Skip to content

Latest commit

 

History

History
116 lines (103 loc) · 3.29 KB

README.MD

File metadata and controls

116 lines (103 loc) · 3.29 KB

Blockchain

Overview

  • distributed and decentralized legder
  • store data
  • publicly shared access all nodes of its network
  • block
    • data: [A -> B $30, B -> C $10]
    • metadata: create time, position
    • hash: current block data + meta data + previous hash
    • reference from current block to previous block
  • ledger
    • record-keeping book store all transactions of an organization
    • distributed ledger for all nodes
    • update the ledger boardcast to block chain network
  • centralized vs decentralized
    • centralized
      • powers
      • full authority to fine or reward
      • complete trust with entity
    • decentralized
      • every records data
      • fair and transparent system
      • trustless
  • why blockchain
    • lead to trustless system
    • no middle men
    • no central point of failure

Cryptocurrency

  • digital medium of exchange

  • use cryptography to generate digital signature

  • digital signature

    • private key <- owner
      • encrypt (original data + new data) = signature
    • public key <- every one
      • decrypt signature = (original data' + new data')
      • compare original data to original data'

  • wallets

    • store private and public key
    • public key is address of wallet, others send cryptocurrency to owner
    • sign the transaction

  • Mining

    • transaction are temporarily "unconfirmed"
    • include blocks of transactions by solving a "proof of work" algorithm
      • difficult to solve, computationally expensive
      • once solved, miner can add block and miners will verify
      • miners are rewarded for adding block to chain
      • difficulty can adjust to control the rate of new blocks coming in
    • longer blocks
    • hash validation

  • Bitcoin

    • decentralized cryptocurrency in 2009
    • growth, widespread adoption
    • white paper

  • Use Case

    • voting
    • documentation and identification system

Block

  • timestamp
  • lastHash - the hash of block before
  • hash - based on its own data
  • the data to store
  • genesis block
    • first block with dummy value
  • Hash Algo: SHA-256
    • 32 byte (256bit) for unique data input
    • one-way hash
    • block verification

Proof of Work System

  • do computional work to add block
  • Hashcash was a proof-of-work
  • expensive to generate corrupt block
  • difficulty = 6, Hash with leading 6 '0'
  • nonce value adjusts in order to generate new hashes
  • 51% Attack a dishonest miner has more than at least 51% of the network's power

Wallet

  • store the balance of an individual
  • store
    • private key: sign the private signature
    • public key: verify the signature and public address
  • transactions
    • input: sender's balance and public key
    • output:
      • receipt address, amount received
      • sender address, balance
  • digital signatures
    • private key + transaction data = signature
    • public key decrypt signature and verify data
  • components
    • wallet
    • digital signature and verification
    • transaction object
  • node
    • sync chain
    • broadcast transaction

Miners of Transaction

  • take transaction from pool and store into block
  • miner received rewards for mining
  • transaction go from "unconfirmed" in the pool to "confirmed" in the chain