implies proximity gaps. Additionally, we also a show a $\textit{slacked}$ proximity gap theorem for constant-sized fields using AEL-based constructions and local property techniques.

Fault attacks have historically been one of the most popular gray-box attacks in Cryptographic literature. In such attacks, an attacker tries to inject perturbations while executing a cipher and exploit the faulty outputs to recover the key. While the efficiency of such an attack is measured by number of faults required and size of the reduced key-space, another pivotal temporal parameter in the point of fault injection which has not received considerable attention. In this work, we plug this gap for a special class of ciphers namely DEFAULT and BAKSHEESH which boast of an SBox with one or more linear structures (LS). We make new observations which lead to the improvement of Division Property based fault attacks (DIFA) introduced by Kundu et al. in ACNS 2023. We show that these linear structures are particularly responsible for giving the higher fault penetration in these ciphers. We improve the state-of-the-art for BAKSHEESH from 30 to 28 rounds and for DEFAULT from 75 to 72 using the single round random nibble fault model. While for BAKSHEESH we are able to uniquely recover the key, for DEFAULT, we are able to reduce the key-space to $2^{64}$. This leads to the best fault attacks on BAKSHEESH and DEFAULT in terms of number of rounds penetrated for fault injection. Our work reiterates the fact that a property induced (in this case LS in SBox)) for some particular Cryptographic purposes (like fault attack resistance) may manifest orthogonally for another (increasing fault penetration) and thus adds value to block cipher design space exploration and fault attack counter-measure development.

The rapid advancements in quantum computing pose a significant threat to widely used cryptographic standards such as RSA and Elliptic-Curve Diffie-Hellman (ECDH), which are fundamental to securing digital communications and protecting sensitive data worldwide. The increasing feasibility of "harvest now, decrypt later" strategies where adversaries collect encrypted data today with the intent of decrypting it once quantum computing reaches sufficient maturity underscores the urgency of transitioning toward quantum-resistant cryptographic solutions. A pragmatic approach to maintaining security during this transitional period is the adoption of hybrid cryptographic techniques, which integrate traditional cryptographic mechanisms with post-quantum cryptography (PQC) and Quantum Key Distribution (QKD).

This paper presents a comprehensive review of hybrid cryptographic approaches, focusing on their incorporation into widely adopted security protocols such as TLS 1.3 and QUIC. We examine the key challenges associated with deploying hybrid cryptography, including performance trade-offs, security guarantees, and compatibility with existing infrastructure. Beyond protocol-level implementations, we explore the initiatives undertaken by global standardization bodies and leading technology firms to facilitate a seamless transition toward a quantum-secure future. By analyzing current strategies and insights from early adopters, we identify the critical factors that organizations must consider to effectively implement hybrid cryptographic solutions, ensuring resilience against emerging cryptographic threats.

A generator is a function that maps a random seed to a list of coefficients. We study generators that preserve distance to a linear code: the linear combination of any list of vectors using coefficients sampled by the generator has distance to the code no smaller than that of the original vectors, except for a small error. Distance preservation plays a central role in modern probabilistic proofs, and has been formalized in several ways. We study \emph{mutual correlated agreement}, the strongest known form of distance preservation.

We initiate the systematic study of mutual correlated agreement, aiming to characterize the class of generators with this property. Towards this, we study polynomial generators, a rich class that includes all examples of generators considered in the distance preservation literature. Our main result is that \emph{all polynomial generators guarantee mutual correlated agreement for every linear code}. This improves on prior work both in generality (the class of generators covered) and in parameters (the error bounds).

We additionally provide new results for the case where the linear code is a Reed--Solomon code, which is of particular interest in applications. We prove that all polynomial generators satisfy mutual correlated agreement for Reed–Solomon codes up to the Johnson bound. In particular, we improve upon the state-of-the-art by Ben-Sasson, Carmon, Ishai, Kopparty, and Saraf (FOCS 2020) and resolve a question posed by Arnon, Chiesa, Fenzi, and Yogev (Eurocrypt 2025).

