The multi-asset shielded pool (MASP) is a zero knowledge circuit that allows users to make transfers in a way that does not reveal the sender, receiver, or amount. Each transfer is a zero knowledge proof itself, and is often referred to as a "note". From the users perspective, the construction of these zero knowledge proofs occur behind the scenes.
The MASP is inspired by the work produced by the Electric Coin Company (ECC) who developed Zcash, and builds on the Sapling Circuit by implementing multi-asset functionality. In addition to the MASP, Namada has also implemented a zero knowledge circuit for rewarding privacy set contributions in a shielded manner. This circuit is called the Convert Circuit (CC for short).