The Hierarchy of Key Evolving Signatures and a Characterization of Proxy Signatures

For the last two decades the notion and implementations of proxy signatures have been used to allow transfer of digital signing power within some context (in order to enable flexibility of signers within organizations and among entities). On the other hand, various notions of the key-evolving signature paradigms (forward-secure, key-insulated, and intrusion-resilient signatures) have been suggested in the last few years for protecting the security of signature schemes, localizing the damage of secret key exposure. In this work we relate the various notions via direct and concrete security reductions that are tight. We start by developing the first formal model for fully hierarchical proxy signatures, which, as we point out, also addresses vulnerabilities of previous schemes when self-delegation is used. Next, we prove that proxy signatures are, in fact, equivalent to key-insulated signatures. We then use this fact and other results to establish a tight hierarchy among the key-evolvin...

• Type: Conference
• Year: 2004
• Where: EUROCRYPT
• Authors: Tal Malkin, Satoshi Obana, Moti Yung
• Keywords: Cryptography, EUROCRYPT 2004, Intrusion-resilient Signatures, Proxy Signatures, Various Notions