IACR News
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16 June 2022
Gilad Asharov, Ran Cohen, Oren Shochat
ePrint ReportOur main question is whether an alternative efficient transformation from static to adaptive security exists. We show an inherent difficulty in achieving this goal generically. In contrast to the folklore, we present a protocol that is perfectly secure with efficient static simulation (therefore also adaptively secure with inefficient simulation), but for which efficient adaptive simulation does not exist (assuming the existence of one-way permutations).
In addition, we prove that the seminal protocol of Ben-Or, Goldwasser, and Wigderson (STOC'88) is secure against adaptive, semi-honest corruptions with efficient simulation. Previously, adaptive security of the protocol, as is, was only known either for a restricted class of circuits or for all circuits but with inefficient simulation.
15 June 2022
Craig Gentry, Shai Halevi, Vinod Vaikuntanathan
ePrint ReportFirst, we observe that "bootstrapping" techniques can be used to convert any (1-hop) homomorphic encryption scheme into an $i$-hop scheme for any~$i$, and the result inherits the function-privacy and/or compactness of the underlying scheme. However, if the underlying scheme is not compact (such as schemes derived from Yao circuits) then the complexity of the resulting $i$-hop scheme can be as high as $k^{O(i)}$.
We then describe a specific DDH-based multi-hop homomorphic encryption scheme that does not suffer from this exponential blowup. Although not compact, this scheme has complexity linear in the size of the composed function, independently of the number of hops. The main technical ingredient in this solution is a \emph{re-randomizable} variant of the Yao circuits. Namely, given a garbled circuit, anyone can re-garble it in such a way that even the party that generated the original garbled circuit cannot recognize it. This construction may be of independent interest.
SortingHat: Efficient Private Decision Tree Evaluation via Homomorphic Encryption and Transciphering
Kelong Cong, Debajyoti Das, Jeongeun Park, Hilder V. L. Pereira
ePrint ReportMatteo Campanelli, Mathias Hall-Andersen
ePrint ReportDanyang Zhu, Jing Tian, Minghao Li, Zhongfeng Wang
ePrint ReportNicolas David, María Naya-Plasencia, André Schrottenloher
ePrint ReportPatrick Derbez, Baptiste Lambin
ePrint ReportAkram Khalesi, Zahra Ahmadian
ePrint Report14 June 2022
Carmit Hazay, Anasuya Acharya, Vladimir Kolesnikov, Manoj Prabhakaran
ePrint ReportWe propose a modification to the YOSO model that preserves resilience to adaptive server corruption, but allows for much more efficient protocols. In SCALES (Small Clients And Larger Ephemeral Servers) only the servers facilitating the MPC computation are ephemeral (unpredictably selected and ``speak once''). Input providers (clients) publish problem instances and collect the output, but do not otherwise participate in computation. SCALES offers attractive features, and improves over YOSO protocols in outsourcing MPC to a large pool of servers under adaptive corruption.
We build SCALES from rerandomizable garbling schemes, which is a contribution of independent interest, with additional applications.
Yanxue Jia, Shi-Feng Sun, Hong-Sheng Zhou, Dawu Gu
ePrint ReportIn this work, to enable a better understanding of the security for PSU, we provide a systematic treatment of the typical PSU protocols, which may shed light on the design of practical and secure PSU protocols in the future. More specifically, we define different versions of PSU functionalities to properly capture the subtle security issues arising from protocols following the ``split-execute-assemble'' paradigm and using Oblivious Transfer as subroutines. Then, we survey the typical PSU protocols, and categorize these protocols into three design frameworks, and prove what PSU functionality the protocols under each framework can achieve at best, in the semi-honest setting.
Subhadeep Banik
ePrint ReportMarius A. Aardal, Diego F. Aranha
ePrint ReportMore Inputs Makes Difference: Implementations of Linear Layers Using Gates with More Than Two Inputs
Qun Liu, Weijia Wang, Ling Sun, Yanhong Fan, Lixuan Wu, Meiqin Wang
ePrint ReportWe improve the previous implementations of linear layers for many block ciphers according to the area with these search algorithms. For example, we achieve a better implementation with 4-input xor gates for AES MixColumns, which only requires 243 GE in the STM 130 nm library, while the previous public result is 258.9 GE. Besides, we obtain better implementations for all 5500 lightweight matrices proposed by Li et al. at FSE 2019, and the area for them is decreased by about 21% on average.
Gennaro Avitabile, Vincenzo Botta, Daniele Friolo, Ivan Visconti
ePrint ReportThe main contribution of our work is an efficient and modular transformation that starting from a large class of $\Sigma$-protocols and a corresponding threshold relation $\mathcal{R}_\mathsf{k,\ell}$, provides an efficient $\Sigma$-protocol for $\mathcal{R}_\mathsf{k,\ell}$ with improved communication complexity w.r.t. prior results. Moreover, our transformation preserves statistical/perfect honest-verifier zero knowledge.
Throwing Boomerangs into Feistel Structures: Application to CLEFIA, WARP, LBlock, LBlock-s and TWINE
Hosein Hadipour, Marcel Nageler, Maria Eichlseder
ePrint ReportZhimei Sui, Joseph K. Liu, Jiangshan Yu, Xianrui Qin
ePrint ReportDavid Mestel, Johannes Mueller, Pascal Reisert
ePrint ReportDespite their popularity, it is commonly believed that replay attacks are inefficient but the actual threat that they pose to vote privacy has never been studied formally. Therefore, in this paper, we precisely analyze for the first time how efficient replay attacks really are.
We study this question from commonly used and complementary perspectives on vote privacy, showing as an independent contribution that a simple extension of a popular game-based privacy definition corresponds to a strong entropy-based notion.
Our results demonstrate that replay attacks can be devastating for a voter's privacy even when an adversary's resources are very limited. We illustrate our formal findings by applying them to a number of real-world elections, showing that a modest number of replays can result in significant privacy loss. Overall, our work reveals that, contrary to a common belief, replay attacks can be very efficient and must therefore be considered a serious threat.
Samed Düzlü, Juliane Krämer
ePrint ReportVincent Cheval, Charlie Jacomme, Steve Kremer, Robert Künnemann
ePrint Report13 June 2022
Technology Innovation Institute (TII) - Abu Dhabi, UAE
Job PostingTechnology Innovation Institute (TII) is a publicly funded research institute, based in Abu Dhabi, United Arab Emirates. It is home to a diverse community of leading scientists, engineers, mathematicians, and researchers from across the globe, transforming problems and roadblocks into pioneering research and technology prototypes that help move society ahead.
Cryptography Research Centre
In our connected digital world, secure and reliable cryptography is the foundation of digital information security and data integrity. We address the world’s most pressing cryptographic questions. Our work covers post-quantum cryptography, lightweight cryptography, cloud encryption schemes, secure protocols, quantum cryptographic technologies and cryptanalysis.
Position: Cryptography / Cybersecurity Engineer
Skills required for the job
Qualifications
Closing date for applications:
Contact:
Mehdi Messaoudi - Talent Acquisition Manager
Email: mehdi.messaoudi@tii.ae
More information: https://www.tii.ae/cryptography