Quote from: kalus on March 10, 2014, 10:28:21 PM

Quote from: rojuwah on March 10, 2014, 09:12:09 PM

Quote from: kalus on March 10, 2014, 04:58:24 AM

Quote from: Azeh on March 10, 2014, 03:50:36 AM

And how are you certain that they will not be able to protect the blockchain?

When figuring out what a currency is worth, the security of the blockchains should be considered. if the blockchain cannot be sufficiently distributed, the risk of transaction reversals or intentional forks should destroy any value in that coin. Because of this vulnerability most coins are overvalued.

nice point, but just a question about bitcoin: ok the total hash power is immense but a pool has >%40 hashpower alone and just two pools together suffice to exceed 50%, how about that?

the issue of the btc blockchain has been discussed exhaustively on btctalk, and there are many threads discussing your scenario. take a look also at the "weaknesses" section in bitcoin: https://en.bitcoin.it/wiki/Weaknesses

if two pools combine to exceed 50% of network hashrate this is problematic, but likely this is also accidental. this has happened to many coins before, and because it's unintentional, we can come to an agreement to correct the forked chain. there is a difference between an accidental 51% scenario, and a malicious one.

It would be almost impossible to maliciously attack the bitcoin blockchain, as the bitcoin network hashrate is 28,400,000 Ghash. https://blockchain.info/charts/hash-rate

Indeed I am talking about a malicious one, for the large enough pools, the network hashrate is irrelevant in case of a 51% attack. Truthfully, the fact that this is argued extensively in the forum and bitcoin wiki does not prevent such a possibility. It is known that a 30% hash power pool has also a serious chance to succeed in such an attack. From weaknesses section that you suggested, under "strong hash power attack" title;

A profit-seeking person will always gain more by just following the rules, and even someone trying to destroy the system will probably find other attacks more attractive. However, if this attack is successfully executed, it will be difficult or impossible to "untangle" the mess created -- any changes the attacker makes might become permanent.

Assuming a profit seeking person must be virtuous, and smart enough to be virtuous is simply utterly wrong. A profit seeker might also be stupid enough to do stupid things.The current solution by developers to a 51% attack is to warn miners to use alternative pools, and miners are known to be dumb and we can not blame to be not knowledgeable enough to educate themselves. Some pool owner may wish to just go out of the game and wish to kill the price so he may buy more, or apply a double spend attack with a so immense amount that sacrificing his long term gains to his short term gains might seem ok to them. You can not argue that, no pool operator would do that. For some reason, a pool operator or two may wish to do that and that is a problem. They should be able to wish, but should not technically be able to successfully perform such an attack. The value of your and our money should not be in their hands and can not rely on wishful thinking in such a case.

That above is the greatest current risk of bitcoin I believe and the fact that it did not happen can nowhere mean it won't. "Hopefully it does not happen", does not mean anything either as we are talking about a protocol decentralizing trust and yeah to the currently existing pool operator guys, you have to trust. 1 in a 1000 scenarios: "what if FBI gives money to the pool operator to kill bitcoin?" Would be much simpler than building their own 50% hash power farm ya? You think they wouldn't bribe? You believe that all pool operators will keep on the side of bitcoin? Think again.

I know Andreas Antonopolus gives speeches such as "we have our own measures to apply in case of a 51% attack" but I have nowhere seen him explaining exactly what they are gonna do after such an attack. I can not think of anything else than manually correcting blockchain. Indeed I like the guy, he is the man, seems highly rational and knowledgeable but it does not mean every word comin out his mouth is truth. He predicted that mtgox would come up alive and people would get 100% ROI when the goxcoin price went down to 200$, and he even tweeted about his prediction.

from your quote:

Quote

if i can't lock my house, then i wouldn't leave anything valuable in there. Similarly, i wouldn't put much value into a coin i could not secure.