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Comment by rotten | Hacker News Reader

My understanding is that blockchain truth is determined via a majority vote. What I'm really not clear on is how someone with a botnet can't simply take over a blockchain. With such large sums of cash at stake, it seems like a serious hacker would be much more interested in controlling a blockchain than doing silly DDOS attacks on some corporate website that slighted them.

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Many of these systems are designed such that if you do have the computational power to attack the integrity of the chain, it is actually more profitable to put that power to use for legitimate mining.

Having 51% of the computational power does not let you just make up transactions on your own or transfer funds to your own wallet. What it does allow you to do is pay a counter-party, receive some product from them, and then go back and create a new chain where you paid yourself, instead of the counter-party.

The ethereum whitepaper has a nice explanation of this. https://github.com/ethereum/wiki/wiki/White-Paper

In normal PoW, if you own a botnet, unless your botnet has a significant % (something like 25-51% depend9ng on details) of global hash power you're economically incentiviced to work on the main chain rather than try to "take over" the network

PoW ?

“Prisoners of War”; in Aztec cryptocurrency mining, blocks are allocated based on captives taken in ritual combat, who are then sacrificed to prevent double counting.

Alternatively, “proof of work”, as used in Bitcoin.

For that you need to have more than half of the hash power of the blockchain, which means, for bitcoin at least, billions of hardware investment. A hacker can't have such power.

On the other hand someone with significant influence over a small group of Chinese people still can, and not every blockchain is going to be anywhere near as distributed as BTC

No, but a state actor might...

Many blockchain applications I've seen aren't distributed over millions of computer systems. Thousands, maybe. Hundreds for some.

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