Ethereum developer barry has announced new progress on zkEVM private smart contracts: it supports private user states but does not have private global states.

Jinse Finance reports that Ethereum developer barryWhiteHat stated that with the commercialization of the zk-SNARKs Virtual Machine (zkEVM), an interesting opportunity has emerged: it can provide private smart contract infrastructure while maintaining compatibility with the Ethereum Virtual Machine (EVM). Developers can write Solidity code and compile it using a specific version of the Solidity compiler or some post-processing tools to create private smart contracts. There are some important trade-offs surrounding private global state and privacy, primarily because: to prove something, one must know what they are proving. Therefore, there cannot exist such a private smart contract - one that has a global public state that you are not aware of. It follows that there cannot exist a private smart contract with a global private state. For example, applications like Uniswap cannot be implemented in a private manner because the prover needs to know the balances of the two liquidity pools in order to prove that a swap transaction is executed correctly. Therefore, some applications that we are familiar with and favor cannot currently be implemented in a private form unless we have input-output (IO) functionality — this is precisely why IO is critical. It allows us to build a completely private Ethereum, and its trust assumptions are entirely consistent with those of native Ethereum. However, this article aims to explore how to implement a private smart contract by adding the two opcodes pstore and pload in reth and compiling it into the zk-SNARKs Virtual Machine, which has a private user state but does not have a private global state.