A sufficient condition for optimal domain extension of UOWHFs

Abstract

In this paper we will provide a non-trivial sufficient condition for UOWHF-preserving (or valid) domain extension which can be very easy to verify. Using this result we will prove very that all known domain extension algorithms are valid. This would be a nice technique to prove and to construct a valid domain extension. We also propose an optimal (with respect to both time complexity and key size) domain extension algorithm based on an incomplete binary tree. © Springer-Verlag 2005.