ABSTRACT
Blockchain technology’s popularity is increasing in the industry day by day because of its excellent features, which provide transparency, scalability, and immutability. Blockchain technology provides security by a chain of blocks, which are connected through cryptography. This chain of blocks makes it immutable because an alteration to a single block means an alteration in all blocks after that block, and the same must be done to all the chains of all the participants in the network (at least 51%). This alteration is very difficult because of the requirement of massive computational power. But the security of a blockchain is very much dependent on the technology that is adopted by the blockchain. Mainly, blockchain is private or public, with two different features related to joining the chain, validating transactions or mining the transactions or consensus mechanism. These differences in the features can affect the security of the data moving in the network. Some new security measures must be defined to tackle such issues so that the security concerns become infrastructure-independent. This chapter focuses on a brief overview of blockchain technology with its functioning approach, security issues, and countermeasure approaches.
