Proposal and Evaluation of the Digital Certificate System with Sumi-coating Module for Privacy Protection

PKI (Public Key Infrastructure) is a system to secure procedures on the Internet with a digital signature using the public key cryptosystem. In this system, a trusted certification authority enables the authentication of communicators and/or signers using digital certificate published from the certificate authority. The digital certificate contains information such as names or addresses, etc., which can be used to identify the individual, although a common opinion is it is a privacy problem to disclose such information. In this paper, therefore, we propose a digital certificate system using the revised sumi-coated signature to solve the privacy as well as the security problems. We also report the evaluated results on the function and the performance using a partially implemented system.