We congratulate Xiaoen Lin, Hongbo Yu, Enming Dong, Wenhao Wu and Yantian Shen of Tsinghua University and of The National Research Center of Parallel Computer Engineering and Technology, Beijing, China, for solving the 5-round pre-image challenge on Keccak[r=640, c=160].

It is the first time that a 5-round pre-image challenge of our crunchy contest is solved! The solution to the present challenge spans 27 blocks and was obtained using internal differential cryptanalysis involving symmetric states. The team reports a total complexity of about 2⁶¹ 5-round Keccak-f calls. The experiment was completed in around 7 days using 3000 core-groups on the new Sunway supercomputer! More details can be found in the slides that Xiaoen presented at PBC 2025.