How to Implement a Secure Delegated Signing Authority Model

Delegated signing authority is a design pattern that allows one entity, the delegate, to execute transactions on behalf of another, the principal, without holding their private keys. This is essential for creating seamless user experiences in dApps, enabling features like gasless transactions, automated strategies, and session keys. Unlike simple multi-signature wallets, delegated models often involve pre-authorizing specific actions for a limited time or value, reducing the principal's exposure to risk. The core challenge is implementing this delegation securely, ensuring the delegate cannot exceed their granted permissions.

The foundation of any secure implementation is a smart contract that acts as the authority manager. This contract holds the logic that validates whether a requested action falls within the delegate's pre-approved scope. A standard approach uses a signed EIP-712 typed structured data message from the principal. This message, or "permit," explicitly defines the delegation parameters: the delegate address, a valueLimit (e.g., 1 ETH), a timeLimit (e.g., 1 week), and the targetContract and functionSelector they are allowed to call. The contract stores this authorization and checks it against every execution request.

Here is a simplified Solidity example of the core verification logic in an authority manager contract:

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function executeWithAuth(
    bytes32 permitHash,
    address target,
    bytes calldata data
) external {
    Authorization storage auth = authorizations[permitHash];
    require(auth.delegate == msg.sender, "Not authorized delegate");
    require(block.timestamp <= auth.validUntil, "Authorization expired");
    require(target == auth.allowedTarget, "Target not permitted");
    // Execute the call
    (bool success, ) = target.call(data);
    require(success, "Call failed");
}

The permitHash is the EIP-712 hash of the signed delegation message, which the contract uses to look up the stored permissions.

Security considerations are paramount. Implementers must guard against replay attacks by using nonces or unique permit hashes. Permission scoping should be as narrow as possible; avoid granting blanket approval to call any function. Consider integrating with established standards like ERC-2771 for meta-transactions or ERC-4337 account abstraction, which provide robust frameworks for delegated execution. Regularly audit the logic that maps function selectors to allowed actions, as this is a common attack vector. For high-value systems, combine delegation with multi-signature requirements or time-delayed revocations.

Real-world use cases demonstrate the pattern's utility. In DeFi, a user can delegate a bot to harvest and compound yield up to a certain amount per day. In gaming, a player can grant a session key limited rights to interact with a game contract for the duration of their play session. To implement, start by defining the exact permissions your application needs, then use libraries like OpenZeppelin's EIP712 and SignatureChecker to handle the cryptographic verification. Always test thoroughly on a testnet, simulating edge cases where a delegate tries to exceed their limits.

A delegated signing authority model allows a primary account (e.g., a multisig wallet or a user's cold wallet) to authorize a secondary, often more accessible, account to sign specific transactions on its behalf. This pattern is fundamental to smart contract wallets, gas abstraction, and secure automation. The core challenge is enabling this delegation without compromising the security of the primary account's private keys. Implementation typically involves three components: a delegation smart contract that holds the authorization logic, a signature verification standard like EIP-712 for structured data, and an off-chain agent that crafts and submits authorized transactions.

Before writing any code, you must define the authorization rules. What powers are you delegating? Common patterns include: - Spending up to a specific amount of a certain ERC-20 token. - Interacting only with a whitelisted set of target smart contract addresses. - Setting a validUntil timestamp for the delegation's expiration. - Limiting the number of times (nonce) the delegation can be used. These rules are encoded into a signed authorization message from the primary account, which the delegation contract will later verify. Using EIP-712 for signing is critical, as it provides human-readable structuring, preventing phishing and replay attacks across different chains.

The smart contract is the source of truth. It must implement a function, often called execute or forward, that: 1. Recovers the signer from the provided EIP-712 signature and authorization parameters. 2. Validates that the recovered signer is the authorized primary account. 3. Checks the authorization rules (amount, target, expiry) against the current transaction details. 4. Executes the requested call if all checks pass. A minimal contract skeleton might inherit from OpenZeppelin's EIP712 and SignatureChecker libraries. The contract must not hold funds directly; it should only be granted allowances via the ERC-20 approve function for the specific tokens and amounts it is authorized to move.

