Before Nakamoto’s email all other solutions required a central authority of some kind. Banks and credit card companies like Visa or Mastercard deal with the problem by creating a central digital spreadsheet. Every time you pay for something on Amazon using my credit card, a number of dollars is taken out of the entry in that central spreadsheet – or ledger – next to my name and account number and is put next to Amazon’s name and account number on the same central spreadsheet. Before every purchase I make, the central system checks to see that there are sufficient funds next to my name,
...more
