DECO is a privacy-preserving oracle technology which uses zero knowledge proofs and allows data transmitted over the Internet to be confidentially attested to by oracles without the data being revealed to the public or to the oracle nodes themselves.
Sapphire is a confidential Smart Contract platform which enables smart contract execution the same as other networks, but with the added ability for those smart contracts to also be built in ways which can hide aspects of state.
There may be some overlap in the capabilities of these two technologies, but they are much more synergistic than competitive. DECO focuses on bridging off-chain data on-chain in a privacy preserving manner, while Sapphire’s use case is to enable on-chain smart contract execution which incorporates confidentiality. Just as DECO by itself is unable to come to consensus and execute a confidential smart contract, Sapphire by itself is also unable to use off-chain data without an Oracle. Privacy is becoming a major theme in crypto recently and we are excited to see so many protocols being developed which share the Oasis vision of a responsible data economy.