Hardware Architecture and Cost/time/data Trade-off for Generic Inversion of One-Way Function Arquitectura en Hardware y Compromiso de Costo, Tiempo y Datos para Inversiones Genéricas de Funciones Unidireccionales

Abstract In many cases, a cryptographic algorithm can be viewed as a one-way function, which is easy to compute in forward direction but hard to invert. Inverting such one-way function amounts to breaking the algorithm. Time-Memory Trade-Off (TMTO) is a twenty five years old generic technique for inverting one-way functions. The most feasible implementation of TMTO is in special purpose hardware. In this paper, we describe a systematic architecture for implementing TMTO. We break down the offline and online phases into simpler tasks and identify opportunities for pipelining and parallelism. This results in a detailed top-level architecture. Many of our design choices are based on intuition. We develop a cost model for our architecture. Analysis of the cost model shows that 128-bit keys seem safe for the present. However, key sizes less than 96 bits do not provide comfortable security assurances.