Quote from: amincd on June 07, 2011, 04:25:46 AM

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1. as has been pointed out many times, the attack is not expensive,

Tens of millions of dollars for hardware, and millions more for manpower is expensive for most groups in the world.

by all the calculations given in other discussions, it's not nearly that expensive. i'm pretty sure i have the resources to do it myself, if i were of such a mind. many small corporations could easily do it.

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the oft-repeated statistic about bitcoin being the largest supercomputer or exceeding 500 others is silly and almost intentionally misleading. many 3d-intensive games are much larger 'supercomputers' on the same metric, as probably is the global dns system or smtp.

What do you mean many 3d-games have more hashing power than the top 500 supercomputers? You mean 3d MMOG server farms? Do you have any statistics on this? I'd like to learn more.

than bitcoin. many games are likely running the equivalent of more than a few thousand gpus at any given moment.

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A strategic attack would not be profitable because it would benefit not only the attacker, but the attacker and all competing currencies. If an attack is done by someone with a stake in a bitcoin variant, it would undermine the very concept and be unprofitable.

this is too glib an objection. what if the variant is not subject to that particular attack vector?

you seem to want a 'magic bullet' response to all my points, but there isn't one, and the search is in vain. instead, what matters are overall likelihoods. you can respond with a better theoretical threat assessment, but mere dismissal of attacks by this community is not going to serve the technology well.

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this neglect of the strategic value of an attack is the only well-known significant mistake in satoshi's
original paper, one that the analyst going by the name 'computerscientist' in various online forums has pointed out in detail.

A strategic attack could certainly be valuable to someone for ideological/non-monetary reasons, I just don't see any reason to think it could be profitable.

pump-and-dump spam for a penny stock may cost a lot, but it can have significant gains from market manipulation if it escapes regulation. the same is true of many attacks on bitcoin.

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2. the attack is not easy to detect. please outline a mechanism for detection in the general case if you think you have one. the general problem is that the only response to a proof-of-work attack is greater work; it's very difficult in practice to distinguish 'good' work from 'bad' work.

People start complaining about bitcoins they received suddenly being unconfirmed.

and among the several possibilities, which of the complainers are 'honest' and which are part of the attack? by what (non-bitcoin, non-proof-of-work) procedure is meta-consensus reached? do we go by reputation in the forum? (if so, is that for sale, and at what price?) an attack like the overflow bug in october(?) would, if it happened today, practically be irreversible unless we want to give up a significant part of bitcoin's decentralisation. and a bug like that, if timed strategically by an intelligent market manipulator, could divest the currently prominent block chain of almost all its value.