Paper 2019/1348

Consensus on Clock in Universally Composable Timing Model

Handan Kılınç Alper

Abstract

In blockchain space, there are elaborate proof-of-stake based protocols with some assumptions related to clock synchronization, i.e.~that all of them know the current time of the protocol. However, this assumption is satisfied by relying on the security of centralized systems such as Network Time Protocol (NTP) or Global Positioning System (GPS). Clearly, any attack on these systems (which happened in the past) can cause corruption of blockchains that rely on the clock that they provide. To solve this problem in the nature of the decentralized network, we first define a general universally composable (GUC) model that captures the notion of consensus on a clock. Simply, a consensus clock is a clock that is agreed upon by honest parties by considering the clocks of all parties. In the end, we give a simple but useful protocol relying on a blockchain network. Our protocol is secure according to our new model. It can be used by full nodes of a blockchain who need to have a common time notion to preserve the correctness and the security of the blockchain protocol. One advantage of our protocol is that it does not cause any extra communication overhead on the underlying blockchain protocol.