Bart Preneel (born 15 October 1963) is a Flemish cryptographer and cryptanalyst.
He is a professor at Katholieke Universiteit Leuven, in the COSIC group,.
He was the president of the International Association for Cryptologic Research in 2008-2013 and project manager of ECRYPT.
Simultaneously with Shoji Miyaguchi, he invented the Miyaguchi–Preneel scheme, a robust structure used in hash functions such as Whirlpool.
He is one of the authors of the RIPEMD-160 hash function.
He was also a co-inventor of the stream cipher MUGI which would later become a Japanese standard, and of the stream cipher Trivium which is a well-received entrant to the eSTREAM project.
He has also contributed to the cryptanalysis of RC4, SOBER-t32, MacGuffin, Helix, Phelix, Py, TPypy, the HAVAL cryptographic hash function and the SecurID hash function, among others.