Smart Contract (Ethereum)

Put code in blockchain

• a special tx type
  • a program (a class object): “smart contract”
  • a special account
    • has address
    • can hold balance
    • can receive / initiate transfer
  • initialization execution
  • have permanent storage space
  • function triggered by transfer
• problem
  • avoid non-deterministic operation
    • external: trusted data sources
  • avoid computation and storage abuse: gas
  • isolation for safety

Application: Token systems

• token systems examples
  • reward points
  • new currency (coins)
  • shares
• a ledger
  • key variable: balances
  • key function: transfer
• ERC20: a template to set up a token system quickly

Application: stabilize price

• A and B both deposit in a smart contract 1000 eth, worth of X USD at the time
• after a pre-defined time period, return X-worth of eth to A and the rest to B