IACR News
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10 April 2024
Charlotte Lefevre, Bart Mennink
Leonie Reichert, Gowri R Chandran, Phillipp Schoppmann, Thomas Schneider, Björn Scheuermann
In this paper, we present Menhir, an oblivious TEE database that hides access patterns with ORAM guarantees and volume patterns through differential privacy. The database allows range and point queries with SQL-like WHERE-clauses. It builds on the state-of-the-art oblivious AVL tree construction Oblix (S&P'18), which by itself does not protect against volume leakage. We show how volume leakage can be exploited in range queries and improve the construction to mitigate this type of attack. We prove the correctness and obliviousness of Menhir. Our evaluation shows that our approach is feasible and scales well with the number of rows and columns in the database.
Yilei Chen
To develop a quantum algorithm for solving LWE, we mainly introduce two new techniques. First, we introduce Gaussian functions with complex variances in the design of quantum algorithms. In particular, we exploit the feature of the Karst wave in the discrete Fourier transform of complex Gaussian functions. Second, we use windowed quantum Fourier transform with complex Gaussian windows, which allows us to combine the information from both time and frequency domains. Using those techniques, we first convert the LWE instance into quantum states with purely imaginary Gaussian amplitudes, then convert purely imaginary Gaussian states into classical linear equations over the LWE secret and error terms, and finally solve the linear system of equations using Gaussian elimination. This gives a polynomial time quantum algorithm for solving LWE.
Alexander Hoover, Ruth Ng, Daren Khu, Yao'an Li, Joelle Lim, Derrick Ng, Jed Lim, Yiyang Song
We address this by providing the first leakage-abuse attacks against StE for SQL schemes. Our attacks can be run by a passive adversary on a server with access to some information about the distribution of underlying data, a common model in prior work. They achieve partial query recovery against select operations and partial plaintext recovery against join operations. We prove the optimality and near-optimality of two new attacks, in a Bayesian inference framework. We complement our theoretical results with an empirical investigation testing the performance of our attacks against real-world data and show they can successfully recover a substantial proportion of queries and plaintexts.
In addition to our new attacks, we provide proofs showing that the conditional optimality of a previously proposed leakage-abuse attack and that inference against join operations is NP-hard in general.
Yuxi Xue, Xingye Lu, Man Ho Au, Chengru Zhang
To instantiate our framework, we adapt the well-known post-quantum secure non-interactive argument of knowledge (NIAoK), ethSTARK, into an SoK. This SoK inherents the post-quantum security and has a signature size poly-logarithmic in the size of the NP statement. Thus, our resulting LRS has a signature size of $O(\text{polylog}(\log n))$. By comparison, existing post-quantum ring signatures, regardless of linkability considerations, have signature sizes of $O(\log n)$ at best. Furthermore, leveraging online/offline verification, part of the verification of signatures on the same ring can be shared, resulting in a state-of-the-art amortized verification cost of $O(\text{polylog}(\log n))$.
Our LRS also performs favourably against existing schemes in practical scenarios. Concretely, our scheme has the smallest signature size among all post-quantum ring signatures for any ring size larger than $32$. In our experiment, at $128$-bit security and ring size of $1024$, our LRS has a size of $29$KB, and an amortized verification cost of $0.3$ ms, surpassing the state-of-the-art by a significant margin. Even without considering amortization, the verification time for a single signature is $128$ ms, which is still 10x better than state-of-the-art succinct construction, marking it comparable to those featuring linear signature size. A similar performance advantage can also be seen at signing.
Mario Yaksetig
Our findings indicate that most challenges can be effectively addressed through the implementation of cryptography and subnets (i.e., Avalanche architecture), which allow for segmented, optimized environments within the broader metaverse ecosystem. This approach not only enhances performance but also provides a flexible framework for managing the diverse needs of metaverse applications.
