Blockchain Immutability: A myth or reality?

[Abiky]

Back in 2016, the Ethereum blockchain suffered a DAO hack which caused millions of dollars in ETH to become siphoned by the hacker. Due to the losses this has caused to investors of The DAO, the Ethereum foundation agreed to roll back the Ethereum blockchain. Prior to such events, the Ethereum blockchain was immutable. However, after transactions were rolled back, it was shown that immutability could be violated in the event there's a compromise on the network.

As such, I'm beginning to wonder if blockchain immutability is a myth or a reality? After all, in PoW blockchains, if there's a 51% attack, the hacker could easily revert transactions at will, compromising the immutability of a specific cryptocurrency. So far, Bitcoin has been immutable in every way. However, that could easily be broken with a double-spending attack within the future.

What are your thoughts?

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[tuthienloc92bk]

After all, in PoW blockchains, if there's a 51% attack, the hacker could easily revert transactions at will, compromising the immutability of a specific cryptocurrency.

I agree with you. But, to perform a 51% attack is easy? That is a key point. With the aid of PoW network, blockchain is really immutability unless this network is too weak. So, I think immutability is reality.

[Abiky]

I agree with you. But, to perform a 51% attack is easy? That is a key point. With the aid of PoW network, blockchain is really immutability unless this network is too weak. So, I think immutability is reality.

You do have a point there, mate. The bigger a PoW blockchain is, the harder it will be for the attacker to successfully perform a 51% attack and alter transaction history. Considering how Bitcoin is the world's largest cryptocurrency in hashrate, it's extremely expensive to achieve such an attack. However, the real problem lies when a PoW cryptocurrency becomes smaller in hashrate. If at any point in time, Bitcoin becomes smaller in hashrate, then a 51% attack would become cheaper to perform, violating the principles of immutability.

As such, a cryptocurrency or blockchain is immutable if there's proper hashrate distribution among miners. Considering that it’s possible to revert transactions and perform double-spending attacks, immutability within Bitcoin or any other cryptocurrency is not guaranteed. Which is why, I believe that immutability is a myth as transactions can be easily reverted (like ETH's DAO hack) when there's a high concentration of hashrate within a single entity.

Nonetheless, I hope that Bitcoin remains immutable forever. Otherwise, people would lose trust in it as a decentralized cryptocurrency for daily payments without middleman.