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Author Topic: How random the last digit of a block hash really is?  (Read 9387 times)
CounterEntropy
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May 31, 2016, 10:20:02 AM
Merited by MarbleBoss (1)
 #1

I recently noticed a gambling website (www.bitcoinbetting.website https://www.chain-bet.com) is offering 4 times return on correctly guessing the last digit of a block hash. I would like to know, how random is the last digit of a block hash really is? Is there any bias towards numbers or letters?

Update: Lately, they have increased return to 10 times for each winning bet.
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dex1
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May 31, 2016, 11:39:30 AM
 #2

I recently noticed a gambling website (www.bitcoinbetting.website) is offering 4 times return on correctly guessing the last digit of a block hash. I would like to know, how random is the last digit of a block hash really is? Is there any bias towards numbers or letters?



It's a digit in hex format between 0 - F so in decimal between 0-15.
Your chance to guess the right digit is 1 in 16.



2c0de
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May 31, 2016, 12:06:35 PM
 #3

It is random as long miners/pools don't care about the site.

If the bets become bigger than subsidy (25BTC), it gets interesting.

Miners/pools can participate on site, rig future block digit to be zero, and sweep all unsuspecting user's funds who bet on 1.

OH and by the way, I know about system how truly fair betting can be constructed, but it's a secret Smiley

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CounterEntropy
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May 31, 2016, 10:32:33 PM
 #4

It's a digit in hex format between 0 - F so in decimal between 0-15.
I know. I asked about the randomness of its appearance as the last digit of a block hash. Whether increasing difficulty has any effect on it etc.

Your chance to guess the right digit is 1 in 16.
That's not always true for this specific game as the a player can chose multiple options at a time.

It is random as long miners/pools don't care about the site.

If the bets become bigger than subsidy (25BTC), it gets interesting.

Miners/pools can participate on site, rig future block digit to be zero, and sweep all unsuspecting user's funds who bet on 1.
I doubt if there is slightest truth in the bold part. Mining pools probably can not force the last digit of a block hash to be zero or any digit of their choice. It should depend on the nonce. Otherwise SHA would have been broken.
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May 31, 2016, 11:39:52 PM
 #5

Mining pools probably can not force the last digit of a block hash to be zero or any digit of their choice. It should depend on the nonce.
BREAKING NEWS: Forcing the hash is changing a nonce.

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June 01, 2016, 12:16:45 AM
 #6

In order for a miner to "pick" the last digit of the hash, they'd have to pass up a block subsidy plus a block's worth of transaction fees should the last digit of a qualifying hash (one that's low enough for the current difficulty) fail to match.

Passing up a chance to get a block subsidy is a pretty big deal.  Block subsidies are 25BTC at present, as someone said.  Soon though it will drop to 12.5BTC and miners may start withholding blocks if it looks like they could make more with the betting.

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June 01, 2016, 02:39:55 AM
 #7

I asked about the randomness of its appearance as the last digit of a block hash.

As long as the miner (or pool) doesn't have a significant incentive to ignore a successful block hash to continue trying additional nonce values for a different hash, it is random.

Whether increasing difficulty has any effect on it etc.

Difficulty has no effect on it.

Your chance to guess the right digit is 1 in 16.
That's not always true for this specific game as the a player can chose multiple options at a time.

You didn't explain what the options were.

You asked "how random is the last digit of a block hash really is".  The chance of guessing a single random last digit is 1 in 16 if miners (or pools) don't have a significant incentive to ignore a winning hash to continue trying additional nonce values for a different hash.

Mining pools probably can not force the last digit of a block hash to be zero or any digit of their choice. It should depend on the nonce. Otherwise SHA would have been broken.

Sure, but if the block reward is only 12.5 BTC (like it will be in about 7 weeks), and the prize for guessing the correct last hash digit is 200 BTC, then it might be worth it to the miner (or pool) to just ignore a successful hash and continue to try additional nonce values to see if the next successful block hash has a winning digit. They might miss out on the 12.5 BTC since they didn't broadcast their block, but 1 out of every 16 times they do it, they have a 6.25% chance of their next successful hash earning them 200 BTC.

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June 01, 2016, 02:53:40 PM
 #8

They might miss out on the 12.5 BTC since they didn't broadcast their block

They could always withhold the block until someone else finds a block, at which point they can broadcast their block and hope to win the race. They would still lose sometimes, but sometimes they'd win.

Buy & Hold
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June 02, 2016, 02:30:02 PM
 #9

 cat /tmp/hashlist | sed -e 's/\(^.*\)\(.$\)/\2/' | sort | uniq -c  | sort
  25530 9
  25640 5
  25707 8
  25792 4
  25807 b
  25849 a
  25877 6
  25882 0
  25897 f
  25904 e
  25923 d
  26025 7
  26084 3
  26169 c
  26176 1
  26217 2

looks random enough with 414479 blocks..
we need to check again in 100000 Blocks Smiley

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June 04, 2016, 07:04:20 PM
 #10

cat /tmp/hashlist | sed -e 's/\(^.*\)\(.$\)/\2/' | sort | uniq -c  | sort

Here it is in chart form - definitely random!
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June 07, 2016, 11:40:53 AM
 #11

cat /tmp/hashlist | sed -e 's/\(^.*\)\(.$\)/\2/' | sort | uniq -c  | sort

Here it is in chart form - definitely random!

