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  • Sean> How do Bitcoin miners mine?

  • Mike> There's no actual digging involved. Think back to

  • our video on hashing - so a hash function takes a message of any length and

  • returns a fixed length hash which hopefully looks quite random right so if

  • you change even a little bit of your message the whole hash changes, so this

  • is how Bitcoin mining works right in brief... So we have a block and at the top

  • of the block is the hash of the previous block and a number right which we're

  • going to call our nonce this is a number we're making up let's start at 1 and go

  • up and then here we've got all the transactions so transactions - one of

  • which will give me some bitcoins because I'm the miner. The way this works is I

  • start with a random number here and then I hash this entire thing and I get a

  • hash out the bottom here. To mine successfully this hash needs to be very

  • very small so let's say for example it has ten leading zeros as an example if I

  • successfully pick a number where when I hash this entire thing including the

  • number it has ten leading zeros I've successfully mined that Bitcoin. Now

  • that's quite unlikely you've got to think that each zero & one has a roughly

  • 50% chance of being a one so to get one leading zero it's going to be about 50%

  • of the time two leading zeros about 25% of the time and so on the more leading

  • zeros we require the harder this process is. So it doesn't happen yeah the first

  • time I pick a one I hash it and it doesn't work so what I do is I go to 2

  • and I hash it again and I get a totally different hash which maybe has a

  • different number of leading zeroes and I go "does this does this work?" no, ok so 3, 4

  • 5, 6, 7, 8, 9, 10 and so on and I just keep churning away with these random numbers

  • in this "nonce" field here incorporating any transactions I've received in the

  • meantime until I get this kind of golden hash that I've been looking for which is

  • very very small so lets say 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 some

  • numbers say 1 0 1 1 and something like that right now

  • this is sha-256 in the case of Bitcoin so it's 256 bits long now as soon as I've

  • done that I go well brilliant I've got some bitcoins i transmit this to the

  • network and everyone sees this and goes cool and then they take this hash and

  • they put it in the next block and start mining on that one as well with new

  • random numbers so every time someone stumbles across a

  • hash which is small enough that's when they've mined the Bitcoin right and so

  • that's how the difficulty of a network is changed - you just change the

  • threshold of number of zeros or size of your hash that you need to be below in

  • order to be successful every couple of thousand blocks the network will look

  • at how long it took and if like a bunch more miners have appeared so it's

  • actually starting to get a little bit too easy they'll they'll increase this

  • difficulty such that hopefully a Bitcoin is mined

  • roughly every ten minutes now of course this process is random so

  • it might be less, might be more but on average... If a bunch of miners

  • disappeared suddenly it's taking 50 minutes to mine a

  • Bitcoin (Block?) they'll just reduce this threshold so that you can mine that

  • little bit more easily. The number of bitcoins that a miner is awarded is halved

  • every so often as well - so I think is it at 12.5 at the moment so I will have

  • sort of plus 12.5 for Mike in here as sort of my benefit of being the miner so

  • this will only ever get actually put into the blockchain if I'm the one that

  • finds this hash otherwise unfortunately it'll be someone else's name in here

  • Sean> we've sat here and watched Beast churn through billions of password hashes -

  • How hard can it be to come up with this number?

  • Mike> As hard as they need it to be

  • you've got to think that for all the miners on earth at least a lot of them

  • have got dedicated hardware many trillions of hashes and they're still

  • only doing it every 10 minutes right it's not easy to do

  • and they can just keep making this more difficult until it takes about ten

  • minutes. In some ways you can't make the problem more easy by buying more and

  • more hardware because it will just make itself more difficult for you.

  • For now most of my contact with it is via a terminal and I ask it to do things it

  • does them very, very fast. This particular server has four Titan X graphics cards

  • in it a Titan X is one of the foremost graphics cards there are new....

Sean> How do Bitcoin miners mine?

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B2 hash leading miner bitcoins mined block

Bitcoin Mining in 4 Minutes - Computerphile

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    林宜悉 posted on 2020/04/04
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