Chapter 6. The blockchain

This chapter covers

  • Improving spreadsheet security
  • Lightweight (SPV) wallets
  • Reducing wallet bandwidth requirements

In chapter 5, we discussed transactions that let anyone verify all transactions in the spreadsheet. But there are still things verifiers can’t verify—that Lisa doesn’t remove or censor transactions. We’ll handle censorship resistance in chapters 7 and 8. This chapter examines how to make it impossible for Lisa to remove or replace transactions without also making it obvious that she’s tampered with the transaction history.

Lisa does this by replacing the spreadsheet with a blockchain (figure 6.1). The blockchain contains transactions that are secured from tampering through hashing and signing the set ...

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