Along the way we develop a flexible and general toolbox for mutual correlated agreement, are the first to establish distance preservation for generators that lie beyond polynomial generators.

In our increasingly interconnected world, the security of embedded devices plays a critical role in protecting sensitive information. Evaluating this security requires a meticulous examination of how cryptographic processes are implemented within the hardware of these devices. One widely employed technique for this purpose is Power Side Channel Analysis. At the heart of Correlation Power Side Channel Analysis lies the concept of the power consumption model, which helps to simulate power consumption while executing cryptographic operations on hardware. In this model, along with the hypothetical secret key, is correlated with the actual power consumption during the execution of a cryptographic operation under an unknown secret key. This approach enables the detection of potential vulnerabilities in cryptographic implementations. In this research, we introduce a novel power leakage model called the Technology library Power Leakage Model. This model is rooted in semiconductor technology. By aligning our model closely with specific semiconductor technology, we achieve a more realistic representation of power consumption. Our study provides compelling evidence for the effectiveness of the Power Leakage Model. We successfully extracted secret keys from an AES implementation using Correlation Power Analysis (CPA). Importantly, our Power Leakage Model can be adapted to accommodate various semiconductor technologies such as $55nm$ or $14nm$ technologies. In this work, we also compared the newly proposed leakage model with the Hamming Distance model and empirically evaluated that both models perform similarly when linear correlation techniques are used in CPA.

A $K$-multi-collision-resistant hash function ($K$-MCRH) is a shrinking keyed function for which it is computationally infeasible to find $K$ distinct inputs that map to the same output under a randomly chosen hash key; the case $K = 2$ coincides with the standard definition of collision-resistant hash function (CRH). A natural question is whether $K$-MCRH implies CRH for $K \geq 3$, as noted by Komargodski, Naor, and Yogev (EUROCRYPT 2018) and also by Jain, Li, Robere, and Xun (FOCS 2024).

We resolve this question for all constant $K$, showing that there is no black-box construction of $K$-MCRH from $(K + 1)$-MCRH for all constant $K \geq 2$. We also show that there is no black-box construction of distributional CRH (which is another relaxation of CRH) from 3-MCRH, answering an open question posed by Komargodski and Yogev (CRYPTO 2018) and also by Berman, Degwekar, Rothblum, and Vasudevan (EUROCRYPT 2018). Besides applications in cryptography, our separation also implies black-box separations between TFNP search problems, which are related to problems in proof complexity and other areas.

We introduce time-lock encrypted storage (tTLES), a storage service provided by blockchains. In tTLES, clients store encrypted values towards a future decryption time $\tau_{tgt}$ (measured in block height). The security of tTLES requires that a value is decrypted only if (i) the encrypted value is included in the blockchain, and (ii) the time $\tau_{tgt}$ has passed. This is crucially different from existing schemes, which only enforce either of these conditions but not both. We formalize tTLES, and present an efficient protocol that relies on (in a black-box manner) a threshold identity-based encryption scheme, and a recent batch threshold decryption scheme. Finally, we discuss various applications that will benefit from tTLES.

Obliviousness has been regarded as an essential property in encrypted databases (EDBs) for mitigating leakage from access patterns. Yet despite decades of work, practical oblivious graph processing remains an open problem. In particular, all existing approaches fail to enable the design of index-free adjacency (IFA), i.e., each vertex preserves the physical positions of its neighbors. However, IFA has been widely recognized as necessary for efficient graph processing and is fundamental in native graph databases (e.g., Neo4j).

In this work, we propose a core technique named delayed duplication to resolve the conflict between IFA and obliviousness. To the best of our knowledge, we are the first to address this conflict with both practicality and strict security. Based on the new technique, we utilize elaborate data structures to develop a new EDB named Grove for processing expressive graph queries. The experimental results demonstrate that incorporating IFA makes Grove impressively outperform the state-of-the-art work across multiple graph-processing tasks, such as the well-known neighbor query and $t$-hop query.

