IACR News
Here you can see all recent updates to the IACR webpage. These updates are also available:
23 February 2024
Dilara Toprakhisar, Svetla Nikova, Ventzislav Nikov
Jules Maire, Damien Vergnaud
Paweł Lorek, Moti Yung, Filip Zagórski
It turned out, however, that a series of works showed, however, subtle issues with analyses behind RPC. First, that the actual security level of the RPC protocol is way off the claimed bounds. The probability of successful manipulation of $k$ votes is $(\frac{3}{4})^k$ instead of the claimed $\frac{1}{2^k}$ (this difference, in turn, negatively affects actual implementations of the notion within existing election systems. This is so since concrete implemented procedures of a given length were directly based on this parameter).
Further, privacy guarantees that a constant number of mix-servers is enough turned out to also not be correct. We can conclude from the above that these analyses of the processes of mixing are not trivial.
In this paper, we review the relevant attacks, and we present Mirrored-RPC -- a fix to RPC based on ``mirrored commitment'' which makes it optimally secure; namely, having a probability of successful manipulation of $k$ votes $\frac{1}{2^k}$.
Then, we present an analysis of the privacy level of both RPC and mRPC. We show that for $n$ messages, the number of mix-servers (rounds) needed to be $\varepsilon$-close to the uniform distribution in total variation distance is lower bounded by: \[ r(n, \varepsilon) \geq \log_{2}{n \choose 2}/\varepsilon. \]
This proof of privacy, in turn, gives insights into the anonymity of various cryptocurrencies (e.g., Zerocash) using anonymizing pools. If a random fraction $q$ of $n$ existing coins is mixed (in each block), then to achieve full anonymity, the number of blocks one needs to run the protocol for, is: \[ rb(n, q, \varepsilon) \geq - \frac{\log n + \log (n-1) - \log (2\varepsilon)}{ {\log({1-q^2}})}. \]
Barış Ege, Bob Swinkels, Dilara Toprakhisar, Praveen Kumar Vadnala
Carmit Hazay, Yibin Yang
The main source of difficulty in lifting the security of garbling schemes-based protocols to the malicious setting lies in proving the correctness of the underlying garbling scheme. In this work, we analyze the security of Ball et al.'s scheme in the presence of malicious attacks.
- We demonstrate an overflow attack, which is inevitable in this computational model, even if the garbled circuit is fully correct. Our attack follows by defining an adversary, corrupting either the garbler or the evaluator, that chooses a bad input and causes the computation to overflow, thus leaking information about the honest party's input. By utilizing overflow attacks, we show that $1$-bit leakage is necessary for achieving security against a malicious garbler, discarding the possibility of achieving full malicious security in this model. We further demonstrate a wider range of overflow attacks against a malicious evaluator with more than $1$ bit of leakage.
- We boost the security level of Ball et al.'s scheme by utilizing two variants of Vector Oblivious Linear Evaluation, denoted by VOLEc and aVOLE. We present the first constant-round constant-rate 2PC protocol over bounded integer computations, in the presence of a malicious garbler with $1$-bit leakage and a semi-honest evaluator, in the {VOLEc,aVOLE}-hybrid model and being black-box in the underlying group and ring. Compared to the semi-honest variant, our protocol incurs only a constant factor overhead, both in computation and communication. The constant-round and constant-rate properties hold even in the plain model.
Antoine Joux, Hunter Kippen, Julian Loss
Polynomial Commitments from Lattices: Post-Quantum Security, Fast Verification and Transparent Setup
Valerio Cini, Giulio Malavolta, Ngoc Khanh Nguyen, Hoeteck Wee
Surprisingly, as far as plausibly quantum-safe polynomial commitments are concerned, the currently most efficient constructions only rely on weak cryptographic assumptions, such as security of hash functions. Indeed, despite making use of the underlying algebraic structure, prior lattice-based polynomial commitments still seem to be much behind the hash-based ones. Moreover, security of the aforementioned lattice constructions against quantum adversaries was never formally discussed.
In this work, we bridge the gap and propose the first (asymptotically and concretely) efficient lattice-based polynomial commitment with transparent setup and post-quantum security. Our interactive variant relies on the standard (Module-)SIS problem, and can be made non-interactive in the random oracle model using Fiat-Shamir transformation. In addition, we equip the scheme with a knowledge soundness proof against quantum adversaries which can be of independent interest. In terms of concrete efficiency, for $L=2^{20}$ our scheme yields proofs of size $2$X smaller than the hash-based \textsf{FRI} commitment (Block et al., Asiacrypt 2023), and $70$X smaller than the very recent lattice-based construction by Albrecht et al. (Eurocrypt 2024).
