Maintaining authenticated communication in the presence of break-ins
Ran Canetti, Shai Halevi, Amir Herzberg · 1997
We study the problem of maintaining authenticated communication over untrusted communication channels, in a scenario where the communicating parties may be occasionally and repeatedly broken into for limited periods of time.Once a party is broken into, its cryptographic keys are exposed and perhaps modified.We describe a mechanism that allows a party whose security has keen compromised to regain its ability to communicate in an authenticated way.The contribution of this paper is twofold.First we present a mathematical model for analyzing this scenario, and exhibit various properties and parameters of this model.Next we describe a practically-appealing protocol which enables parties to maintain authenticated communication in the presence of such a powerful adversary.For this protocol we use a variation of the proactive distributed signature schemes which were recently described by Herzberg et al.Although these schemes are designed for a model where authenticated communication and broadcast primitives are available, we show how they can be modified to work in our model, where no such primitives are available a-priori.We also present a new proactive distributed signature scheme with improved round and communication complexities.