Event date: 2 June 2026
Submission deadline: 13 February 2026
Notification: 16 March 2026

Event date: 2 June 2026
Submission deadline: 20 January 2026
Notification: 9 March 2027

The candidate will work on (quantum-)computational and mathematical aspects of lattice-based or isogeny-based cryptography. They will join the Number Theory team at ENS de Lyon, supported by grant ANR-22-PNCQ-0002 (the HQI initiative).

The candidate should hold a PhD degree in Mathematics or Computer Science and have a strong research record in any of the following areas: number theory, quantum computing, lattice-based cryptography, or isogeny-based cryptography.

Applications should be sent to Benjamin Wesolowski at postdoc.hqi.wiring373@passmail.net (including a CV, cover letter, and list of references).

Closing date for applications:

Contact: Benjamin Wesolowski, postdoc.hqi.wiring373@passmail.net

A postdoc position is available in the Cryptology and Data Security research group at the Institute of Computer Science, University of Bern, led by Christian Cachin.

Our research addresses all aspects of security in distributed systems, especially cryptographic protocols, consistency, consensus, and cloud-computing security. We are particularly interested in blockchains, distributed ledger technology, cryptocurrencies, and their security and economics. Please explore crypto.unibe.ch to learn more about our research topics. We are part of IC3: The Initiative for Cryptocurrencies and Contracts (https://www.initc3.org/).

This position concerns smart contracts running on blockchains with a cryptocurrency, blockchain consensus protocols, transactions, and concurrent execution of programs. The candidate is expected to develop novel methods and protocols for scaling blockchains.

Please follow this link for full information on how to apply: https://crypto.unibe.ch/jobs/

Closing date for applications:

Contact: Christian Cachin (https://crypto.unibe.ch/cc)

More information: https://crypto.unibe.ch/jobs/

Multiple Ph.D. positions are available in the Cryptology and Data Security research group at the Institute of Computer Science, University of Bern, led by Christian Cachin.

Our research addresses all aspects of security in distributed systems, especially cryptographic protocols, consistency, consensus, and cloud-computing security. We are particularly interested in blockchains, distributed ledger technology, cryptocurrencies, and their security and economics. Please explore crypto.unibe.ch to learn more about our research topics. We are part of IC3: The Initiative for Cryptocurrencies and Contracts (https://www.initc3.org/).

These positions concern smart contracts running on blockchains with a cryptocurrency, blockchain consensus protocols, transactions, and concurrent execution of programs. Candidates are expected to investigate novel methods and protocols for scaling blockchains.

Please follow this link for full information on how to apply: https://crypto.unibe.ch/jobs/

Closing date for applications:

Contact: Christian Cachin (https://crypto.unibe.ch/cc)

More information: https://crypto.unibe.ch/jobs/

Project Manager – National Quantum Mission (IIT Bhilai)

Applications are invited for the position of Project Manager under the DST–National Quantum Mission project titled “Development of tamper-proof SCA/FI resistant 10Gbps post-quantum In-line IP network encryptor, Post-Quantum TLS ASIC (PQ-TLS), and TLS Accelerator PCIe card using PQ-TLS ASIC.”

Position: Project Manager (01 post)
Duration: 1 year (extendable annually)
Salary: ₹80,000 (consolidated)
Age limit: 50 years

Essential Qualification:
PhD or ME/MTech with ≥4 years relevant experience, or BE/BTech with ≥7 years relevant experience in CSE/IT/ECE/Mathematics or related fields.

Desirable:
Strong background in Mathematics, Cryptography, and Programming; experience in project coordination and team leadership; ability to manage multiple tasks and meet deadlines. Experience with NIST Post-Quantum Standard Algorithms and/or Fault Analysis of Crypto algorithms with ChipWhisperer platform is a plus.

