The RIPEMD (RACE Integrity Primitives Evaluation Message Digest) hash family is a series of cryptographic hash functions known for their resilience against collision and pre-image attacks. Developed by Hans Dobbertin, Antoon Bosselaers, and Bart Preneel in 1996, these hash functions were designed as an improvement over the earlier MD4 and MD5 algorithms. A fifth variant, the original RIPEMD from 1992 is omitted here. It is essential to note that RIPEMD-128 and the original RIPEMD are not considered secure.
The revised paper (1996) by Hans Dobbertin, Antoon Bosselaers, and Bart Preneel can be found at https://link.springer.com/chapter/10.1007/3-540-60865-6_44.