On the Indifferentiability of Fugue and Luffa

Rishiraj Bhattacharyya, Avradip Mandal

Abstract: Indifferentiability is currently considered to be an important security notion for a cryptographic hash function to instantiate Random Oracles in different security proofs. In this paper, we prove indifferentiability of Fugue and Luffa, two SHA3 second round candidates. We also analyze the indifferentiability of a modified Luffa mode replacing multiple small permutations by a single large permutation.