By design, blockchains are inherently resistant to modification of blockchain distributed ledger data. Once recorded, the data in any given block cannot be altered retroactively without the alteration of all subsequent blocks, which requires collusion of the network majority.
The bitcoin design has been the inspiration for other applications. The first work on a cryptographically secured chain of blocks was described in 1991 by Stuart Haber and W. The first blockchain was conceptualised by an anonymous person or group known as Satoshi Nakamoto in 2008. In January 2015, the size had grown to almost 30GB, and from January 2016 to January 2017, the bitcoin blockchain grew from 50GB to 100GB in size. 0 technologies go beyond transactions and enable “exchange of value without powerful intermediaries acting as arbiters of money and information”. 0 platform, that would explore the use of blockchain-based automated voting systems.
IBM opened a blockchain innovation research center in Singapore in July 2016. They further predicted that, while foundational innovations can have enormous impact, “It will take decades for blockchain to seep into our economic and social infrastructure. A blockchain facilitates secure online transactions. A blockchain is a decentralized and distributed digital ledger that is used to record transactions across many computers so that the record cannot be altered retroactively without the alteration of all subsequent blocks and the collusion of the network. This allows the participants to verify and audit transactions inexpensively. This blockchain-based exchange of value can be completed more quickly, more safely and more cheaply than with traditional systems.
A blockchain database consists of two kinds of records: transactions and blocks. The linked blocks form a chain. Some blockchains create a new block as frequently as every five seconds. Sometimes separate blocks can be produced concurrently, creating a temporary fork.
In addition to a secure hash based history, any blockchain has a specified algorithm for scoring different versions of the history so that one with a higher value can be selected over others. Blocks not selected for inclusion in the chain are called orphan blocks. Peers supporting the database have different versions of the history from time to time. They only keep the highest scoring version of the database known to them. There is never an absolute guarantee that any particular entry will remain in the best version of the history forever. By storing data across its network, the blockchain eliminates the risks that come with data being held centrally.