Bart Preneel
Belgian cryptographer at KU Leuven whose name is on RIPEMD-160, Miyaguchi–Preneel and about half of Europe's cryptography projects.
Preneel's 1993 PhD thesis mapped out how to build hash functions from block ciphers, and the Miyaguchi–Preneel construction is one of the few that holds up. In 1996, with Hans Dobbertin and Antoon Bosselaers, he released RIPEMD-160, a European counterweight to SHA-1 that later ended up in Bitcoin's address format.
He coordinated NESSIE (2000–2003), the EU's open competition for cryptographic primitives, and the ECRYPT network, whose stream cipher contest produced Trivium — which he co-designed. He led the COSIC group in Leuven, the same environment that produced the AES designers, and was president of the IACR from 2008 to 2013. Belgium is a small country with an unreasonable amount of cryptography.