Protocol Initialization for the Framework of Universal Composability.
Boaz Barak, Yehuda Lindell, Tal Rabin · 2004
Universally composable protocols (Canetti, FOCS 2000) are cryptographic protocols that remain secure even when run concurrently with arbitrary other protocols. Thus, universally composable protocols can be run in modern networks, like the Internet, and their security is guaranteed. However, the de nition of universal composition actually assumes that each execution of the protocol is assigned a unique session identi er, and furthermore, that this identi er is known to all the participating parties. In addition, all universally composable protocols assume that the set of participating parties and the speci cation of the protocol to be run are a-priori agreed upon and known to all parties. In a decentralized network like the Internet, this setup information must be securely generated by the parties themselves. In this note we formalize the setup problem and show how to securely realize it with a simple and highly ecient protocol.