10/ Sure, you could put an arbitrary value on the penalty and claim that’s it’s a huge wall of defense, but because of the “weak subjectivity” vulnerability, there’s a small backdoor to the side of the castle, making the hugeness of the wall irrelevant.
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11/ I want to take the opportunity to put away the misguided idea of achieving better cost of attack/cost of defense ratio than 1:1.
@TuurDemeester also addressed this in his critique of PoShttps://medium.com/@tuurdemeester/critique-of-buterins-a-proof-of-stake-design-philosophy-49fc9ebb36c6 …1 reply 1 retweet 11 likesShow this thread -
12/ Take public-cryptography for example. One might cite it as an example of asymmetric attack/defense ratio.
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13/ However, it is only asymmetric from the point of view of the owner of the private key, and dependent on the fact that this key is forever kept secret. In other words, public-key cryptography security is *relative*.
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14/ You can defeat the asymmetry by somehow forcefully switching the roles: become the owner yourself.
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15/ The true cost analysis of attacking public-key cryptography must include social engineering attacks: kidnapping, extortion, torture. You can make attacking cost much lower than the cost of brute-forcing the key.
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16/ So anything that has asymmetric attack/defense ratio has to be relative. There’s always a way to go around the asymmetry.
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17/ PoW security, otoh, is *absolute*. It doesn't matter which frame of reference you come from, the cost of attack is the same. PoW ledger immutability is objective, it doesn’t care who you are.
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Replying to @hugohanoi
> It doesn't matter which frame of reference you come from, the cost of attack is the same. False. For example, if you have more than 23.21% hashpower, then selfish mining attacks are *profitable*. Successful 51% attacks are also *profitable*.
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Replying to @VitalikButerin
The fact that a miner can gain a compounding advantage is *orthogonal* to the issue of reverting the ledger. # of hash ops required to revert still must be equal to # of hash ops used to mine. THAT is absolute & an objective function that doesn’t change *regardless of PoV*.
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Hugo Nguyen Retweeted Hugo Nguyen
As for how to defeat centralization issue, that requires another source of energy. But again, the issues are orthogonal.https://twitter.com/hugohanoi/status/952418125508575233 …
Hugo Nguyen added,
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