Token Free Bounded Delay Codes and Hash Iteration

A hash iteration technique takes as input a hash compression function which works on fixed length binary strings and outputs a hash function which works on arbitrary length binary strings. In this paper we introduce token-free bounded delay codes and then use them to define a hash iteration technique. The newly created schema, when applied to a hash compression function, preserves the following security properties: preimage resistance (Pre), always preimage-resistance (aPre), everywhere preimage-resistance (ePre) and collision-resistance (Coll). The proofs for the preservation of the second-preimage resistance (Sec), always second-preimage resistance (aSec), and everywhere second-preimage resistance (eSec) are part of our future work. Comparisons with other iteration techniques are also provided.