International Association
for Cryptologic Research

This paper combines techniques from several previous papers with some modifications to improve the previous cryptanalysis of 3-round Keccak-256. Furthermore, we propose a fast rebuilding method to improve the efficiency of solving equation systems. As a result, the guessing times of finding a preimage for 3-round Keccak-256 are decreased from $2^{65}$ to $2^{52}$, and the solving time of each guess is decreased from $2^{9}$ 3-round Keccak calls to $2^{5.3}$ 3-round Keccak calls. We identify a preimage of all '0' digest for 3-round Keccak-256 to support the effectiveness of our methodology.