The advent of blockchain technology forces us to reconsider the upside and downside of public revelation of transactions and contracts. The implementation, application, and possible regulation of distributed ledgers involve choices that will critically affect information disclosure and economic interactions. Whether the ledger is public and permissionless, such as the Bitcoin or Ethereum blockchains, or private and permissioned, such as the Ripple or Hyperledger implementations, in principle transactions on a blockchain have a high native level of transparency. In this module, you will learn how privacy can can be protected in both public and private ledgers using both procedural and technological methods.