We reuse all of the good ideas from Bitcoin and then we add this layer of
encryption so that the payment of Zcash from one user to the next is included in the
global replicated ledger for integrity (the recipient of the money can be sure that the payment has happened) and it's part of the
global consensus but it's encrypted so no one else can learn of your behaviour by looking at the ledger except for authorised parties who you have given the decryption
key to.