“Everything on the blockchain is public,” Aztec co-founder Joe Andrews told CoinDesk. “You need each node to be able to verify the state of another node and transactions. Everything needs to be public for that to occur. Aztec is effectively end-to-end encryption for those public messages. Instead of posting public transaction data, you post encrypted transaction data and the blockchain can still verify the correctness of that data using zero-knowledge proofs.”

https://www.coindesk.com/business/2021/12/16/ethereum-privacy-startup-aztec-raises-17m-in-paradigm-led-series-a/