Efficient commitment schemes with bounded sender and unbounded receiver

Abstract

In this paper we address the problem of commitment schemes where the sender is bounded to polynomial time and the receiver may be all powerful. We present a scheme for committing to a (possibly long) string. Our scheme is efficient in the following three ways: Round Efficiency: Each part of the scheme consists of a single round. Low Communication: The number of bits required for the commitment equals the security parameter of the system, regardless of the length of the string which is being committed to. Fast Implementation: The time taken to commit to a string is linear in the length of the string and almost linear in the security parameter of the system.