High Quality Content by WIKIPEDIA articles! In cryptography, COCONUT98 (Cipher Organized with Cute Operations and N-Universal Transformation) is a block cipher designed by Serge Vaudenay in 1998. It was one of the first concrete applications of Vaudenay`s decorrelation theory, designed to be provably secure against differential cryptanalysis, linear cryptanalysis, and even certain types of undiscovered cryptanalytic attacks.