Constructions Based on General Assumptions

Our objective in this chapter is to present a construction of a digital signature scheme based on the minimal assumption (cf. Theorem 2.1) that one-way functions exist. Along the way we will see a relatively simple construction, due to Lamport, of a one-time signature scheme based on the same assumption. We warn the reader at the outset that efficiency will not be a consideration here; we aim instead for generality (first) and simplicity of exposition (second). Interestingly, although several improved constructions of one-time signatures from one-way functions or permutations are known, the construction of a CMA-secure signature described in this chapter is essentially the best known (from any of the general assumptions discussed in the previous chapter); improving the efficiency of this generic construction remains an interesting and important open question.