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28 June 2024
Ghada Almashaqbeh, Sixia Chen, Alexander Russell
In this paper, we study this problem under two settings that model collateralized layer-two protocols. The first is a general model in which a party has an on-chain collateral $C$ with a policy to decide on whether to settle or discard each incoming transaction. The policy also specifies when to replenish $C$ based on the remaining collateral value. The second model considers a discrete setup in which $C$ is divided among $k$ wallets, each of which is of size $C/k$, such that when a wallet is full, and so cannot settle any incoming transactions, it will be replenished. We devise several online policies for these models, and show how competitive they are compared to optimal (offline) policies that have full knowledge of the incoming transaction stream. To the best of our knowledge, we are the first to study and formulate online competitive policies for collateral and wallet management in the blockchain setting.
Nicholas Michel, Mohamed E. Najd, Ghada Almashaqbeh
Zahra Motaqy, Mohamed E. Najd, Ghada Almashaqbeh
To bridge this gap, we propose chainBoost, a secure performance booster for decentralized resource markets. It expedites service related operations, reduces the blockchain size, and supports flexible service-payment exchange modalities at low overhead. At its core, chainBoost employs a sidechain, that has a (security and semantic) mutual-dependence with the mainchain, to which the system offloads heavy/frequent operations. To enable it, we develop a novel sidechain architecture composed of temporary and permanent blocks, a block suppression mechanism to prune the sidechain, a syncing protocol to permit arbitrary data exchange between the two chains, and an autorecovery protocol to support robustness and resilience. We analyze the security of chainBoost, and implement a proof-of-concept prototype for a distributed file storage market as a use case. For a market handling around 2000 transactions per round, our experiments show up to 11x improvement in throughput and 94% reduction in confirmation time. They also show that chainBoost can reduce the main blockchain size by about 90%, and that it outperforms comparable optimistic rollup solutions by reducing transaction finality by 99.7%.
Archisman Ghosh, Md. Abdur Rahman, Debayan Das, Santosh Ghosh, Shreyas Sen
Alan Li, Qingkai Liang, Mo Dong
While such transformed models seem inherently ZK-friendly, directly applying existing ZK proof frameworks still lead to suboptimal inference proving performance. To make ZKML truly practical, a quantization-and-pruning-aware ZKML framework is needed. In this paper, we propose SpaGKR, a novel sparsity-aware ZKML framework that is proven to surpass capabilities of existing ZKML methods. SpaGKR is a general framework that is widely applicable to any computation structure where sparsity arises. It is designed to be modular - all existing GKR-based ZKML frameworks can be seamlessly integrated with it to get remarkable compounding performance enhancements. We tailor SpaGKR specifically to the most commonly-used neural network structure - the linear layer, and propose the SpaGKR-LS protocol that achieves asymptotically optimal prover time. Notably, when applying SpaGKR-LS to a special series of simplified model - ternary network, it achieves further efficiency gains by additionally leveraging the low-bit nature of model parameters.
Senegue Gomez Nyamsi, Laurian Guimagang Azebaze, Emmanuel Fouotsa
Rui Gao, Zhiguo Wan, Yuncong Hu, Huaqun Wang
Mingfei Yu, Giovanni De Micheli
Jung Hee Cheon, Hyeongmin Choe, Minsik Kang, Jaehyung Kim
In this paper, we solve this implementation-side issue algorithmically by introducing \emph{Grafting}, a ciphertext modulus management system. In Grafting, we mitigate the link between the ciphertext modulus and the application-dependent scale factor. We efficiently enable rescaling by an arbitrary amount of bits by suggesting a method managing the ciphertext modulus with mostly word-sized factors. Thus, we can fully utilize the machine architecture with word-sized factors of the ciphertext modulus while keeping the application-dependent scale factors. This also leads to hardware-friendly RNS-CKKS implementation as a side effect. Furthermore, we apply our technique to Tuple-CKKS multiplication (CCS 2023), solving a restriction due to small scale factors.
Our proof-of-concept implementation shows that the overall complexity of RNS-CKKS is almost proportional to the number of coprime factors comprising the ciphertext modulus, of size smaller than the machine's word size. This results in a substantial speed-up from Grafting: $17$-$51$% faster homomorphic multiplications and $43$% faster CoeffsToSlots in bootstrapping, implemented based on the HEaaN library. We estimate that the computational gain could range up to $1.71\times$ speed-up for the current parameters used in the RNS-CKKS libraries.
26 June 2024
Pontificia Universidad Católica de Chile, Santiago, Chile
Admission to UC | Chile is highly competitive and we consistently admit the top students in the country. Among computer science students, there is a growing interest in computer security and privacy, with multiple student-led activities such as talks, seminars, cybersecurity training workshops, and tournaments.
The successful candidates will be expected to:
Applicants must:
Closing date for applications:
Contact: Applicants should submit the documents requested in https://www.ing.uc.cl/en/trabaja-con-nosotros/areas-to-apply-2/ to vacantes-academicas@ing.puc.cl (please indicate "Faculty Position in Computer Security and Privacy" in the email subject line)
More information: https://www.ing.uc.cl/en/trabaja-con-nosotros/areas-to-apply-2/
24 June 2024
University of Luxembourg
- Applied or symmetric cryptography
- Blockchain cryptography, cryptoeconomics
- Anonymity and privacy on the Internet
- Conduct, publish and present research results at conferences
- Collaborate with the two Ph.D. students of the project
- Attract funding in cooperation with academic and industrial partners
Closing date for applications:
Contact: http://emea3.mrted.ly/3p6l5
More information: https://cryptolux.org/index.php/Vacancies
Bosch Research, Renningen, Germany
Thus, we are looking for a highly motivated PhD candidate with a strong background in applied cryptography and preferably also MPC. The candidates should meet the following requirements:
- Education: Hold an M.Sc. degree (or equivalent) with excellent grades in IT security or computer science.
