What is Blockchain
Blockchain is essentially a decentralized ,openly auditable, trustless ledger that can be shared and viewed by all users.Firstly it was used to enable bitcoin trading and serves as a secure accounting information system.The main feature of Blockchain is its capability to decentralize system management and authorization to a network of computers. All of these computers verify transaction which is based on specific rules which control all users’ actions. The verification process is controlled by all the computers for avoiding of failures.Blockchain is known by its 2 generations. The first generation was a public ledger that recorded information about trading the bitcoin in the form of a chain of interlocked blocks.In this generation any user can take a part in trading and contribute to the verification of the transaction. This verification is characterized by pre encoded rules such as the information about validated transactions are sended/posted on the Blockchain ledger. When transaction is already posted and confirmed, all related records will be sealed cryptographically and sheared between an entire chain. This process makes all falsifications and destroying records practically impossible. The main characteristic of blockchain of the first generation are decentralized , strongly authenticated and tamper resistant. Decentralization is characterized by the ability to access the entire list of transactions by everyone in the blockchain network. Furthermore the users can jointly operate and control the whole system. Strong authentication means that the identify of each participation ion blockchain transaction can be verified. And when a transaction is posted on the blockchain, it becomes unchangeable and irreversible what makes Blockchain tamper resistant. All these main Bockchain characteristics show that Blockchain serves as the foundation of a new accounting information system, that prevents all accounting records or related documents from being altered or deleted,or even shearing the information with other users. The second generation of Blockchain is famous by its new type of application called a “smart contract”. The smart contracts are “user-defined programs that specify rules-governing transactions” (Kevin Delmolino , Mitchell Arnett ,Ahmed Kosba ,Andrew Miller ,and Elaine Shi ,“Step by Step towards Creating a Safe Smart Contract,” Nov. 18, 2015). Smart contracts can securely operate on a blockchain; any party can perform verification of transactions in compliance with the embedded rules. More importantly ,blockchain users can create their own rules into a smart contract executing specific tasks.