Brief Announcement: ZeroBlock: Timestamp-Free Prevention of Block-Withholding Attack in Bitcoin

Abstract

Bitcoin was recently introduced as a peer-to-peer electronic currency in order to facilitate transactions outside the traditional financial system. The core of Bitcoin, the Blockchain, is the history of all transactions committed by the system. This distributed ledger is similar to a distributed shared register where miners write and read blocks. New blocks in the Blockchain contain the last transactions in the system and are added by miners after a block mining process that consists in solving a difficult cryptographic puzzle. Although, the reward is the main motivation for the mining process in Bitcoin, it also may be an incentive for attacks such as selfish mining. In this paper we propose and theoretically analyze a solution for one of the major problems in Bitcoin: selfish mining or block-withholding attack. This attack is conducted by adversarial miners in order to either earn undue rewards or waste the computational power of honest miners. Contrary to the best to date solution for preventing block-withholding [6], our solution, ZeroBlock, prevents this attack by using a novel timestamp-free technique that exploits the Poisson nature of the proof-of-work and the current knowledge on the propagation of information in Bitcoin [2]. Note that previous solutions are vulnerable to forgeable timestamps. Additionally, our solution is compliant with miners churn.