Quote from: AnonyMint on November 28, 2013, 06:05:03 AM

Quote from: megastacks on November 28, 2013, 05:57:35 AM

Quote from: AnonyMint on November 28, 2013, 05:51:11 AM

Because mathematically you need to know the prior block hash before you can compute the next one.

And unless you have > 50% of the total network hash rate, then you can't permanently compute the next hash faster than the network can.

Note you can with declining probability P (< 1) compute the next hash faster than the network with less than 50% of the hash rate. Since probability is multiplicative, then doing this for two consecutive blocks is P x P, e.g. 0.1 x 0.1 = 0.01 so from 1 in 10 for one block rises to 1 in 100 chance for two blocks. Ditto for N consecutive blocks, e.g. for four blocks then 0.1 x 0.1 x 0.1 x 0.1 = 1 in 10,000 chance.

Anony, thanks for the explanation.

So if someone has over 50% of the total network hash rate is that something to be concerned about? Do you think it will ever happen?

My pleasure.

Yes very worried because it means they can control the network and even modify the protocol to make it a fiat, create a zillion coins, etc.. Some argue that they can't do that because the Bitcoiners will fork to a new chain. But these Bitards forget that the masses don't care about Bitcoiner idealism. They just want to buy their pizza. See my Transactions Withholding Attack thread for more explanation on that. Once the masses are already using one fork, they won't switch. The controller could run the fork well enough that the masses are happy, even while creating more coins, etc. Exactly like fiat. We go right back where we started.

In my (opinionated) analysis it is very likely to happen (when coin rewards diminish near to 0) with Bitcoin, because of a flaw in the design (transaction fees should be zero instead).

https://bitcointalk.org/index.php?topic=344154.msg3745513#msg3745513

https://bitcointalk.org/index.php?topic=342848.msg3745458#msg3745458

Or another attack which gives up control of the network. Dig, dig, dig into the rabbit hole:

https://bitcointalk.org/index.php?topic=349096.msg3744842#msg3744842

https://bitcointalk.org/index.php?topic=222998.msg3745278#msg3745278

https://bitcointalk.org/index.php?topic=336816.msg3745161#msg3745161

Alt coin users could transfer the value in their bitcoins to a more secure alt coin. The price of bitcoin would plummet but the price of the new coin would rise and we would continue using crypto coins just like we are doing with bitcoin.