Preventing Sybil Attack in Blockchain using Distributed Behavior Monitoring of Miners

Blockchain technology is useful with the record keeping of digital transactions, IoT, supply chain management etc. However, we have observed that the traditional attacks are possible on blockchain due to lack of robust identity management. We found that Sybil attack can cause severe impact in public/permissionless blockchain, in which an attacker can subvert the blockchain by creating a large number of pseudonymous identities (i.e. Fake user accounts) and push legitimate entities in the minority. Such virtual nodes can act like genuine nodes to create disproportionately large influence on the network. This may lead to several other attacks like DoS, DDoS etc. In this paper, a Sybil attack is demonstrated on a blockchain test bed with its impact on the throughput of the system. We propose a solution directive, in which each node monitors the behavior of other nodes and checks for the nodes which are forwarding the blocks of only particular user. Such nodes are quickly identified, blacklisted and notified to other nodes, and thus the Sybil attack can be restricted. We analyze experimental results of the proposed solution.