Renas Bacho, Julian Loss, Gilad Stern, Benedikt Wagner
In this work, we present HARTS, the first threshold Schnorr signature scheme to incorporate all these desiderata. More concretely:
- HARTS is adaptively secure and remains fully secure and operational even under asynchronous network conditions in the presence of up to $t_c < n/3$ malicious parties. This is optimal.
- HARTS outputs a Schnorr signature of size $\lambda$ with a near-optimal amortized communication cost of $O(\lambda n^2 \log{n})$ bits and $O(1)$ rounds per signature.
- HARTS is a high-threshold scheme: no fewer than $t_r+1$ signature shares can be combined to yield a full signature, where $t_r\geq 2n/3 > 2t_c$. This is optimal.
We prove our result in a modular fashion in the algebraic group model. At the core of our construction, we design a new simple, and adaptively secure high-threshold AVSS scheme which may be of independent interest.
River Moreira Ferreira, Ludovic Perret
21 February 2024
Virtual event, Anywhere on Earth, 13 August - 14 August 2024
Submission deadline: 15 April 2024
Notification: 14 June 2024
Paris, France, 9 September - 20 December 2024
Submission deadline: 15 March 2024
Indian Institute of Science Education and Research (IISER ) Pune
Closing date for applications:
Contact: math.postdocapplications@iiserpune.ac.in
More information: https://www.iiserpune.ac.in/announcements/10/postdoctoral-positions-in-mathematics
Blanqet
We are looking to hire several researchers to join our Chicago based team for periods of one to three years with the potential for longer employment. Our focus is on imaginative individuals who are devoted to both research and its practical realization. Relevant areas of interest include, but are not limited to, cryptography, quantum and post-quantum cryptography, computer security, computational algebra and number theory.
Successful candidates will have the opportunity to work alongside other researchers at Blanqet and at the nearby University of Chicago. Joint academic affiliations with the University of Chicago are possible when appropriate.
Applicants are expected to have (or expect to soon have) a Ph.D. in computer science, mathematics, physics or a related area. To apply, submit a curriculum vitae (including a list of publications), and a brief description of your research interests (description of research interests not to exceed two pages, more or less, and arrange for three letters of reference. Applications and letters should be sent via email to contact@blanqet.net. We will make offers on a rolling basis with flexibility as to the start date.
Closing date for applications:
Contact: contact@blanqet.net
Chair of IT Security, Brandenburg University of Technology, Cottbus, Germany
Our chair performs research and teaching in the area of IT Security with a strong focus on Network Security and Online Privacy. Our goal is to advance the state of the art in research and to educate qualified computer scientists in the area of IT Security who are able to meet the challenges of the growing demand on securing IT Systems and provide data protection in various areas of our life and society. More information about us can be found at https://www.b-tu.de/en/fg-it-sicherheit.
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
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 15.03.2024 at itsec-jobs.informatik@lists.b-tu.de. Applications sent to email addresses other than that will be automatically discarded.
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.informatik.tu-cottbus.de/~andriy/phd-ad-btu_en.pdf
19 February 2024
Ulrich Haböck, David Levit, Shahar Papini
Juliane Krämer, Mirjam Loiero
Jiseung Kim, Changmin Lee
We propose an improvement to the Gaussian elimination attack, which is also known as Prange's information set decoding algorithm, for solving the LPN problem. Contrary to prevailing knowledge, we find that the Gaussian elimination attack is highly competitive and currently the best method for solving LPN over large fields. Our improvement involves applying partial Gaussian elimination repeatedly, rather than the whole Gaussian algorithm, which we have named the ``Reduce and Prange's algorithm".
Moreover, we provide two applications of Reduce and Prange algorithms: One is the hybrid algorithm of ours and Berstein, Lange and Peters's algorithm at PQCrypto'08, and the other one is Reduce and Prange algorithm for LPN with regular noise.
Last, we provide a concrete estimation of the bit-security of LPN variants using our Reduce and Prange's frameworks. Our results show that the bit-security of LPN over $\mathbb{F}_q$ is reduced by 5-11 bits when $\log q = 128$ compared to previous analysis by Liu et al. (will appear at Eurocrypt'24). Furthermore, we show that our algorithm outperforms recent work by Briaud and Øygard (Eurocrypt'23) and Liu et al. for certain parameters. It reduces the bit-security of LPN with regular noise by 5-28 bits.