A Certificateless Ordered Sequential Aggregate Signature Scheme Secure

against Super Adversaries

Naoto Yanai⁺¹, Raylin Tso², Masahiro Mambo³, and Eiji Okamoto⁴

^1,4Graduate School of Systems and Information Engineering

University of Tsukuba

Tsukuba, Japan

²Department of Computer Science

National Chengchi University

Taipei, Taiwan

³Institute of Science and Engineering

Kanazawa University

Kanazawa, Japan

Abstract

Certificateless cryptosystem is a hybrid scheme of traditional PKI and ID-based scheme

and has positive aspects of both of PKI and ID-based cryptosystem,

i.e. solving key escrow problem and certificate management problem simultaneously.

Cryptographic schemes constructed in such a hybrid setting, generally called certificateless setting,

retain these positive aspects and have been extensively studied recently.

To the best of our knowledge, an ordered sequential aggregate signature (OSAS) scheme,

which is a signature scheme verifying both the validity of a document and a signing order of a group of signers,

has never been proposed in the certificateless setting. Therefore we propose an OSAS scheme in a certificateless setting

called certificateless ordered sequential aggregate signature (CLOSAS) scheme.

Our proposed scheme has advantages in its communication cost and the security proof.

In particular, its signature size is fixed with respect to the number of signers, and the security

is proven in the random oracle model against super adversaries that are the strongest adversary

in certificateless signature scheme. Our scheme resists KGC’s malicious activities associated with key escrow

and forgery of signatures as long as both of each user and KGC involve directly in a key generation.

Keywords: Key escrow problem, certificateless setting, ordered sequential aggregate signature scheme,

super adversary, random oracle model, full aggregation

+: Corresponding author: Naoto Yanai

SB822, Third Area, University of Tsukuba, Tennoudai 1-1-1, Tsukuba-city, Ibaraki, Japan,

Phone: +81-029-853-5600 (ext: 8208)

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

Vol. 3, No. 1/2, pp. 30-54, March 2012 [pdf]