为何选择区块链?

class VirtualBank:
  def deposit(sender, amount):
    # transfer amount from sender to myself (the bank)
    # do internal bookkeeping to credit the sender

  def withdraw(sender, amount):
    # ensure the sender had enough on deposit
    # do internal bookkeeping to debit the sender
    # transfer amount from myself (the bank) to sender

  def borrow(sender, amount):
    # ...

  def repay(sender, amount);
    # ...