Using the Discrete Squaring Function in the Delayed Message Authentication Protocol

The delayed message authentication protocol (DeMA protocol) is a protocol that can be used in order to exchange authentic information between two entities by using a one-way chain (i.e. an array of elements generated by a one-way function) on each entity's side. The use of the discrete power function in the DeMA protocol offers the advantage that the length of the chains does not influence the computational time. In this paper we are concerned with the particular case of the discrete squaring function which offers more computational advantages since the elements of the one-way chains may be efficiently computed in a time-memory trade. The complete description of the DeMA protocol in the case of the discrete squaring function is given and also some experimental results are presented which help on understanding the computational performance of the protocol. By using this implementation of the DeMA protocol message authentication can be assured at the cost of almost one modular multiplication for each exchanged message