Comment on an Improved Signature without Using One-Way Hash Functions

Abstract

In 2005, Zhang and Wang proposed an improved signature scheme without using one-way hash functions. Even they used bit wise exclusive-or to against multiplicative attack, and the exclusive-or is easy to implement, and more fast. But they may have misused order of operation in mathematical precedence. In this comment, we would like to point out an error in the related work and scheme as follows.