The off-chain agent, which could be a backend service or a meta-transaction relayer, is responsible for operational security. It holds the private key for the delegated signer account, which should be a dedicated, low-value account. Its job is to monitor for conditions requiring action, construct the EIP-712 Authorization message with the current parameters, have the primary account sign it (via a secure method), and then submit the transaction with the delegated signer's key. This agent must implement robust nonce management to prevent replay and gas estimation to ensure transactions succeed. Consider using a service like Gelato Network or OpenZeppelin Defender to automate and secure this relay layer.

Thorough testing is non-negotiable. Write comprehensive unit tests for the delegation contract covering: valid executions, signature forgery attempts, expired authorizations, rule violations (e.g., exceeding spend limit), and replay attacks. Use a development framework like Foundry or Hardhat with a mainnet fork to simulate real interactions. For the off-chain component, implement integration tests that run the full flow from signature generation to on-chain execution. Finally, a security audit by a reputable firm is strongly recommended before deploying any system that will control significant value, as the interaction between signature schemes, gas economics, and authorization logic is complex and error-prone.

A delegated signing authority model allows a user's smart account to grant limited permissions to another key, known as a session key, for a specific period or set of actions. This is critical for improving user experience in applications like gaming or social dApps, where signing every single transaction is impractical. The core security principle is least privilege: the session key should only be authorized for the minimum actions necessary, such as approving specific tokens on a single DEX for a 24-hour period. This model moves beyond the all-or-nothing control of a single Externally Owned Account (EOA) private key.

Implementation begins with defining the validation logic in your smart account. For an ERC-4337-compatible smart account, you modify the validateUserOp function to check for session key signatures. A common pattern is to store a mapping of authorized session keys to a permissions struct. This struct defines the constraints, such as: allowedContracts (e.g., a specific Uniswap router), allowedFunctions (e.g., swapExactTokensForTokens), valueLimit (max ETH value per transaction), and expiryTimestamp. The validation logic must revert if the UserOp is signed by a session key but targets an unauthorized contract or exceeds its limits.

Here is a simplified Solidity example of a session key validation snippet within a smart account:

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function _validateSessionKey(
    UserOperation calldata userOp,
    SessionKey memory session
) internal view returns (bool) {
    if (block.timestamp > session.expiry) revert SessionExpired();
    if (userOp.callData.length < 4) revert InvalidCall();
    bytes4 funcSelector = bytes4(userOp.callData[:4]);
    
    bool isAllowedContract = session.allowedContracts[userOp.target];
    bool isAllowedFunction = session.allowedFunctions[funcSelector];
    bool isUnderValueLimit = userOp.value <= session.maxValue;
    
    return isAllowedContract && isAllowedFunction && isUnderValueLimit;
}

The UserOp signature is then validated against the session key's public address, not the main account's signer.

To create a session, the primary signer of the smart account must sign a message granting these permissions, which is then relayed to the dApp's backend. The dApp can then use this signed message to generate a valid ERC-4337 UserOperation with the session key's signature. It is crucial that the session key's private key is managed securely by the dApp's backend and never exposed to the client-side environment. Best practices include using hardware security modules (HSMs) or dedicated key management services for generation and storage, and rotating keys frequently.

Security audits must focus on the permission validation logic to prevent escalation attacks. Common vulnerabilities include: insufficient validation of callData allowing malicious payloads, incorrectly set expiry times, and failure to enforce per-transaction value limits. Furthermore, the system must include a straightforward mechanism for the primary owner to revoke sessions at any time, typically by clearing the session key from the on-chain mapping. This implementation pattern, when done correctly, provides a robust foundation for seamless yet secure user interactions in wallet-native applications.

A delegated signing authority model allows a primary account (the delegator) to grant specific transaction permissions to secondary accounts (delegates) without transferring asset ownership. This pattern is essential for secure multi-signature wallets, DAO treasuries, and automated trading systems. The core security principle is least privilege: delegates should only have the authority to execute pre-defined actions for a limited time or amount. We'll implement this using Solidity, focusing on a contract that manages allowances for token transfers as a concrete example.

First, we define the core data structures and state variables. The contract needs to track delegations, including the delegate's address, the token contract, a spending limit, and an expiration timestamp. Using a nested mapping is efficient for lookup. We also implement a nonce mechanism to prevent replay attacks on signed messages.

