Trading Static for Adaptive Security in Universally Composable Zero-Knowledge

Adaptive security, while more realistic as an adversarial model, is typically much harder to achieve compared to static security in cryptographic protocol design. Universal composition (UC) provides a very attractive framework for the modular design of cryptographic protocols that captures both static and adaptive security formulations. In the UC framework, one can design protocols in hybrid worlds that allow access to idealized functionalities and then apply the universal composition theorem to obtain more concrete protocol instances. The zero-knowledge (ZK) ideal functionality is one of the most useful sub-protocols in modular cryptographic design. Given an adaptively secure protocol in the ideal ZK-hybrid-world do we always need an adaptively secure realization of the ZK functionality in order to preserve adaptive security under composition? In this work, perhaps surprisingly, we find that this is not so and in fact there are useful protocol instances that we can “trade static se...

• Type: Conference
• Year: 2007
• Where: ICALP
• Authors: Aggelos Kiayias, Hong-Sheng Zhou
• Keywords: Adaptive Security, Cryptographic Protocols, ICALP 2007, Programming Languages, Static Security