Quote from: monsterer on March 19, 2016, 10:53:44 AM

Quote from: jl777 on March 19, 2016, 12:26:03 AM

and the hashrate was a small fraction back around block 225K. Not sure, but I think it is harder to reorg now vs then?

It was the same then as it is now - back then, network power was less than it is now, so although difficulty was lower than it is now, blocks were still 10 minutes each.

Sure, theoretically, but I dont like to just assume that the theory is precisely followed by reality.

My concern is with the practical. When did the ASIC's come out? That is a nonlinear increase in hashrate per amount of capital.

Moving forward is it likely to have the same hashrate improvements was was possible a couple years ago. Not sure on the state of ASIC geometries, but if already the smallest practical geometry is being used, then it cant really get much more cost effective. Larger, yes, but with proportional cost for the silicon. Cleverer, yes, but possibly most of the low hanging fruit is already done

Not sure the state of mining at block 225K, but given those factors it is possible that things are still exactly the same, but I am skeptical about that. What are the currently envisioned improvements in hashrate efficiency?

Actually instead of just guessing, lets look at https://blockchain.info/charts/hash-rate?timespan=all&showDataPoints=false&daysAverageString=1&show_header=true&scale=0&address=

the alltime chart shows a definite slowdown of hashrate increase, so that does not seem the same to me. Granted from one block to the next, not much changes, but the discontinuity of new tech is what would create the temporary ability for a bigger reorg.

01/01/2010 18:15:05,0.006997468320659102
01/01/2011 18:15:05,128.16206770778084 18315x 2010
01/01/2012 18:15:05,8591.40080069935 67x 2011
01/01/2013 18:15:05,24291.440498714688 2.82x 2012
01/01/2014 18:15:05,11740802.089632047 483x 2013
01/01/2015 18:15:05,335365290.0920246 28.56x 2014
01/01/2016 18:15:05,697129166.4058079 2x 2015

As things went from CPU -> GPU -> FPGA -> ASIC and as market price is changing dramatically we see the change in hashrate vary from 18315x to 2x, so it does not seem safe to assume that things are the same. The 2014 gain was probably skewed by the bull market peak price bringing in a lot of new capital, but maybe that is around the same time ASIC made a big leap?

The most likely way for an attack against bitcoin PoW seems to me for the creator of advanced tech to have a disproportionate hashrate per capital available, especially when efficiency gains are measured in the orders of magnitude. However, once the orders of magnitude technology gains are already done, it becomes a matter of much more "incremental" improvements of doubling per year.

At least that is what I had guessed and the numbers indicate something similar to that. One way to look at this is back in 2013 what was the likelihood of a 500x hashrate increase? Was it really such a remote possibility? And what is the chance of a 500x hashrate increase now?

Is there really any chance that next year we see 1,122,825 * 500 terahashes? or even 10x.
Yes I know the difficulty adjusts, but that is every 2016 blocks, there is a window of time where a technical leap increases the chance of larger reorg, but as time passes I think this chance is less and less.

James