Christian Badertscher, ETH Zurich
From 12.00 until 13.30
At CNB/F/110, ETH Zurich
Universitätstrasse 6, 8092 Zurich
Bitcoin is perhaps the most prominent example of a distributed cryptographic protocol that is extensively used in everyday life. In this talk, we present a universally composable treatment of the Bitcoin protocol. We specify the goal that Bitcoin aims to achieve as a ledger functionality in the universal composability (UC) model of Canetti. Unlike previous suggestions, which are arguably not implementable given the Bitcoin assumptions, our proposed ledger functionality is securely UC-realized by an appropriate abstraction of Bitcoin as a UC protocol, assuming that the majority of the mining power is honest.
We further motivate how this result lays the basis for future cryptographic analyses of Bitcoin that consider rational behavior. Such analyses would allow to identify what incentives make participants refraining from collaborative attacks against the Bitcoin network, even if building coalitions possessing more than 50% of the computing power was possible.