Three architectural families have broken an assumption that was treated as a law of cloud architecture for two decades: that the machine running a computation must see the data the computation runs on. Homomorphic encryption operates on ciphertexts, secure multi-party computation distributes the work across non-colluding participants, and trusted execution environments isolate the work inside a hardware enclave opaque to the machine's owner. The privacy architecture of the next decade will be built on their compositions.