Abstract:RIPEMD-128 is a cryptographic hash function proposed in 1996 by Hans Dobbertin, Antoon Bosselaers and Bart Preneel. It consists of two different and independent parallel parts, with which the results in each application of the compression function. This paper presents a practical attack for finding collisions for the first 32-step reduced RIPEMD-128 with complexity of 228 32-step reduced RIPEMD-128 operations. This is the first published analysis for the first 32-step reduced RIPEMD-128.