CBGTBT - Part 4 - Mining
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A Complete Beginners Guide to Blockchain Technology Part 4 of 6. Slides from the #StartingBlock2015 tour by @blockstrap Part 1: http://www.slideshare.net/Blockstrap/cbgtbt-part-1-workshop-introduction-primer Part 2: http://www.slideshare.net/Blockstrap/02-blockchains-101 Part 3: http://www.slideshare.net/Blockstrap/03-transactions-101 Part 4: http://www.slideshare.net/Blockstrap/cbgtbt-part-4-mining Part 5: http://www.slideshare.net/Blockstrap/05-blockchains-102 Part 6: http://www.slideshare.net/Blockstrap/06-transactions-102
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CBGTBT - Part 4 - Mining
- 2. Introduction & Primer First, some context These slides are from the #StartingBlock2015 tour by @blockstrap. 6 European countries in 8 days – (Istanbul, Amsterdam, Barcelona, Prague, Berlin & London). We met lots of great people, answered lots of great questions and had a great time. We look forward to meeting many of them again in the near future. These slides might only make perfect sense if you were at the talks and can remember all the additional points we made whilst discussing the tech. This deck is 4th of 6. Questions? Comments? @MrAdamGiles adam@neuroware.io
- 3. Mining Refresher ➔ Transactions are broadcast to the network ➔ Blocks store records of transactions ➔ Blocks are created by Miners and then broadcast ➔ New blocks are added to the chain ➔ Miners then compete to build the next block
- 4. Mining So... ➔ Mining is the process of collecting transactions and ‘solving’ a block ➔ Blocks are immutable, we need to make sure they’re right ➔ We make solving a block hard and slow - maths to the rescue ➔ … but we want to make verifying a block easy ➔ Because we make mining hard, we reward miners… with bitcoin! ➔ Mining is the process of securing the blockchain
- 5. Mining Proof of Work ➔ All the transactions in the block are used to create the Merkle Root hash ➔ It’s added to the other metadata in the header, with a nonce ➔ We hash the whole thing, look at the resulting hash ➔ If it starts with a ‘0’ then we’ve solved the block, and broadcast it ➔ If not, we increment the nonce and try again ➔ Repeat until we find the leading zero
- 6. Mining Overly Simplified Example #!/usr/perl use Digest::SHA qw(sha256_hex); $last_block_hash = '5feceb66ffc86f38d952786c6d696c79c2dbc239dd4e91b46729d73a27fb57e9'; $tns = 'from:01234567890,to:354635406540654,Amount:100.00000000BTC'; $found_block = false; $nonce=0; while (false == $found_block){ $hash = sha256_hex($last_block_hash . $tns . $nonce); if("0" == substr($hash,0,1)){ $found_block=true; print 'Found!'; }else{ $nonce++; } }
- 8. Mining Easy Peasy Lemon Squeezy ➔ 11 attempts isn’t very many, we need to make it harder ➔ We introduce the concept of ‘difficulty’ ➔ Difficulty defines how many leading zeros when solving the block ➔ The more zeros we have find, the more attempts at hashing we need ➔ More hashing power becomes the driving force amongst miners
- 9. Mining Increasing the Difficulty ➔ As a way of controlling how hard it is to solve a block ➔ Can be adjusted to make it easier or harder ➔ Target time of 10mins per block ➔ As miners add hashing power to the network, we need to make it harder so increase the difficulty to compensate ➔ Difficulty is recalculated every 2016 blocks (approx 2 weeks)
- 11. Mining Crazy Increases in Difficulty
- 12. Mining It’s A Race ➔ Miners try to solve the block at the next height from the top of the chain ➔ The first to achieve it gets their block added to the chain ➔ All the other work done by the other miners is ‘wasted’ ➔ To create more blocks than other people, you’d have to have more hashing power than everyone else ➔ Current hashing power in the bitcoin network is more than the top 500 supercomputers combined
- 13. Mining Maintaining Blockchain Integrity Could someone with lots of hashing power control the blockchain? In theory, yes - simply compute blocks with double spend transactions & broadcast to the network But you need to control 50%+1 of the network for it to work reliably Network is currently at ~340 thousand terahashes per second That's 340,000,000,000,000,000 hashes per second!
- 14. Mining Too Much Math For One Man ➔ Club together in Mining Pools ➔ Each pool has many miners who split the problem up ➔ All members try to solve the same block in parallel ➔ Rewards are shared between the members
- 16. Mining Surviving miners have smaller %
- 17. Evolution of Mining Equipment
- 25. FPGAs Off the shelf HW Programmable chips Mining 2012 - 2013
- 28. 2013 Mining ASICs Custom Built HW Specialist Hashing chips
- 41. Why Bother? Mining You get paid! When you collect the transactions into a block, the miner inserts a special transaction at the beginning called a ‘coinbase’ transaction This ‘pays’ the miner for the work they did, and collects the transaction fees from all the transactions The coinbase value declines over time (halved every 4 years) This is the only way bitcoin is created - Only 21m btc will be created
- 42. Could You Fake A Block? Mining The hashing work you did ‘proof of work’ is easy to verify, a node will repeat the final hash you did to see if they get the same result as you. If not, the node won’t add the block to the blockchain The coinbase payment amount is based on an algorithm, if you fake it, the block is rejected If the block is rejected by the nodes, you don’t get any of the money you faked So… no, you can’t fake them!
- 43. Any Questions?
Notes de l'éditeur
- Assume familiar with software, just not blockchains Bitcoin can be polizing, quickly decends into conversations/arguments about politics, But as software is eating the workd, that's what we'll be focusing on Simplified first , then circle back round and dive deeper Simplifications can be missleading Tell meif too fast/slow