What is a blockchain?
We can say that a blockchain is a continuously growing list of digital records, called blocks that are linked and secured using cryptography. Each block contains: data, previous hash (except for the Genesis block), and it’s own hash
The concept of Blockchain came from Stuart Haber and W. Scott Stornetta. In 1991 they published a paper named How to Time-Stamp a Digital Document. In this document they propose a solution using cryptography to certify the authenticity of documents stored in a “digital safety-deposit box”. The Abstract found in the first paragraph of How to Time-Stamp a Digital Document states the following: “The prospect of a world in which all text, audio, picture, and video documents are in digital form on easily modifiable media raises the issue of how to certify when a document was created or last changed. The problem is to time-stamp the data, not the medium. We propose computationally practical procedures for digital time-stamping of such documents so that it is infeasible for a user either to back-date or to forward-date his document, even with the collusion of a time-stamping service. Our procedures maintain complete privacy of the documents themselves and require no record-keeping by the time-stamping service”.
Blockchain is a ledger on a distributed peer to peer network which makes it immutable. This means that since it’s not controlled by a central entity, no changes can be made to the data once it is registered in the blockchain. A great benefit that blockchain provides is that all peers connected to the network hold a copy of the complete ledger and this allows full transparency and authenticity of all transactions.
Bitcoin is a good example of how cryptocurrencies and blockchain work together. When computers (also known as miners) connected to the network are able to validate transactions, they get rewarded with Bitcoin.
We are now starting to see companies and organizations using this technology of blockchain since it solves authenticity of their transactions and it offers protection and transparency.
*References: “How to Time-Stamp a Digital Document” by Stuart Haber and W. Scott Stornetta