Network Time with a Consensus on Clock

Decentralized protocols which require synchronous communication usually achieve it with the help of the time that computer clocks show. These clocks are mostly adjusted by centralized systems such as Network Time Protocol (NTP) because these adjustments are indispensable to reduce the effects of random drifts on clocks. On the other hand, an attack on these systems (which has happened in the past) can cause corruption of the protocols which rely on the time data that they provide to preserve synchronicity. So, we are facing the dilemma of relying on a centralized solution to adjust our timers or risking the security of our decentralized protocols. In this paper, we propose a Global Universal Composable (GUC) model for the physical clock synchronization problem in the decentralized systems by modeling the notion of consensus on clocks. Consensus on clocks is agreed upon considering the local clocks of all parties in a protocol which are possibly drifted. In this way, we model the functionality that e.g. NTP provides in a decentralized manner. In the end, we give a simple but useful protocol relying on a blockchain network that realizes our model. Our protocol can be used by the full nodes of a blockchain that need synchronous clocks in the real world 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

Overview of Polkadot and its Design Considerations

In this paper we describe the design components of the heterogenous multi-chain protocol Polkadot and explain how these components help Polkadot address some of the existing shortcomings of blockchain technologies. At present, a vast number of blockchain projects have been introduced and employed with various features that are not necessarily designed to work with each other. This makes it difficult for users to utilise a large number of applications on different blockchain projects. Moreover, with the increase in number of projects the security that each one is providing individually becomes weaker. Polkadot aims to provide a scalable and interoperable framework for multiple chains with pooled security that is achieved by the collection of components described in this paper