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Author Topic: Someone explain?  (Read 168 times)
DrSha
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February 12, 2018, 12:35:21 AM
Merited by DannyHamilton (2), mprep (1)
 #1

I want to know how this can be possible in mining when it's a random process..
For a single pool to hit consecutive blocks back2back like this the odds are astronomical...


Code:
508737 BTC.com 4 minutes ago 987.7 kB
508736 BTC.com 14 minutes ago 963.6 kB
508735 BTC.com 38 minutes ago 972.1 kB
508734 BTC.com 56 minutes ago 971.7 kB
508733 BTC.com 1 hour 18 minutes ago 980.6 kB
508732 BTC.com 1 hour 34 minutes ago 994.0 kB
508731 BTC.com 1 hour 37 minutes ago 965.9 kB

Before the answer is just "a lot of hashrate" I do not think this is only luck or hashrate,

last 24hrs btc.com network hashrate jumped from 24.9% to 31.5%

https://blockchain.info/pools?timespan=48hours
https://blockchain.info/pools?timespan=24hours

I though mining was random 7 block back2back strange?


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February 12, 2018, 01:31:41 AM
 #2

For a pool like BTC.com that has such a large portion of the hashrate, eventually hitting 7 blocks in a row is honestly not that unlikely. There are lots of blocks every day, so they have plenty of chances to hit a few in a row like that.

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February 12, 2018, 01:35:51 AM
Merited by DannyHamilton (2), LoyceV (1)
 #3

With a hashrate of 31.5%, the chance of mining the next six blocks in a row after mining the first one is just under 1 in 1000. And given that on average 144 blocks are mined every day, this sort of coincidence can be expected to occur about once a week. Even highly unlikely events are bound to occur eventually given enough time.

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February 12, 2018, 01:38:25 AM
 #4



 when mining solo, this is typically impossible, but with a pool who know what they are doing, its possible, chances are limited but its possible depending on the complexity of the block.
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February 12, 2018, 02:51:37 AM
 #5

A streak like this (7 blocks in a row by the same pool with 25% of the global hashrate) statistically happens on average every 500 hours.
So roughly every month.

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February 12, 2018, 04:05:31 AM
Merited by DannyHamilton (2), mprep (1), pedrog (1), ranochigo (1), LoyceV (1)
 #6

Satoshi even mentioned this in his whitepaper https://bitcoin.org/bitcoin.pdf Wink
See page 8 where it states:
"q=0.3
z=0     P=1.0000000
z=5     P=0.1773523
z=10   P=0.0416605
"

that means those control 30% hashrate (q=0.3) can mine 5 consequent blocks (z=5) by 17% probability and even can mine 10 consecutive blocks (z=10) by 4%. so, your reported case of a z=7 consequent block can happen sometimes.

Your surprise is legit as it is widely assumed that no one would control more than 10% of the hashrate so 6 confirmation is sufficient. But, currently this is not the case and if you refer what satoshi suggested for such a case is :
"P < 0.001
q=0.10 z=5
q=0.15 z=8
q=0.20 z=11
q=0.25 z=15
q=0.30 z=24
"
which means if there is an entity with 30% of hashrate, a transaction is safe from double spending (its probability is less than 0.1% ) after 24 confirmations (z=24).

You are right to be surprised as "the mining pools" breaks the original bitcoin philosophy.

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February 15, 2018, 01:57:16 PM
 #7

A streak like this (7 blocks in a row by the same pool with 25% of the global hashrate) statistically happens on average every 500 hours.
So roughly every month.
Sorry for late reply.

So this is not withholding block finds and broadcasting the transactions one after the other?

Code:
509287 BTC.com 4 hours 1 minute ago 992.479 kB
509286 BTC.com 4 hours 5 minutes ago 975.617 kB
509285 Unknown 4 hours 17 minutes ago 989.775 kB
509284 BTC.com 4 hours 21 minutes ago 958.236 kB
509283 BTC.com 4 hours 26 minutes ago 973.774 kB
509283 BTC.com 4 hours 29 minutes ago 973.774 kB
509282 DiscusFish / F2Pool 4 hours 43 minutes ago 950.709 kB
509281 BTC.TOP 4 hours 58 minutes ago 955.183 kB
509280 BTC.com 5 hours 13 minutes ago                 834.699 kB
509279 AntPool 5 hours 15 minutes ago 935.087 kB
509278 BTC.com 5 hours 19 minutes ago 0.241 kB
509277 BTC.com 5 hours 19 minutes ago 981.321 kB
509276 BTC.com 5 hours 29 minutes ago 986.026 kB
509275 BTC.com 5 hours 33 minutes ago 951.054 kB
509274 BTC.com 5 hours 53 minutes ago 965.622 kB

They seemed to scaleback to 22% for fewdays then back to 30% today for the jackpot rolls.  This is beyond luck or chance.

https://statoshi.info/dashboard/db/blocks?from=1518674293323&to=1518679831784

  BTC.com    46    30.87%  ,<---gain %
  AntPool    25    16.78%  ,<---lost %
  BTC.TOP    17    11.41%  ,<---lost %

antpool lost hashrate..as did btc.top then we see the jackpot streak again.

https://statoshi.info/dashboard/db/mining?from=1518685211469&to=1518706811469

and again
Code:
509309 BTC.com 1 hour 18 minutes ago 975.4 kB
509308 BTC.com 1 hour 23 minutes ago 975.8 kB
509307 BTC.com 1 hour 35 minutes ago          994.1 kB

and later...again.. x2 lots of 3 blocks... split apart by hash shufflers ...

