> "Is a decentralized database that stores a registry of assets and transactions across a peer-to-peer network. Is basically a public registry of who owns what and who transacts what. The transactions are secured by cryptography, and over time, that transaction history gets locked in blocks of data that are then cryptographically linked together and secured. This creates an immutable, unforgeable record of all the transactions across this network. This record is replicated on every computer that uses the network."
>
> --Bettina Warburg<sup>1</sup>
Blockchain is often associated with Bitcoin and other cryptocurrencies, but they are not the same thing. Bitcoin was the first to implement the concept of the Blockchain. The structure of a blockchain, a growing list of records, can be applied to many other fields such as digital identity, supply chain and even [democracy](https://www.democracy.earth/).
Even though blockchain can be applied to a big range of problems, it is not the solution to everything. This technology is usually used to solve problems where the parties don't trust each other.
A third party is usually needed to validate trust relationships. In the most common example, which is the banking system, a trusted authority is needed, such as a bank, to intermediate transactions, manage accounts, verify balances, and validate transfers. Blockchain then, comes in this case to replace the regulatory authority. In the case of cryptocurrencies, it replaces the figure of the bank, doing all the validations and guaranteeing the security and veracity in the transactions.
For this reason Blockchain is also known as **"The Trust Protocol"**.
### History
The first work on a cryptographically secured chain of blocks was described in 1991 by Stuart Haber and W. Scott Stornetta. They wanted to implement a system where documents' timestamps could not be tampered with or backdated. In 1992, Bayer, Haber and Stornetta incorporated Merkle trees to the design, which improved its efficiency by allowing several documents to be collected into one block.
The first blockchain was conceptualized by a person (or group of people) known as Satoshi Nakamoto in 2008. It was implemented the following year by Nakamoto as a core component of the cryptocurrency bitcoin, where it serves as the public ledger for all transactions on the network.
In August 2014, the bitcoin blockchain file size, containing records of all transactions that have occurred on the network, reached 20 GB (gigabytes). In January 2015, the size had grown to almost 30 GB, and from January 2016 to January 2017, the bitcoin blockchain grew from 50 GB to 100 GB in size. Furthermore, Nakamoto introduced the concept of proof of work to ensure a more decentralised trust in the records' security.
The words block and chain were used separately in Satoshi Nakamoto's original paper, but were eventually popularized as a single word, blockchain, by 2016. The term blockchain 2.0 refers to new applications of the distributed blockchain database, first emerging in 2014. The Economist described one implementation of this second-generation programmable blockchain as coming with "a programming language that allows users to write more sophisticated smart contracts, thus creating invoices that pay themselves when a shipment arrives or share certificates which automatically send their owners dividends if profits reach a certain level."
As of 2016, blockchain 2.0 implementations continue to require an off-chain oracle to access any "external data or events based on time or market conditions to interact with the blockchain."
#### Sources
1. [Bettina Warburg, "How the blockchain will radically transform the economy", *TED Talks*, December 8, 2016](https://youtu.be/RplnSVTzvnU?t=213)
##### More information
* [WTF is The Blockchain?](https://hackernoon.com/wtf-is-the-blockchain-1da89ba19348)
* [Blockchain: the revolution we’re not ready for](https://medium.freecodecamp.org/blockchain-is-our-first-22nd-century-technology-d4ad45fca2ce)
* [How the blockchain is changing money and business | Don Tapscott (YouTube video)](https://www.youtube.com/watch?v=Pl8OlkkwRpc)
* [Introduction to Bitcoin, Ethereum and Smart Contracts](https://github.com/WizardOfAus/WizardsEthereumWorkshop)
