IACR News
Here you can see all recent updates to the IACR webpage. These updates are also available:
09 February 2024
Pedro Branco, Russell W. F. Lai, Monosij Maitra, Giulio Malavolta, Ahmadreza Rahimi, Ivy K. Y. Woo
In this work, we propose a new model for traitor-tracing systems where, instead of having a key authority, users could generate and register their own public keys. The public parameters are computed by aggregating all user public keys. Crucially, the aggregation process is \emph{public}, thus eliminating the need of any trusted authority. We present two new traitor-tracing systems in this model based on bilinear pairings. Our first scheme is proven adaptively secure in the generic group model. This scheme features a transparent setup, ciphertexts consisting of $6\sqrt{L}+4$ group elements, and a public tracing algorithm. Our second scheme supports a bounded collusion of traitors and is proven selectively secure in the standard model. Our main technical ingredients are new registered functional encryption (RFE) schemes for quadratic and linear functions which, prior to this work, were known only from indistinguishability obfuscation. To substantiate the practicality of our approach, we evaluate the performance a proof of concept implementation. For a group of $L = 1024$ users, encryption and decryption take roughly 50ms and 4ms, respectively, whereas a ciphertext is of size 6.7KB.
Dung Bui, Geoffroy Couteau, Pierre Meyer, Alain Passelègue, Mahshid Riahinia
06 February 2024
Engineering Department, Horizen Labs, Remote
We are looking for a talented and motivated engineer who will contribute to building the cryptographic infrastructure of our Web 3.0-enabled blockchain ecosystem. You will be involved in the design and implementation of blockchain scaling solutions, primarily based on zero-knowledge cryptography, with the aim of dramatically reducing the costs that blockchain operators incur when deploying their products. Our international team works in a stimulating and innovative environment, where technical expertise and experience contribute to the development of cutting-edge blockchain technology. You will be joining a small, deeply driven team of highly technical minds in a culture of openness, pragmatism, and ownership of challenging problems that span software engineering, systems design, cryptography, and computing.
What You’ll Own- Design and implementation of blockchain-based cryptographic solutions leveraging modern cryptography (ZK, MPC, FHE).
- Assume technical responsibility of novel systems while identifying areas for innovative research and development.
- Writing reusable, testable, and efficient code with a focus on best practices and security.
- Help shape the future of the company where you will be intimately involved in the strategic decision making process and immediately see the impact of your contributions.
- Attend conferences and find opportunities in the on-chain ecosystem.
Closing date for applications:
Contact: People & Talent Team - recruiting@horizenlabs.io
More information: https://boards.greenhouse.io/horizenlabs/jobs/5075393004
Qiaohan Chu, Li Lin, Chen Qian, Jie Chen
Panos Kampanakis, Will Childs-Klein
Quang Dao, Aayush Jain
In this work, we propose a new code-based assumption: Dense-Sparse LPN, that falls in the complexity class $\mathcal{BPP}^{\mathcal{SZK}}$ and is conjectured to be secure against subexponential time adversaries. Our assumption is a variant of LPN that is inspired by McEliece's cryptosystem and random $k\mbox{-}$XOR in average-case complexity. Roughly, the assumption states that \[(\mathbf{T}\, \mathbf{M}, \mathbf{s} \,\mathbf{T}\, \mathbf{M} + \mathbf{e}) \quad \text{is indistinguishable from}\quad (\mathbf{T} \,\mathbf{M}, \mathbf{u}),\] for a random (dense) matrix $\mathbf{T}$, random sparse matrix $\mathbf{M}$, and sparse noise vector $\mathbf{e}$ drawn from the Bernoulli distribution with inverse polynomial noise probability.
We leverage our assumption to build lossy trapdoor functions (Peikert-Waters STOC 08). This gives the first post-quantum alternative to the lattice-based construction in the original paper. Lossy trapdoor functions, being a fundamental cryptographic tool, are known to enable a broad spectrum of both lossy and non-lossy cryptographic primitives; our construction thus implies these primitives in a generic manner. In particular, we achieve collision-resistant hash functions with plausible subexponential security, improving over a prior construction from LPN with noise rate $\frac{\log^2 n}{n}$ that is only quasi-polynomially secure.
Randy Kuang
Helger Lipmaa, Roberto Parisella, Janno Siim
Zeyu Liu, Yunhao Wang
In this work, we inspect the BGV/BFV bootstrapping procedure from a different angle. We provide a generalized bootstrapping definition that relaxes the correctness requirement of regular bootstrapping, allowing constructions that support only certain kinds of circuits with arbitrary depth. In addition, our definition captures a form of functional bootstrapping. In other words, the output encrypts a function evaluation of the input instead of the input itself. Under this new definition, we provide a bootstrapping procedure supporting different types of functions. Our construction is 1-2 orders of magnitude faster than the state-of-the-art BGV/BFV bootstrapping algorithms, depending on the evaluated function. Of independent interest, we show that our technique can be used to improve the batched FHEW/TFHE bootstrapping construction introduced by Liu and Wang (Asiacrypt 2023). Our optimization provides a speed-up of 6x in latency and 3x in throughput for batched binary gate bootstrapping and a plaintext-space-dependent speed-up for batched functional bootstrapping with plaintext space smaller than $\mathbb{Z}_{512}$.
Tairong Huang, Shihe Ma, Anyu Wang, XiaoYun Wang
Trevor Yap Hong Eng, Shivam Bhasin, Léo Weissbart
Prasanna Ravi, Dirmanto Jap, Shivam Bhasin, Anupam Chattopadhyay
Breaking the Cubic Barrier: Distributed Key and Randomness Generation through Deterministic Sharding
Hanwen Feng, Zhenliang Lu, Qiang Tang
We introduce the first two DKG protocols, both achieving optimal resilience, with sub-cubic total communication and computation. The first DKG generates a secret key within an Elliptic Curve group, incurring $\widetilde{\mathcal{O}}(n^{2.5}\lambda)$ total communication and computation. The second DKG, while slightly increasing communication and computation by a factor of the statistical security parameter, generates a secret key as a field element. This property makes it directly compatible with various off-the-shelf DLog-based threshold cryptographic systems. Additionally, both DKG protocols straightforwardly imply an improved (single-shot) common coin protocol.
At the core of our techniques, we develop a simple-yet-effective methodology via deterministic sharding that arbitrarily groups nodes into shards; and a new primitive called consortium-dealer secret sharing, to enable a shard of nodes to securely contribute a secret to the whole population only at the cost of one-dealer. We also formalize simulation-based security for publicly verifiable secret sharing (PVSS), making it possible for a modular analysis for DKG. Those might be of independent interest.
Trevor Yap, Dirmanto Jap
Hao Guo, Jintai Ding
Brent Waters, David J. Wu
Shihe Ma, Tairong Huang, Anyu Wang, Xiaoyun Wang
Chun Guo, Xiao Wang, Kang Yang, Yu Yu
05 February 2024
Copenhagen, Denmark, 19 August - 22 August 2024
Submission deadline: 15 March 2024
Notification: 20 May 2024
London, United Kingdom, 2 September - 4 September 2024
Submission deadline: 3 May 2024
Notification: 5 June 2024