Privacy Token

The project developed a universal ERC20privacy contract based on the Oasis Sapphire privacy library to achieve balance encryption and private transfers. It provides a signature authorization interface based on EIP-712 to complete token transactions without leaving traces on-chain.

Overview

• Balance Privacy: The contract internally encrypts and stores balances. Normal queries only return data visible to the user themselves.
• Signature Authorization: Supports EIP-712 based VIEW / TRANSFER / APPROVE permissions, avoiding the exposure of sensitive authorization details on-chain.
• No Event Logs: Does not record event logs, preventing token transaction traces on the blockchain.
• Anti-Replay: Uniqueness verification of signatures and expiration time limits prevent reuse.
• Wrap/Unwrap: Can be wrapped/unwrapped with the base ERC20, making it compatible with external liquidity.
• Token Deposit/Withdraw: Native tokens like sapphire testnet (TEST) can directly use this interfaces.

After deploying the ERC20privacy contract, the ERC20 token can be wrapped into an ERC20privacy token through the wrap and unwrap interfaces, thus realizing the minting of privacy tokens.

Note: Each ERC20privacy token can only correspond to one ERC20 token.

Network and Contract Deployment (Mainnet/Testnet)

• EMC: The token of the Evidence Market project.
• EMC.Privacy: The ERC20privacy token of EMC.
• wROSE.Privacy: The ERC20privacy token of wROSE.

Project	Mainnet	Testnet
Network Name	Oasis Sapphire	Oasis Sapphire Testnet
Chain ID	23294	23295
EMC	TBD	0x990DE401CD0103a0107D27F82283db60F4844203
EMC.Privacy	TBD	0x449e2CD61F0328Ae68f4A530170C892B45b4B269
wROSE.Privacy	TBD	0x4e30337908E19917f3F74adB45966114A55205c2

Example of EIP-712 Key Structure

// EIP-712 domain parameters
bytes32 private constant EIP712_DOMAIN_TYPEHASH = keccak256(
    "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
);
bytes32 public immutable DOMAIN_SEPARATOR;

bytes32 public constant EIP_PERMIT_TYPEHASH = keccak256(
    "EIP712Permit(uint8 label,address owner,address spender,uint256 amount,uint256 deadline)"
);

enum PermitLabel { VIEW, TRANSFER, APPROVE }

struct EIP712Permit {
    PermitLabel label;
    address owner;
    address spender;
    uint256 amount;
    uint256 deadline;
    SignatureRSV signature;
}