A block-chain is continuosly pileing up record of transactions. High integrity being one of the major advantages of block-chain , it uses digital signatures which will ensure that the transactions authenticity is intact and that no one can ever tamper with it. Block-chain therefore, uses the security and openess traits of cryptography and internet respectively to give everyone a safer and faster way to transact.How Block-chain functions?Block-chain is a decentralised technology, that is, backed by many and controlled by none. So , this block of data are deployed among multiple infrastructure. These multiple layers in the infrastructure help in providing consensus about the transaction’s state at any given point of time; they all have duplicate copies of the existing authenticated block distributed amongst them. These multiple deployment infrastructure are commonly known as nodes/ledgers.Since the consensus are distributed it allows blockchain to run in a distributed environment without the requirement for any central authority to verify the transactions. Therefore, Block-chain applications could easily give decentralized systems an edge over centralized systems where validations comes from the consensus which is derived from multiple nodes/ledgers.When a new transaction or any updates to an existing transaction takes place, some algorithms implemention in the nodes within a blockchain are executed and eventually validate and verify the history of the individual block in the block-chain, and come to a consensus that the signature and history is correct, then the new transaction is added and a new block is inserted to the chain of transactions. If majority of nodes do not agree with the modification of the entry, then it will be denied and not inserted to the chain. Block-chain can be configured in such a way that the to achieve consensus on transactions you could use different rules. For example, you can set nodes to known participants in the chain and exclude every other node. So, you can configure a private ledger as mentioned above or a public ledger in which anyone can participate. So basically, a blockchain needs to do two things:-1. Gather and order data into blocks2. Chain these blocks together securely using cryptography.