Nimish Mishra, Debdeep Mukhopadhyay
Mustafa Khairallah
In this paper, we present two new AEAD modes and four instantiations based on Tweakable Block Ciphers. These new modes target equipping high-speed applications on parallel platforms with nonce misuse resistant AEAD (MRAE). The first mode, LLSIV, targets similar performance on single-core platforms to SCT-2, while eliminating the bottlenecks that make SCT-2 not fully parallelizable. The enhanced parallelism allows LLSIV to encrypt significantly more blocks on parallel platforms, compared to SCT-2, in the same amount of time. LLSIV is based on the NaT MAC, where each ciphertext block can itself be viewed as an instance of NaT when the plaintext is prepended with $0^n$. The trade-off is that LLSIV requires the inverse function of the TBC. However, the inverse function is used only once per message and we demonstrate that for parallel implementations it represents a very small overhead.
We give an instantiation of LLSIV based on the SKINNY-128-384 TBC, and a pruned scheme, dubbed pLLSIV, which targets enhanced performance compared both SCT-2 and LLSIV on all platforms, while having reduced security claims. It relies on the recently popularized prove-then-prune methodology to take full advantage of the properties of LLSIV. This leads to a significant performance improvement, making pLLSIV even faster than online TBC-based schemes that are not MRAE-secure. Last but not least, we give an instantiation that uses the primitives used in AES-GCM-SIV: the PolyVal hash function and AES. Our instantiation is faster than AES-GCM-SIV on all platforms and have better bounds. On the other hand, it relies on the ideal cipher model as it uses the ICE TBC proposed as part of the Remus AEAD design.
The second mode we describe is LLDFV. It uses ideas from LLSIV combined the Decryption-Fast SIV (DFV) framework proposed recently by Minematsu. The goal is to reduce the number of calls to the TBC by one, while making the scheme as parallelizable as LLSIV. This makes the scheme faster that DFV on all platforms.
Zeyu Xu, Jiamin Cui, Kai Hu, Meiqin Wang
Décio Luiz Gazzoni Filho, Tomás S. R. Silva, Julio López
Stanislav Peceny, Srinivasan Raghuraman, Peter Rindal, Harshal Shah
We give two novel protocols for efficiently generating a random permutation correlation. The first makes use of recent advances in MPC-friendly PRFs to obtain a protocol requiring $O(n\ell)$ OTs/time and constant rounds to permute $n$ $\ell$-bit strings. Unlike the modern OT extension techniques we rely on, this was previously only achievable from relatively more expensive public-key cryptography, e.g. Paillier or LWE. We implement this protocol and demonstrate that it can generate a correlation for $n=2^{20},\ell=128$ in 19 seconds and $\sim2\ell n$ communication, a 15 \& $1.1\times$ improvement over the LWE solution of Juvekar at al. (CCS 2018). The second protocol is based on pseudo-random correlation generators and achieves an overhead that is \emph{sublinear} in the string length $\ell$, i.e. the communication and number of OTs is $O(n\log \ell)$. The latter protocol is ideal for the setting when you need to repeatedly permute secret-shared data by the same permutation, e.g. in graph algorithms.
Finally, we present a suite of highly efficient protocols for performing various batched random access operations. These include a class of protocols we refer to as \emph{extraction}, which allow a user to \emph{mark} a subset of $X$ and have this subset obliviously extracted into an output list. Additionally, the parties can specify an \emph{arbitrary} selection function $\sigma:[n]\rightarrow[n]$ and obtain shares of $\sigma(X)=(X_{\sigma(1)},\ldots,X_{\sigma(n)})$ from $X$. We implement these protocols and report on their performance.
Martin R. Albrecht, Matilda Backendal, Daniele Coppola, Kenneth G. Paterson
We provide the first detailed documentation and security analysis of Nextcloud's E2EE feature. Nextcloud's strong security claims motivate conducting the analysis in the setting where the server itself is considered malicious. We present three distinct attacks against the E2EE security guarantees in this setting. Each one enables the confidentiality and integrity of all user files to be compromised. All three attacks are fully practical and we have built proof-of-concept implementations for each. The vulnerabilities make it trivial for a malicious Nextcloud server to access and manipulate users' data.
We have responsibly disclosed the three vulnerabilities to Nextcloud. The second and third vulnerabilities have been remediated. The first was addressed by temporarily disabling file sharing from the E2EE feature until a redesign of the feature can be made. We reflect on broader lessons that can be learned for designers of E2EE systems.
