Titans Journal Day 35: The Immutability Debate

Immutability is one of the key characteristics of the blockchain. Once written on the blockchain, data cannot be altered, in theory. Smart contracts are deployed to the blockchain, hence they cannot be altered once deployed. Cryptocurrency transactions happen on the blockchain, too, and the transactions, once successful, cannot be reverted. That is by design.

On June 17, 2016, US$3.6 million worth of Ether (the cryptocurrency for the Ethereum blockchain) was siphoned out from the DAO through an exploit to the vulnerability of the open-source smart contract code. That is about one-third of the total money raised for the DAO (Decentralized Autonomous Organization).

A team of seven core Ethereum developers led by the creator of the Ethereum, Vitalik Buterin, decided to hack the hacker; and they were successful. They moved the stolen Ether to another smart contract. But the concern remains as the vulnerability inside the DAO smart contract is still there and that may allow further exploitation.

A heated debate ensued after the incident between the "Code is King" camp where they believe immutability is the key for trust in blockchain (and smart contracts) and bad code, though unfortunate, should suffer the consequences. The other camp led by Vitalik wants to revert the hack by performing a "hard fork"--essentially turning back the clock to the day before the hack and continue from there.

If you want to read the whole story, here's a good article for you. Long story short, Ethereum has since forked into two branches: Ethereum Classic (ETC), the blockchain has the history of the hack recorded on-chain, and the Ethereum (ETH), the hard forked blockchain reverted the DAO attack.

As of today, May 9, 2020, the ETC market cap is around $831 million vs the market cap of Ethereum is at around $23 billion. And Ethereum continues to evolve.

Which camp would you have voted for?

There is also another way to change the "history" of a blockchain. Do you know what is it called? Feel free to leave your answers in the comment.