Security Notions for Unconditionally Secure Signature Schemes

Abstract

This paper focuses on notions for the security of digital signature schemes whose resistance against forgery is not dependent on unproven computational assumptions. We establish successfully a sound and strong notion for such signature schemes. We arrive at the sound notion by examining carefully the more established security notions for digital signatures based on public-key cryptography, and taking into account desirable requirements of signature schemes in the unconditional security setting. We also reveal an interesting relation among relevant security notions which have appeared in the unconditionally setting, and significantly, prove that our new security notion is the strongest among all those for unconditionally secure authentication and signature schemes known to date. Furthermore, we show that our security notion encompasses that for public-key signature schemes, namely, existential unforgeability under adaptive chosen-message attack. Finally we propose a construction method for signature schemes that are provably secure in our strong security notion.