09 April 2024
Paris, France, 26 June 2024
Submission deadline: 5 May 2024
Notification: 12 May 2024
Arlington, USA, 23 October - 25 October 2024
Submission deadline: 6 June 2024
Notification: 30 July 2024
Halifax, Canada, 4 September 2024
Brandenburg University of Technology, Chair of IT Security
- Privacy-Enhancing Technologies in Cyber-Physical Systems.
- AI-based Network Attack Detection and Simulation.
- AI-enabled Penetration Testing.
Closing date for applications:
Contact: Ivan Pryvalov (ivan.pryvalov@b-tu.de)
Graz University of Technology
Join our Cryptographic Engineering research team at the Technical University of Graz (TU Graz) in Austria! We are seeking a one PhD and one postdoctoral researchers.
You will contribute to an exciting research project advancing isogeny-based cryptography. This role offers a unique opportunity to collaborate with leading experts in the field and perform cutting-edge research.
The Cryptographic Engineering research team is based at IAIK, TU Graz, the largest university institute in Austria for research and education in security and privacy. It has been active in this field for more than 30 years and currently employs more than 60 researchers.
Required Qualifications for PhD position:The ideal candidate for the PhD position will hold a master's degree with project experience in the implementation aspects (e.g., efficient implementation, side-channel analysis, fault analysis, etc.) of cryptography, preferably in isogeny-based cryptography.
Required Qualifications for Postdoc position:The ideal candidate for the postdoc position will hold a PhD (or be close to completion) in cryptography and be an expert in isogeny-based cryptography and/or secure implementation aspects of cryptography.
How to apply:
Submit your applications, CV, and other documents before 1st May, 2024.
https://jobs.tugraz.at/en/jobs/bbba0417-7a9c-69a5-f012-6613bd4b383f/apply?preview=true
Closing date for applications: The application deadline is May 1st, 2024.
Closing date for applications:
Contact: Sujoy Sinha Roy – sujoy.sinharoy@iaik.tugraz.at
Vu Amsterdam
Closing date for applications:
Contact: Kristina Sojakova
More information: https://workingat.vu.nl/vacancies/phd-in-effective-and-scalable-tools-against-side-channel-attacks-amsterdam-1064918
Quantstamp
Quantstamp is looking for an applied cryptographer. Quantstamp often deals with a wide range of cryptographic problems, including reviewing implementations and tackling new theoretical problems using cryptography. For example, Quantstamp regularly receives requests to review code bases which either invoke or implement (custom) cryptography, as part of an audit.
Requirments
Closing date for applications:
Contact: candidate-upload-to-job-N7wnRj36Krf2zX@inbox.ashbyhq.com
More information: https://jobs.ashbyhq.com/quantstamp/6ae4fc70-98bb-42e1-9f24-c40e7af441cc
Monash University; Melbourne, Australia
- highly competitive scholarships to cover tuition fees, health insurance and living expenses (as stipend),
- opportunities to collaborate with leading academic and industry experts in the related areas,
- opportunities to participate in international grant-funded projects,
- collaborative and friendly research environment,
- an opportunity to live/study in one of the most liveable and safest cities in the world.
Requirements. A strong mathematical and cryptography background is required. Some knowledge/experience in coding (for example, Python, C/C++, SageMath) is a plus. Candidates must have completed (or be about to complete within the next 8 months) a significant research component either as part of their undergraduate (honours) degree or masters degree. They should have excellent English verbal and written communication skills.
How to apply. please first refer to mfesgin.github.io/supervision/ for more information. Then, please fill out the following form (also clickable from the advertisement title): https://docs.google.com/forms/d/e/1FAIpQLScOvp0w397TQMTjTa6T7TKqri703Z-c3en0aS654w6nl4_EFg/viewform
Closing date for applications:
Contact: Muhammed Esgin
More information: https://docs.google.com/forms/d/e/1FAIpQLScOvp0w397TQMTjTa6T7TKqri703Z-c3en0aS654w6nl4_EFg/viewform