A company called Ethereum, founded by crypto-currency enthusiast and developer Vitalik Buterin, has built on the blockchain concept by making it programmable so that applications can be written to run on it.
This provides a basis for smart contracts, i.e. transactions programmed to run automatically when certain conditions are met. Ethereum also attempts to address some of the drawbacks of the bitcoin blockchain for everyday use, including speed of transaction and 'blockchain bloat' caused by having to store every transaction on the chain forever.
Ethereum has its own crypto-currency, the ether, and, despite being launched only in 2015, a number of projects based on Ethereum have already emerged, most notably the Decentralised Autonomous Organisation (DAO).
The DAO is a hub that acts as a funding source for third-party projects built on the Ethereum blockchain.
Unfortunately, the DAO's smart contract software had a flaw that allowed a hacker to syphon off about $50m in ether, a third of the total holdings, into a single wallet.
This led to a crash in the price of the ether, and a controversial hard-forking of Ethereum was pushed through to return it to the state before the hack. This means there are now two versions, Ethereum and Ethereum Classic.
The attack shows the inherent vulnerabilities in ground-breaking systems and may serve as a warning against going too fast too soon.
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