STOC '87 Proceedings of the nineteenth annual ACM symposium on Theory of computing
Universally composable two-party and multi-party secure computation
STOC '02 Proceedings of the thiry-fourth annual ACM symposium on Theory of computing
Foundations of Cryptography: Basic Tools
Foundations of Cryptography: Basic Tools
Universally Composable Commitments
CRYPTO '01 Proceedings of the 21st Annual International Cryptology Conference on Advances in Cryptology
On Adaptive vs. Non-adaptive Security of Multiparty Protocols
EUROCRYPT '01 Proceedings of the International Conference on the Theory and Application of Cryptographic Techniques: Advances in Cryptology
Universally Composable Notions of Key Exchange and Secure Channels
EUROCRYPT '02 Proceedings of the International Conference on the Theory and Applications of Cryptographic Techniques: Advances in Cryptology
CRYPTO '02 Proceedings of the 22nd Annual International Cryptology Conference on Advances in Cryptology
Universally Composable Security: A New Paradigm for Cryptographic Protocols
FOCS '01 Proceedings of the 42nd IEEE symposium on Foundations of Computer Science
Universally Composable Signature, Certification, and Authentication
CSFW '04 Proceedings of the 17th IEEE workshop on Computer Security Foundations
Universally Composable Protocols with Relaxed Set-Up Assumptions
FOCS '04 Proceedings of the 45th Annual IEEE Symposium on Foundations of Computer Science
Cryptographic protocols provably secure against dynamic adversaries
EUROCRYPT'92 Proceedings of the 11th annual international conference on Theory and application of cryptographic techniques
Relaxing environmental security: monitored functionalities and client-server computation
TCC'05 Proceedings of the Second international conference on Theory of Cryptography
Equivocal blind signatures and adaptive UC-security
TCC'08 Proceedings of the 5th conference on Theory of cryptography
| Hi-index | 0.00 |
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 security for adaptive security." We investigate the above setting, by introducing a weakened ZK ideal functionality, called the ideal leaking-zero-knowledge functionality (LZK) that leaks some information about the witness to the adversary in a certain prescribed way. We show that while LZK is interchangeable to ZK against static adversaries, ZK is more stringent when adaptive adversaries are considered. We then proceed to characterize a class of protocols in the hybrid-ZK-world that can be "transported" to the LZK-hybridworld without forfeiting their security against adaptive adversaries. Our results demonstrate that in such settings a static protocol realization of ZK is sufficient for ensuring adaptive security for the parent hybrid protocol something that enables simplified and substantially more efficient UC realizations of such protocols.