Code:
509316 BTC.com 7 minutes ago 967.5 kB
509315 BTC.com 23 minutes ago 974.0 kB
509314 BTC.com 1 hour 1 minute ago 993.7 kB
509313 AntPool 1 hour 3 minutes ago 980.2 kB
509312 BTC.TOP 1 hour 13 minutes ago 967.0 kB
509311 AntPool 1 hour 23 minutes ago 918.1 kB
509310 AntPool 1 hour 27 minutes ago 982.4 kB
509309 BTC.com 1 hour 33 minutes ago 975.4 kB
509308 BTC.com 1 hour 38 minutes ago 975.8 kB
509307 BTC.com 1 hour 50 minutes ago 994.1 kB

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February 15, 2018, 03:18:49 PM
Merited by DrSha (1)
 #8

So this is not withholding block finds and broadcasting the transactions one after the other?

It doesn't seem to be, but it would be difficult to know for certain. If it can be demonstrated that this orphaned other blocks, that might increase the suspicion, but even then it would be difficult to prove with any certainty that it was any type of bock withholding attack.

They seemed to scaleback to 22% for fewdays

Or, they just got less lucky for a few days?

then back to 30% today

Or, just got a bit luckier today?

for the jackpot rolls.

What are "jackpot rolls"?

This is beyond luck or chance.

It looks perfectly normal to me.

 BTC.com    46    30.87%  ,<---gain %
  AntPool    25    16.78%  ,<---lost %
  BTC.TOP    17    11.41%  ,<---lost %

antpool lost hashrate..as did btc.top then we see the jackpot streak again.

You've got that backwards...

It is impossible to know what the hashrate of those pools is.  What we DO know is how many blocks they admitted to adding to the blockchain.

The ESTIMATED HASHRATE is calculated by counting the blocks that are solved and the speed at which they are solved.  So, when they solve more blocks, it increases the ESTIMATE of their hash rate.  When they solve less blocks, it decreases the ESTIMATE of their hash rate.

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February 15, 2018, 03:32:19 PM
 #9

I was thinking they could be sharing hash rate or switching hashrate to and from each pool depending on luck?

Lets say 3 pools each with following hashrate.
pool A 100ph
pool B 200ph
pool C 300ph

Pool A finds block. pool A then moves 25ph to pool B Pool B now has 225ph pool B now finds few blocks luck change. Pool B now move 50ph to pool C pool C then mine multiple blocks luck -% all pools restart process.

If you watch the network hashrate you can clearly see large portions coming online and offline.

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February 15, 2018, 03:50:24 PM
 #10

If you watch the network hashrate you can clearly see large portions coming online and offline.

Like Danny said, there is no way to watch the actual hashrate of the network. You can only observe how many blocks they have mined, and estimate their hashrate from that information.

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February 15, 2018, 04:00:11 PM
 #11

I was thinking they could be sharing hash rate or switching hashrate to and from each pool depending on luck?

Lets say 3 pools each with following hashrate.
pool A 100ph
pool B 200ph
pool C 300ph

Pool A finds block. pool A then moves 25ph to pool B Pool B now has 225ph pool B now finds few blocks luck change. Pool B now move 50ph to pool C pool C then mine multiple blocks luck -% all pools restart process.

This wouldn't accomplish anything useful. It doesn't change the total amount of hashrate that the combined pools have (600ph).

If you watch the network hashrate you can clearly see large portions coming online and offline.

It is not possible to "watch the network hashrate".  All you can do is watch the block completion rate.  Then you can use the block completion rate to ESTIMATE a hash rate.  If mining is lucky and some blocks happen faster than average, then the ESTIMATE of the hash rate will increase (since the estimate is based on the block creation rate).  If mining is unlucky and some blocks happen slower than average, then the ESTIMATE of the hash rate will decrease (since the estimate is based on the block creation rate).

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February 15, 2018, 04:03:15 PM
 #12

I was thinking they could be sharing hash rate or switching hashrate to and from each pool depending on luck?

Lets say 3 pools each with following hashrate.
pool A 100ph
pool B 200ph
pool C 300ph

Pool A finds block. pool A then moves 25ph to pool B Pool B now has 225ph pool B now finds few blocks luck change. Pool B now move 50ph to pool C pool C then mine multiple blocks luck -% all pools restart process.

If you watch the network hashrate you can clearly see large portions coming online and offline.

Some people will change poola based on prospective earnings yes. Per pool, an API call can normally be used to find the total hashrate and the amount of blocks mined by that pool in the last x amount of time (anywhere from 2 hours to a week or so as some smaller mining pools may find a block only every week or so but it may work out that everyone gets a better share, profit wise). There's an argument for that not making a lot of a difference though calculation wise.

There are other factors though. A company with some miners in it (separate from what the company already does) may just leave the miners running for 9 or 10 hours a day for example. Or someone may live in a flat with electricity already paid for and may turn the miner off at night to sleep in a room a bit quieter.

And hobbyistic miners that won't ROI with their miners may only leave them running for an hour or two every so often. If people do this at different times (due to timezone differences) then the mining share to a certain pool may increase - like a solo mining pool if someone feels particularly lucky.


Also, in the OP. I see btc.com being mentioned. That pool is owned by bitmaintech who also own antpool.com and have a large amount of hashing servers and server farms.

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February 15, 2018, 04:05:03 PM
 #13


It doesn't seem to be, but it would be difficult to know for certain. If it can be demonstrated that this orphaned other blocks, that might increase the suspicion, but even then it would be difficult to prove with any certainty that it was any type of bock withholding attack.

Would it be fair to say that "technically" it would be possible and block withholding should be classed as attack or exploit should bitcoin not look to implement something like MBBM (must be broadcast message) to coin base transaction to stop block withholding seems very unfair there is even a way to do this in the current system and that there seems to be little or no talk on detection of unfair play in the space.

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