Post
Topic
Board Bitcoin Discussion
Re: SHA-256 (fixed: maybe) hacked, man gets away with 7 blocks in 10 minutes
by
QuantumMechanic
on 22/06/2011, 12:27:16 UTC
I ran some quick numbers. If I'm correctly understanding the distribution, once the first block was found, the chance of finding the next 6 blocks in that time window was something like 0.0000002. However, this possibility has existed every time a block has been found. The chance of this streak happening at least once in 132000 or so blocks is greater than 99.7%. In fact, there is a very high chance that his has happened more than once. If I find the time, I could do an analysis of the whole block chain to see if this has happened before.

Is there an easy way to extract block timestamps from the chain?
If you evaluated the cdf of a gamma distribution with parameters 7 and 1/10min at 10min to get 0.0000002, and 1 - the pdf of the binomial distribution with parameters 132000 and 0.0000002 evaluated at 0 to get 99.7%, then I think it's correct.  I'm too lazy to calculate it, though.

Also, http://www.xkcd.com/882/