Classification and generation of disturbance vectors for collision attacks against SHA-1

The main contribution of this paper is to provide a classification of disturbance vectors used in differential collision attacks against SHA-1. We show that all published disturbance vectors can be classified into two types of vectors, type-I and type-II. We present a deterministic algorithm which produce efficient disturbance vectors with respect to any given cost function. We define two simple cost functions to evaluate the efficiency of a candidate disturbance vector. Using our algorithm and those cost function we retrieved all previously known vectors and found that the most efficient disturbance vector is the one first reported as Codeword2 by Jutla and Patthak in [7].