This paper uses new types of local collisions named
one-message-word local collisions
to construct meet-in-the-middle preimage attacks on two double-branch hash functions RIPEMD and RIPEMD-128, and obtains the following results.
A pseudo-preimage and second preimage attacks on the first 47 steps of RIPEMD (full version: 48 steps) are proposed with complexities of 2
compression function computations, respectively. The number of the attacked steps is greatly increased from previous preimage attacks on the first 33 steps and intermediate 35 steps.
A pseudo-preimage and preimage attacks on intermediate 36 steps of RIPEMD-128 (full version: 64 steps) are proposed with complexities of 2
compression function computations, respectively, while previous attacks can work at most intermediate 35 steps.