In 2007, the U.S. National Institute of Standards and Technology (NIST) announced a public contest aiming at the selection of a new standard for a cryptographic hash function. The main motivation behind starting the contest has been the security flaws identified in the SHA-1 standard in 2005. Similarities between SHA-1 and the most recent standard SHA-2 were worrisome and NIST decided that a new, stronger hash function would be needed. In this paper, the authors attack round-reduced KECCAK hash function with a technique called rotational cryptanalysis. They focus on KECCAK variants proposed as SHA-3 candidates in the NIST's contest for a new standard of cryptographic hash function.