- Experience and Knowledge: Strong background in (applied) cryptography with a particular focus on cryptographic protocols/MPC, including security models and basic security proof techniques. Good software development/programming skills.
- Personality and Working Practice: Self-motivated and enthusiastic, independent, reliable, creative, and able to work in an international team with diverse background.
- Language: Fluent English language skills.
If the above requirements apply to you, you are welcome to read on. The successful candidate will:
- become a part of the team and advance research on MPC.
- develop novel approaches to improve the practical efficiency of actively secure MPC protocols.
- design efficient MPC protocols for diverse use-cases.
- publish and present the results in top-tier journals and at conferences.
Please submit your application, including your CV, transcripts of records from your Master studies, and a cover letter including your research background and research interest, via: https://smrtr.io/hmG3C
Closing date for applications:
Contact: Formal applications must be submitted through: https://smrtr.io/hmG3C
Monash University
Closing date for applications:
Contact: Rafael Dowsley
Aydin Abadi
Aydin Abadi, Yvo Desmedt
Chaya Ganesh, Shreyas Gupta, Bhavana Kanukurthi, Girisha Shankar
We show that for rational and computationally bounded parties participating in our second-price auctions protocol, there exists a privacy-preserving dominant strategy equilibrium in which every party prefers to follow the protocol rather than to deviate.
Our protocol is implemented using open-source cryptographic constructs. Running our SPA protocol on commodity hardware with $15$ bidders, with bids of length $10$ bits, completes in $1.26$sec and has total communication of $0.77$MB whereas, under similar conditions, Atlas (semi-honest) protocol takes $40\%$ more time ($2.11$ sec) and $87\%$ more communication ($6.09$MB).
Peng Yang, Zoe Lin Jiang, Jiehang Zhuang, Junbin Fang, Siu Ming Yiu, Xuan Wang
To address the above issues, we propose a secure BNN inference framework, FSSiBNN, with free bitwidth conversion based on function secret sharing (FSS). Specifically, by leveraging the property of FSS that supports arbitrary input and output bitwidths, we propose a bitwidth conversion embedding scheme. We naturally embed the bitwidth conversion into the FSS-based secure activation and max pooling computation, thereby avoiding the additional computational and communication overhead introduced by the bitwidth conversion. Moreover, we combine and convert multiple BNN layer functions into fewer matrix multiplication and comparison operations, and precompute multiplication tuples and FSS keys in the offline phase to achieve constant-round online inference.
In the experiment, we conduct tests on various datasets and models, and compare our results with state-of-the-art work. Compared to the existing best two-party framework XONN (USENIX Security '19), our work is approximately 7$\times$ faster in inference time and reduces communication overhead by about 577$\times$. Compared with the existing best three-party frameworks, SecureBiNN (ESORICS '22) and FLEXBNN (TIFS '23), our work is approximately 2.5$\times$ faster in inference time and reduces communication overhead by 1.3 to 16.4$\times$.
Maciej Obremski, João Ribeiro, Lawrence Roy, François-Xavier Standaert, Daniele Venturi
In this work, we study noisy leakage models stemming from hockey-stick divergences, which generalize statistical distance and are also the basis of differential privacy. First, we show that resilience to bounded leakage and random probing implies resilience to our new noisy leakage model with improved parameters compared to models based on the statistical distance or mutual information. Second, we establish composition theorems for our model, showing that these connections extend to a setting where multiple leakages are obtained from a leaking implementation. We complement our theoretical results with a discussion of practical relevance, highlighting that (i) the reduction to bounded leakage applies to realistic leakage functions with noise levels that are decreased by several orders of magnitude compared to Brian et al., and (ii) the reduction to random probing usefully generalizes the seminal work of Duc, Dziembowski, and Faust, although it remains limited when the field size in which masking operates grows (i.e., hockey-stick divergences can better hide the field size dependency of the noise requirements, but do not annihilate it).
Xichao Hu, Dengguo Feng, Lin Jiao, Yonglin Hao, Xinxin Gong, Yongqiang Li
Theoretically, we propose 5 IBD constructions aligned with the techniques of arbitrary S-box, boomerang distinguisher, Boomerang Connectivity Table, U/L/EBCT and mixed tables for differential propagation for SPN-network block ciphers, and 2 IBD constructions accompanied by state propagation for block ciphers with any structure. Furthermore, we investigate the relationship among these IBD constructions and demonstrate that the most superior IBD aligns precisely with the original definition. Technically, we develop a general SAT-based automatic search tool for IBDs by introducing optimized search strategies of the composite model method and the mixed model method. This tool not only considers the details of each operation but also takes into account the impact of key schedule in a single-key setting.
As applications, we first acquire 59584 4-round 1 active word truncated IBDs for AES-128, and 192 of those IBDs cannot be detected by the $\mathcal{UB} \text{-method}$. For Midori64, we first demonstrate the non-existence of $7$-round $1$ active word truncated IBDs, and obtain $7296$ $6$-round $1$ active word truncated IBDs, which is complementary to the finding that there are no existing $6$-round $1$ active word truncated IDs. For PRESENT-80, we get the first 6-round IBDs which cannot be detected by the $\mathcal{UB}\text{-method}$. Those results indicate that our method outperforms the $\mathcal{UB}\text{-method}$ and offer an advantage over IDs. We believe that our work can bring new insights to symmetric cipher analysis.