Principal Investigator:
Dr. Dhiman Saha, Assistant Professor, CSE, IIT Bhilai
Email: dhiman@iitbhilai.ac.in

How to Apply:
Submit the filled application form and CV to decipheredlab@iitbhilai.ac.in with the subject line “Application for Project Manager (NQM)”.


Important Dates:
Application deadline: 01 December 2025
Interview date: 15 December 2025 (11:00 AM, Room 413B, ED-1 Building, IIT Bhilai)

Closing date for applications:

Contact: Dr. Dhiman Saha
Dept. of CSE, ED-1 Building
IIT Bhilai, CG, INDIA, 491002
http://dhimans.in/
http://de.ci.phe.red

More information: https://www.iitbhilai.ac.in/index.php?pid=adv_nov25_04

The Department of Computer Science (CS) at the University of Alabama at Birmingham (UAB) is seeking candidates with expertise in cyber security for a tenured associate professor position holding the Phyllis and David Brasfield Endowed Faculty Scholarship, starting Fall 2026.

The CS Department at UAB offers PhD, MS, BS, and BA programs. For additional information about the Department, please visit: https://www.uab.edu/cas/computerscience/. UAB is a Carnegie R1 research university, Alabama’s single largest employer, and an engine of revitalization for Birmingham, the largest city in Alabama.

For the complete job announcement and application procedures, see: https://uab.peopleadmin.com/postings/26352

Closing date for applications:

Contact: For more information, please contact the search committee chair Dr. John Johnstone (jkj@uab.edu).

More information: https://uab.peopleadmin.com/postings/26352

We disprove a range of conjectures for Reed-Solomon codes underpinning the security and efficiency of many modern proof systems, including SNARKs based on FRI (Ben-Sasson-Bentov-Horesh-Riabzev, ICALP’18), DEEP-FRI (Ben-Sasson-Goldberg-Kopparty-Saraf, ITCS’20), STIR (Arnon-Chiesa-Fenzi-Yogev, CRYPTO’24), and WHIR (Arnon-Chiesa-Fenzi-Yogev, preprint). Concretely, we prove that the following conjectures are false:

1. The correlated agreement up-to-capacity conjecture of Ben-Sasson-Carmon-Ishai-Kopparty-Saraf (J. ACM’23), 2. The mutual correlated agreement up-to-capacity conjecture of WHIR, 3. The list-decodability up-to-capacity conjecture of DEEP-FRI, which follows from existing results in the literature.

We then propose minimal modifications to these conjectures up to the list-decoding capacity bound.

Our second main contribution is a proof that correlated agreement with small enough error probability implies list decoding of Reed-Solomon codes. Thus, any future results on our correlated agreement conjectures with small enough error probability would imply similar results in classical list decoding. A reduction from proximity gaps to list-decodability was heretofore a natural open problem.

Post-Quantum key encapsulation mechanisms based on the re-encryption framework of Fujisaki and Okamoto have proved very sensitive to Plaintext Checking Oracle (PCO) attacks. The first theoretic works on PCO attacks were rapidly followed by practical attacks on real implementations, notably on NIST standardized ML-KEM. The actual realization of a PCO relies on side-channel leakages that are inherently noisy ; even more so if the implementation embeds side-channel countermeasures. In this paper we tackle the often overlooked complications caused by highly noisy PCOs. We demonstrate that the impact of wrong oracle answers can be very efficiently reduced with the use of the so-called Sequential Probability Ratio Test (SPRT). This test can be seen as an elegant and natural early abort strategy on top of the commonly used approaches based on majority-voting or the likelyhood ratio test. As far as we know, this is the first use of SPRT in the context of side-channel attacks. We show that it allows to divide by a factor up to 3 the attack complexity compared to the traditional approaches. By establishing new comparisons with recently published noisy PCO attacks we emphasize that SPRT should be considered as the novel baseline for all future works in this line of research.