Layer 2 is one of the most promising approaches to improve the scalability of blockchains. The idea is to shift some tasks (e.g., ordering and execution of some transactions) off the mainchain (i.e., layer 1) to reduce the workload of the mainchain. In this work, we study the so-called committee-based layer 2 approaches. Being conceptually similar to sharding, committee-based layer 2 approaches allow committees to order and execute transactions in parallel to further improve the performance of the system. Different from existing committee-based layer 2 solutions that often prioritize low latency over high throughput, our solution strives to achieve both low latency and high throughput. The technical building blocks include a lightweight primary-backup design for off-chain committees, an efficient on-chain lease management design for managing the primaries, and a one-phase solution for cross-committee transactions (i.e., transactions that need to be processed by multiple committees). Experimental results show that our solution achieves both low latency and high throughput and can be deployed on even low-end machines.

Abstract GIFT is a lightweight cipher proposed by Banik et al. at CHES’17, motivated by the design strategy of PRESENT. GIFT-64[2021] is a variant of GIFT proposed by Sun et al. at EUROCRYPT’22 to achieve better resistance against differential attack while maintaining a similar security level against linear attack. At EUROCRYPT’22, Dong et al. proposed a new rectangle framework considering the key guessing strategies for linear key-schedule ciphers, and established a uniform automatic search model for the whole rectangle attack. In this paper, we extend it to be applicable to bit-oriented ciphers, and construct an automatic search model involved in the distinguisher and key-recovery phase for GIFT. Moreover, we utilize the key relations of the linear key-schedule to the model, and find some new distinguishers both for GIFT-64 and GIFT-64[2021]. To evaluate the probability more accurately, we propose a method to calculate the probability of the 2-round middle part which connects the boomerang distinguisher for GIFT, and apply it with the SAT method to evaluate the probability of the whole distinguishers. As a result, we search out a new 20-round related-key boomerang distinguisher for GIFT-64, and achieve a 26-round attack with better time complexity than the best previous attack. For GIFT-64[2021], we find a 20-round boomerang distinguisher and give the first 26-round rectangle attack under related-key scenario.

Abstract We introduce an interpolation attack using the Moebius Transform. This can reduce the time complexity to get a linear system of equations for specified intermediate state bits, which is general to cryptanalysis of some ciphers with update function of low algebraic degree. Along this line, we perform an interpolation attack against Elephant-Delirium, a round 2 submission of the ongoing national institute of standards and technology (NIST) lightweight cryptography project. This is the first third-party cryptanalysis on this cipher. Moreover, we promote the interpolation attack by applying it to the Farfalle pseudo-random constructions Kravatte and Xoofff. Our attacks turn out to be the most efficient method for these ciphers thus far.

Abstract A new conditional cube attack was proposed by Li et al. at ToSC 2019 for cryptanalysis of Keccak keyed modes. In this paper, we find a new property of Li et al.’s method. The conditional cube attack is modified and applied to cryptanalysis of 5-round Ketje Jr, 6-round Xoodoo-AE and Xoodyak, where Ketje Jr is among the third round CAESAR competition candidates and Xoodyak is a Round 2 submission of the ongoing NIST lightweight cryptography project. For the updated conditional cube attack, all our results are shown to be of practical time complexity with negligible memory cost, and test codes are provided. Notably, our results on Xoodyak represent the first third-party cryptanalysis for Xoodyak.