Cryptology ePrint Archive: Report 2009/434

Tight Bounds for Protocols with Hybrid Security

Matthias Fitzi and Dominik Raub

Abstract: We consider broadcast and multi-party computation (MPC) in the setting where a digital signature scheme and a respective public-key infrastructure (PKI) are given among the players. However, neither the signature scheme nor the PKI are fully trusted. The goal is to achieve unconditional (PKI- and signature-independent) security up to a certain threshold, and security beyond this threshold under stronger assumptions, namely, that the forgery of signatures is impossible and/or that the given PKI is not under adversarial control. We give protocols for broadcast and MPC that achieve an optimal trade-off between these different levels of security.

Category / Keywords: cryptographic protocols / multi-party computation, broadcast, hybrid security

Date: received 4 Sep 2009, last revised 15 Sep 2010

Contact author: raub at cs au dk

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Version: 20100915:122724 (All versions of this report)

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