Smart Contract with private data

Question

I'm looking for a way to have private data in an Ethereum smart contract. I explored the ZK space, could work on some scenarios but not totally private. I wanted to ask if you know new tools, sdks etc to make Ethereum smart contracts have private data inside them. Thanks

Answer 1

Zksync 2.0 is now highly compatible and Solidity-friendly in terms of porting smart contracts to zk roll-up applications, but I think a smart contract on the Layer-1 mainnet can never be made fully private unless its source code is made to appear encrypted and uncompile-able in the Etherscan "Contract" tab.

Perhaps zk roll-up privacy layers like Aztec Connect are home to projects that do enable private smart contracts within the Aztec network, not just private transactions, so Layer-2 only, most likely yes

Answer 2

I don't exactly know how do you want to store the private data. So I assume you want to do it in this way.

You have a an off-chain storage solution for the Ethereum network. The contract uses the SwarmAPI to store and retrieve private data in Swarm, The contract first hashes the data to be stored, and then uses the SwarmAPI to store the data. The contract then returns the data hash, which can be used to retrieve the data from Swarm at a later time.

here is the example code:

pragma solidity ^0.6.0;

import "https://github.com/ethereum/swarm/blob/develop/api/src/api.sol";

// The contract that stores private data
contract PrivateDataStorage {
    // The address of the Swarm API
    SwarmAPI api;

    // The function that stores private data in Swarm
    function storePrivateData(bytes memory data) public {
        // Hash the data to be stored
        bytes32 dataHash = keccak256(data);

        // Store the data in Swarm
        api.store(data);

        // Return the data hash
        return dataHash;
    }

    // The function that retrieves private data from Swarm
    function getPrivateData(bytes32 dataHash) public view returns (bytes memory) {
        // Retrieve the data from Swarm using the data hash
        return api.get(dataHash);
    }
}

This approach allows the contract to store private data off the blockchain, while only storing a hash of the data on the blockchain itself. This ensures that the data remains private, while still providing proof that it exists and has not been tampered with.

But, I don't if it's your want. Maybe you can show more code to have more discussion.