Paper 2003/047

A Construction of 100 bit Public-Key Cryptosystem and Digital Signature Scheme

Masao KASAHARA and Ryuichi SAKAI

Abstract

Extensive studies have been made of the public-key cryptosystems based on multivariate polynomials . However most of the proposed public-key cryptosystems of rate 1.0 based on multivariate polynomials, are proved not secure. In this paper, we propose several types of new constructions of public-key cryptosystems based on two classes of randomly generated simultaneous equations, namely, a class based on bijective transformation and another class based on random transformation. One of the features of the proposed cryptosystems is that the sets of random simultaneous equations significantly improve the utilization factor of the public-key space. We show an example of the proposed cryptosystem whose size is only 100 bits that seems to be apparently secure in a sense that the utilization factor is significantly large compared with the conventional public-key cryptosystems.