Would have been kinda irritating if it wasnt random.
Since its SHA HASHING

CounterEntropy
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June 08, 2016, 09:46:53 PM
 #12

Mining pools probably can not force the last digit of a block hash to be zero or any digit of their choice. It should depend on the nonce.
BREAKING NEWS: Forcing the hash is changing a nonce.
Not sure if u r joking or spamming.

Mining pools probably can not force the last digit of a block hash to be zero or any digit of their choice. It should depend on the nonce. Otherwise SHA would have been broken.

Sure, but if the block reward is only 12.5 BTC (like it will be in about 7 weeks), and the prize for guessing the correct last hash digit is 200 BTC, then it might be worth it to the miner (or pool) to just ignore a successful hash and continue to try additional nonce values to see if the next successful block hash has a winning digit. They might miss out on the 12.5 BTC since they didn't broadcast their block, but 1 out of every 16 times they do it, they have a 6.25% chance of their next successful hash earning them 200 BTC.
Well, I think, there is no chance of this. Because, the highest amount of bet they are accepting against house is 0.1 BTC. So, the best amount that the miner can win for now is 0.8 BTC. No one will withhold 12.5 BTC for 0.8 BTC.
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June 08, 2016, 10:00:19 PM
 #13

Well, I think, there is no chance of this. Because, the highest amount of bet they are accepting against house is 0.1 BTC. So, the best amount that the miner can win for now is 0.8 BTC. No one will withhold 12.5 BTC for 0.8 BTC.

Interesting.  I wonder how they verify that a person isn't placing multiple bets (with multiple accounts)?

If the miner could set up 100 accounts and place 100 bets, then they could bet a total of 10 BTC to possibly win 80 BTC.

-ck
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June 08, 2016, 10:24:11 PM
 #14

They might miss out on the 12.5 BTC since they didn't broadcast their block

They could always withhold the block until someone else finds a block, at which point they can broadcast their block and hope to win the race. They would still lose sometimes, but sometimes they'd win.
They'd always lose if they broadcast it after another pool has found a block unless they were big enough to get two blocks back to back.

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June 08, 2016, 10:30:21 PM
 #15

They'd always lose if they broadcast it after another pool has found a block unless they were big enough to get two blocks back to back.

Not necessarily.

It would depend on how well connected they were to other miners and pools, and how well connected the pool that found the block was.

If they received the block directly from the pool that found it, and then immediately broadcast their own block to all the other pools before the competing block had propagated, then they'd have a pretty good chance of winning.

-ck
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June 08, 2016, 11:41:03 PM
 #16

They'd always lose if they broadcast it after another pool has found a block unless they were big enough to get two blocks back to back.

Not necessarily.

It would depend on how well connected they were to other miners and pools, and how well connected the pool that found the block was.

If they received the block directly from the pool that found it, and then immediately broadcast their own block to all the other pools before the competing block had propagated, then they'd have a pretty good chance of winning.
Anything's possible, sure, but since they have to receive it from the other pool and then broadcast their own, then every other pool may also have received the block. Sure they might be the only pool with a good connection to the one pool that solved the block but there is no magic to make one pool substantially better connected to all pools than all other pools might have. Too many ifs and buts, but yes in this pedantic world, my ALWAYS is indeed wrong. Let's say 99% to not leave any absolutes out there... Either way it's far too risky to likely lose a whole block reward.

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June 09, 2016, 01:54:35 AM
 #17

Normally a standard opinion would say 1 out of 16 but i would rebut in my experience its 1 out 99. But nevermind the hash, and consider this; if you make a certain roll and certain amount to match your roll number to that of the last hash digit then dont do it, theres a less chance youll get it and more btc wasted. But if you have just to guess it without making somebets then go on it doesnt matter if you make a guess as long as you dont lose a significant amount of btc.


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SKYFchain
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June 13, 2016, 09:33:45 PM
 #18

cat /tmp/hashlist | sed -e 's/\(^.*\)\(.$\)/\2/' | sort | uniq -c  | sort

Here it is in chart form - definitely random!

Seems to have a small sine-like wave pattern... Look how it "waves".

Obviously that would be smaller with a bigger sample.
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July 07, 2016, 11:51:11 AM
 #19

Normally a standard opinion would say 1 out of 16 but i would rebut in my experience its 1 out 99. But nevermind the hash, and consider this; if you make a certain roll and certain amount to match your roll number to that of the last hash digit then dont do it, theres a less chance youll get it and more btc wasted. But if you have just to guess it without making somebets then go on it doesnt matter if you make a guess as long as you dont lose a significant amount of btc.
They give u the option to bet on multiple options under a certain roll. So, the u have the choice to decide upon your winning probability.
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July 11, 2016, 06:47:14 PM
 #20

Hashes are uniformly distributed over the entire number space, so to answer you question, they are as random as they get. Furthermore, such hashes are routinely used in provably fair algorithms in other sites, sort of like an industry best practice.
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