Privacy on Ethereum is being actively worked on by a number of different teams.
- Zero Knowledge-based
- zk-SNARKs (used in Zcash)
- zk-STARKs
Aztec Protocol is building an efficient zero-knowledge privacy protocol and decentralised exchange. The protocol is already live on Ethereums mainnet.
Starkware Industries is using STARK technology to improve scalability and privacy on Ethereum.
Enigma Protocol are building 'secret contracts' which enable computation over encrypted data.