On the effectiveness of blockchain against cryptocurrency attacks

Cryptocurrencies are being widely adopted to perform various online-based transactions; therefore, they are required to maintain a consensus to ensure a secured transaction. Blockchain comprises a distributed ledger, which holds digital records of individual crypto-transactions. Besides recording a particular activity, blockchain also ensures that the contents of the ledger are decided based on agreements of distinct participants. Various consensus mechanisms are followed by blockchain to ensure blocks are being summed up representing legitimate data on the network. However, the major consensus protocols comprise various limitations; and these are prone to different types of cyber attacks, such as Distributed denial-of-service, 51% attack, Double-spending, Long-range attack. In this paper, we analyze several attack vectors that can cause serious security threats due to the loopholes in the consensus mechanism. Our study involves examining 3 significant consensus mechanisms, which are followed by major cryptocurrencies. We also discuss the limitations of individual consensus mechanisms and demonstrate their robustness towards various attack vectors. We conclude that, although blockchain comprises proper consensus mechanisms to enhance secured crypto-transaction, unfortunately, it is not strong enough to defend against some cryptocurrency attacks which could discourage some users to adopt this technology.