Security Analysis of Offine E-cash Systems with Malicious Insider

Takashi Nishide⁺¹, Shingo Miyazaki², and Kouichi Sakurai³

^1,3Kyushu University

Fukuoka, Japan

¹nishide@inf.kyushu-u.ac.jp, ³sakurai@inf.kyushu-u.ac.jp

²Toshiba Solutions

Tokyo, Japan

Miyazaki.Shingo@toshiba-sol.co.jp

Abstract

When we build electronic cash systems, the main focus of the design is usually on preventing customers’

malicious actions. However, since authorities such as banks and certificate authorities may have

important secret data of customers, the insiders in the potentially untrusted authorities can become threats

to electronic cash systems. Miyazaki and Sakurai [2] first systematically analyzed security

of offline anonymous electronic cash systems by considering the insider threats from untrusted authorities.

They investigated the security of the existing electronic cash systems and categorized

the systems into four types. In this paper, we reconsider the security of offline anonymous electronic

cash systems including more recent systems based on the classification of Miyazaki and Sakurai and

investigate the possible effective countermeasures against malicious insiders.

Keywords: Chaum-Fiat-Naor paradigm, double spending, electronic cash system, framing attack by bank, insider threat

+: Corresponding author: Takashi Nishide

Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan, Tel: +81-92-802-3666,

Email: nishide@inf.kyushu-u.ac.jp, Web: http://itslab.inf.kyushu-u.ac.jp/~nishide/index.html

Journal of Wireless Mobile Networks, Ubiquitous Computing, and Dependable Applications (JoWUA),

Vol. 3, No. 1/2, pp. 55-71, March 2012 [pdf]