Building Confidential Tokens ​
ERC-7984 is a confidential fungible token standard designed from the ground up with privacy in mind. Unlike ERC-20, where balances and transfer amounts are visible on-chain, ERC-7984 stores everything as encrypted handles. Only authorized parties can decrypt the actual values.
The @iexec-nox/nox-confidential-contracts library provides a ready-to-use ERC7984 base contract, similar to how OpenZeppelin provides ERC20. You inherit from it and add your own logic (minting, burning, access control).
ERC-7984 vs ERC-20 ​
| Feature | ERC-20 | ERC-7984 |
|---|---|---|
| Balances | Public uint256 | Encrypted euint256 |
| Transfer amounts | Public | Encrypted |
| Total supply | Public | Encrypted |
| Approval mechanism | Allowances | Time-bound operators |
| Callbacks | No (ERC-1363) | Built-in (transferAndCall) |
| Addresses | Public | Public (confidentiality, not anonymity) |
Key Concepts ​
Encrypted handles ​
Balances and amounts are not stored as plain numbers. They are stored as euint256 handles: 32-byte references to encrypted data managed by the Nox protocol. All arithmetic on these values happens off-chain inside a TEE.
Operators (not allowances) ​
ERC-7984 replaces the ERC-20 approve/transferFrom pattern with operators. An operator can move any amount of tokens on behalf of a holder until a timestamp. This is simpler and avoids the well-known ERC-20 approval front-running issue.
All-or-nothing transfers ​
Transfers never revert on insufficient balance. Instead, the contract uses Nox.safeSub() internally: if the sender does not have enough tokens, the transfer silently succeeds with zero tokens moved. This prevents leaking balance information through transaction reverts.
Callbacks ​
ERC-7984 has built-in transferAndCall support (inspired by ERC-1363). When transferring to a smart contract, the recipient's onConfidentialTransferReceived hook is called. If the callback returns false (encrypted), the transfer is automatically refunded.
What You'll Learn ​
- How to create ERC-7984 compliant tokens
- How to wrap existing ERC20 tokens
- How to build token swap applications
- Best practices for confidential token design
Next Steps ​
- ERC7984 Token - Create native confidential tokens
- ERC20 to ERC7984 - Wrap existing ERC20 tokens
- Live Demo - Explore a live application showcasing confidential tokens