A public blockchain is a permissionless, non-restrictive distributed ledger system. Anyone with internet access can sign up for a blockchain platform to become an authorized node and join the blockchain network. A node or user which is a part of the public blockchain is authorized to access current and past records, verify transactions or do proof-of-work for an incoming block, and do mining. The most basic application of public blockchains is for cryptocurrency mining and exchange. As a result, Bitcoin and Litecoin blockchains are the most commonly used public blockchains. If users strictly adhere to security rules and methods, public blockchains are mostly secure. However, it is only dangerous when participants do not strictly adhere to the security protocols.