ABSTRACT
It was the 2008 Whitepaper penned by Satoshi Nakamoto and subsequently the January 3, 2009, that the world was introduced to the concept of decentralized cryptocurrencies through the Bitcoin’s system. This cryptocurrency quickly gained a huge amount of popularity. As a result, many other cryptocurrencies were born following its success. The years that followed the rise of Bitcoin saw a huge involvement of research communities spanning individuals, academia as well as industry, experimenting and formulating sound theoretical foundations behind the concept. Later, Ethereum (Buterin, 2014) was introduced to the world in the year 2015. Ethereum went on to become the second most popular blockchain-based system because it practically exemplified that blockchain as a concept can be decoupled from the notion of cryptocurrencies through its capability of processing smart contracts.
After Bitcoin’s birth, it didn’t take long for the research community to recognize that cryptocurrency, even though it sounds very attractive, is not the main aspect of this system. The main aspect of this system was the Blockchain—a decentralized, distributed ledger that is maintained among a peer-to-peer network of computers through consensus. Research in the field of blockchain is sprawled out over a variety of subdomains-consensus, cryptography, proof-of-work, privacy, network—to name a few. In this chapter, the primary aim is to aggregate the existing attacks on blockchain-based systems. Consensus mechanism forms the spinal cord of any successful blockchain-based system. All other aspects of these systems 202have their roots somewhere in the consensus mechanism followed in that system. In earlier sections, this provides an intuitive foundation on the most pervasive consensus mechanism currently employed by the leading distributed-ledger-technologies in this world—the proof of work. In the later sections of the chapter, a historical account of the variety of attacks that have been performed against blockchain-based systems is covered. In the last section, the chapter highlights some of the proposed models of attacks that have not been demonstrated at large yet but, are in currently seen as a possibility and therefore, are under research.
This chapter will be aimed at affording the reader with an exposition catalog of the existing attacks on the blockchain-based systems, from a perspective of awareness.
