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Author Topic: Importance of Speed  (Read 1089 times)
kevorsen (OP)
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February 24, 2014, 12:32:19 PM
 #21

Higher block speed also puts you at unique security disadvantages, as propagation time amongst all nodes becomes an issue.  The larger the network and blocksize, the greater this becomes an issue.

Basically, the tradeoff is like this: In PoW, blocks contain many tx.  To effectively be a solution for the Two General's Problem, each node relaying a new block must download and verify its contents completely before doing so.  However, a malicious attacker instead begins generating a bunch of his own blocks that are not revealed to the network.  Because the miner does not have to rely on his blocks being relayed throughout the network, he is given an advantage in terms of being able to perform a 51% attack and can now do so with less than 51%; in the case of very fast blocks with large block sizes, this is probably way less than 51%.

People will likely find this out as soon as an exchange loses a lot of money on a double spend; then you need to crank the block size down, and end up overall with not much of an advantage compared to Bitcoin when you're considered tx/sec, and you'll likely have to spend more in fees just to get your tx confirmed quickly because the supply of tx in a block is greatly diminished while demand runs the same.

Anyway, don't say I didn't warn you...

I did a fair bit of research, and spoke to some creator of coins.
and I want to counter argue that the above scenario is extremely unlikely/impossible, and the only way to do it, is to have a 51% attack.

Also point being, if it is possible, it would have already happened, given the huge volume daily and profit bounty.

I would like to ask Tachotime, why do you even think it is possible? I want to learn what you see.
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February 24, 2014, 08:33:52 PM
 #22

^^ there is a mathematical explanation in the GHOST paper. See figure 1 for actual data on block propagation times with varying block sizes.

If anyone is insisting you need >50% of the network hash rate to double spend, they're incorrect. That's simply the quantity of hash rate required so that on average you are able to double spend 100% of the time. You can do it with a lesser hash rate, with lower probability.

Because it's possible doesn't mean it'll happen -- deepbit and litecoinpool were often > 51% and attacks never occurred. But when you have a poorly secured new coin...

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