Review of Security Aspects of 51 Percent Attack on Blockchain

Blockchain technology has emerged as a secure technology for performing financial transactions. It is a database which stores all the transactions into blocks. It has made the digital data decentralized and thus does not have the problem of single point failure. The newly created transaction is broadcasted to all other nodes in the network. Although blockchain has the property of immutability but it is always prone to the cyber attacks. The 51 percent is the predominant attack encountered over blockchain which is executed forming large mining pools. This is the attack over block addition processwhere maliciously mined blocks get added to blockchain. This paper encapsulates the critical review of existing solutions in the context of 51 percent attack so as to get the analysis of level of protection and the challenges in the existing methods.