Node.js Blockchain Implementation
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The speaker share his vision on the prospects of employing the technology for practical tasks. He presented basics of the blockchain architecture with case studies of JavaScript blockchain implementation using Node.js. This presentation by Valerii Radchenko (Senior Software Engineer, Consultant, GlobalLogic, Kharkiv) was delivered at GlobalLogic Kharkiv JS TechTalk #2 on August 17, 2018.
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Node.js Blockchain Implementation
- 2. Node.js Blockchain Implementation Valerii Radchenko JS TechTalk #2 17.08.2018
- 3. The Blockchain Wikipedia says: A blockchain, originally block chain, is a growing list of records, called blocks, which are linked using cryptography.
- 4. The Blockchain Wikipedia says: A blockchain, originally block chain, is a growing list of records, called blocks, which are linked using cryptography. The blockchain is a way of storing data for free access and making changes that are safe, confirmed by most users in an open distributed network.
- 5. Examples and tools • As an example, we will look at very simplified cryptocurrency implementation. • Tools and modules: - Node.js - Typescript - Crypto (Node.js core module) - Elliptic (npm package) - Base58, big-integer(npm package) - levelUp, levelDown (npm packages)
- 6. Agenda 1. Basic Concept 2. Persistence 3. Proof Of Work 4. Addresses 5. Transactions 6. Mining 7. More 8. Conclusion
- 8. Blocks • In blockchain, its blocks store valuable information. • Besides this, a block contains some technical information, like: - Version - Current timestamp - Its hash - Hash of the previous block
- 10. Block Hash • One of the important thing in a blockchain is calculating hashes. - It makes blockchain secure. - Calculating hashes requires some time even on powerful computers. - This is an intentional architectural design, which makes adding new blocks difficult, thus preventing their modification after they’re added.
- 12. Blockchain • Blockchain is a database structure: it’s an ordered, back-linked list. • Which means that blocks are stored in the insertion order and that each block is linked to the previous one. This structure allows to quickly get the latest block in a chain and to get a block by its hash.
- 13. Blockchain
- 14. Genesis block • In any blockchain, there must be at least one block. • The first block in the chain is called the genesis block and creating a blockchain must start by creating such block.
- 16. 16 Persistence
- 17. What kind of database fit our needs? • We need a simple serverless database to store our blocks one after another - NoSQL - Serverless - Key/value or documented - Simple and fast
- 18. Databases • LevelDB • LiteDB • VelocityDB • And many more…
- 19. BitcoinCore Database Structure • 'l' -> 4-byte file number: the last block file number used • 'c' + 32-byte transaction hash -> unspent transaction output record for that transaction • 32-byte block hash -> block record • The full database structure description
- 21. 21 Proof Of Work
- 22. Proof Of Work • A proof of work is a piece of data which is difficult (costly, time-consuming) to produce but easy for others to verify and which satisfies certain requirements. • Producing a proof of work can be a random process with low probability so that a lot of trial and error is required on average before a valid proof of work is generated.
- 23. Nonce and Complexity "Hello, world!0" => 1312af178c253f84028d480a6adc1e25e81caa44c749ec81976192e2ec934c64 "Hello, world!1" => e9afc424b79e4f6ab42d99c81156d3a17228d6e1eef4139be78e948a9332a7d8 "Hello, world!2" => ae37343a357a8297591625e7134cbea22f5928be8ca2a32aa475cf05fd4266b7 ... "Hello, world!4248" => 6e110d98b388e77e9c6f042ac6b497cec46660deef75a55ebc7cfdf65cc0b965 "Hello, world!4249" => c004190b822f1669cac8dc37e761cb73652e7832fb814565702245cf26ebb9e6 "Hello, world!4250" => 0000c3af42fc31103f1fdc0151fa747ff87349a4714df7cc52ea464e12dcd4e9
- 26. 26 Addresses
- 27. Bitcoin Address • 1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa This is the very first Bitcoin address • Addresses are not something that identifies you as the owner of a “wallet” • Address is a public key • In Bitcoin, your identity is a pair of private and public keys stored on your computer
- 29. Public-key Cryptography • Digital Signatures guarantee: - Data wasn’t modified while being transferred from a sender to a recipient - Data was created by a certain sender - The sender cannot deny sending the data • In order to sign data we need: - Data to sign - Private key • In order to verify a signature: - Data that was signed - The signature - Public key
- 33. 33 Demo Time
- 34. 34 Transactions
- 35. Transactions • No accounts • No balances • No addresses • No coins • No senders and receivers
- 38. Miners • Miners are nodes are run on powerful or specialized hardware (like ASIC), and their only goal is to mine new blocks as fast as possible. Miners are only possible in blockchains that use Proof-of-Work
- 39. The Coinbase Transaction • In Bitcoin, outputs come before inputs. • When a miner starts mining a block, it adds a coinbase transaction to it. A coinbase transaction is a special type of transactions, which doesn’t require previously existing outputs. It creates outputs out of nowhere.
- 41. • Every block must store at least one transaction and it’s no more possible to mine blocks without transactions. Storing Transactions in Blockchain
- 42. Change • Each output might be used only once. This means that once an input got a reference to an output the output cannot be used again even if its value is higher then needed to create a transaction. In this case, we create additional output in which value we place a difference between transaction amount and referenced output value. It is a change.
- 43. Unspent Transaction Outputs (Balance) • Unspent means that these outputs weren’t referenced in any inputs - tx0, output 1 - tx1, output 0 - tx3, output 0 - tx4, output 0 • When we check balance, we need only those that can be unlocked by the key we own.
- 45. Sending Coins • We want to send some coins to someone else. For this, we need to create a new transaction, put it in a block, and mine the block. • Before creating new outputs, we first have to find all unspent outputs and ensure that they store enough value.
- 46. The UTXO Set • Cause, we could have tons of blocks, we do not want to iterate through all of them. And UTXO Set can help us avoid this.
- 51. Merkle Tree • The full Bitcoin database (i.e., blockchain) takes more than 282 Gb of disk space • Because of the decentralized nature of Bitcoin, every node in the network must be independent and store a full copy of the blockchain
- 52. Merkle Tree And Simplified Payment Verification (SPV) • SPV is a light Bitcoin node that doesn’t download the whole blockchain and doesn’t verify blocks and transactions. Instead, it finds transactions in blocks (to verify payments) and is linked to a full node to retrieve just necessary data. This mechanism allows having multiple light wallet nodes with running just one full node.
- 55. 55 Mining
- 56. 56 Demo Time
- 57. 57 More…
- 58. Important things • Networking • Mining on GPU • Smart contracts (P2PKH)
- 59. 59 Conclusion
- 60. Conclusion • Node.js is a great platform for creating P2P networks, easy coding your blockchain applications and a big amount of various crypto functions. • But there are some cons: - Very slow mining performance - There is no ability to use GPU without workarounds
- 61. Helpful Links • BitcoinCore Wiki • Blockchain on Go • Bitcoin Explorer • GitHub ValeriyRadchenko
- 62. Thank you