Started in June 2011, the Crunchy Contest proposes concrete collision and pre-images challenges based on reduced-round Keccak. After about 13 years, it is still active and the recent months have seen new challenges being solved. Hence, we would like to congratulate the authors of the latest solutions:

• We congratulate Xiaoen Lin¹, Hongbo Yu¹, Zhengrong Lu¹ and Yantian Shen¹ for solving the 2-round pre-image challenge on Keccak[r=40, c=160].

  The previous pre-image challenge on the 200-bit version was solved on 1 round by Joan Boyar and Rene Peralta in 2013. This present challenge was solved by combining linear structures and symmetries within the lanes and exploiting sparsity of the round constants.

• Furthermore, we congratulate Xiaoen Lin¹, Hongbo Yu¹, Congming Wei², Le He³ and Chongxu Ren¹ for solving the 4-round pre-image challenge on Keccak[r=640, c=160].

  The previous pre-image challenge on the 800-bit version was solved on 3 rounds by Jian Guo and Meicheng Liu in 2017. The solution to the present challenge was made possible by a number of optimizations related to linear structures and made use of mixed-integer linear programming (MILP). The team reports a total complexity of 2^60.9 4-round Keccak-f calls.

• Finally, we congratulate Andreas Westfeld⁴ for solving the 2-round collision challenge on Keccak[r=40, c=160].

  The previous collision challenge on the 200-bit version was solved on 1 round by Roman Walch and Maria Eichlseder in September 2017. The solution to the present challenge targets the rounds 3 and 4 specifically, as it exploits the round constant that is zero for i_r=3 in the 200-bit version.

1. Department of Computer Science and Technology, Tsinghua University, Beijing, China
2. Beijing Institute of Technology, Beijing, China
3. School of Cyber Engineering, Xidian University, Xi'an, China
4. Faculty of Informatics/Mathematics, HTW Dresden, Germany