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mapping(address => mapping(bytes32 => Delegation)) public delegations;
mapping(address => uint256) public nonces;

struct Delegation {
    address delegate;
    address token;
    uint256 allowance;
    uint256 expiry;
}

The delegation is created by the owner signing a message (an EIP-712 typed structured data signature) containing the delegation parameters. This signed payload is submitted by anyone to the createDelegation function, which uses ecrecover to verify the signature belongs to the owner. Upon successful verification, the delegation is stored in the mapping. This off-chain signing pattern is gas-efficient and allows for meta-transactions.

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function createDelegation(
    address owner,
    address delegate,
    address token,
    uint256 allowance,
    uint256 expiry,
    uint8 v,
    bytes32 r,
    bytes32 s
) external {
    bytes32 structHash = keccak256(abi.encode(
        DELEGATION_TYPEHASH,
        owner,
        delegate,
        token,
        allowance,
        expiry,
        nonces[owner]++
    ));
    address signer = ecrecover(structHash, v, r, s);
    require(signer == owner, "Invalid signature");
    require(expiry > block.timestamp, "Delegation expired");

    bytes32 delegationId = keccak256(abi.encode(owner, delegate, token));
    delegations[owner][delegationId] = Delegation(delegate, token, allowance, expiry);
}

To execute a transaction, the delegate calls an executeTransfer function. The contract first fetches the active delegation, checks the expiry and remaining allowance, and then performs a safe transferFrom call to the specified ERC20 token contract. Crucially, the contract must reduce the delegation's allowance after a successful transfer and emit an event for off-chain tracking. This ensures the delegated power cannot be exceeded.

solidityCopy
function executeTransfer(
    address owner,
    address token,
    address to,
    uint256 amount
) external returns (bool) {
    bytes32 delegationId = keccak256(abi.encode(owner, msg.sender, token));
    Delegation storage d = delegations[owner][delegationId];

    require(d.delegate == msg.sender, "Not authorized delegate");
    require(d.expiry >= block.timestamp, "Delegation expired");
    require(d.allowance >= amount, "Allowance exceeded");

    d.allowance -= amount;
    bool success = IERC20(token).transferFrom(owner, to, amount);
    require(success, "Token transfer failed");

    emit TransferExecuted(owner, msg.sender, token, to, amount);
    return true;
}

For production use, several critical security enhancements are required. Implement a revocation function that allows the owner to immediately invalidate a delegation. Use OpenZeppelin's SignatureChecker library for more robust signature verification that supports smart contract wallets (ERC-1271). Add rate limiting or timelocks for large transfers. Always conduct thorough audits, as signature replay across chains or contract upgrades is a common vulnerability. The full example code is available in the Chainscore Labs GitHub repository.

Implementing a delegated signing model requires a layered security approach. The foundation is a robust multi-signature wallet like Safe (formerly Gnosis Safe) or a custom smart account using ERC-4337. This acts as the secure vault holding assets and executing transactions. The delegation mechanism itself should be implemented via a purpose-built smart contract that enforces permissions, spending limits, and time-locks. For off-chain signing, integrate a signing service that uses secure, air-gapped hardware or a Threshold Signature Scheme (TSS) to manage private keys without a single point of failure. Always use established libraries like OpenZeppelin for contract security.

Before deploying to mainnet, rigorous testing is non-negotiable. Start with comprehensive unit and integration tests for your delegation contracts. Use tools like Foundry or Hardhat to simulate complex attack vectors, including reentrancy, front-running, and permission bypasses. Conduct audits on a testnet with real transaction flows, involving both automated tools like Slither and manual review by experienced developers. For critical systems, consider engaging a professional audit firm. Document all roles, recovery procedures, and key rotation policies clearly for your team.

To move beyond basic implementations, explore integrating with account abstraction standards. ERC-4337 enables advanced features like session keys for temporary permissions, gas sponsorship, and batched transactions. You can also implement conditional logic in your delegation contracts, such as allowing transfers only after on-chain oracle price feeds meet certain criteria. For DAOs or corporate treasuries, combine this model with governance frameworks like OpenZeppelin Governor to make delegation a part of proposal execution.

The security landscape evolves constantly. Subscribe to security bulletins from the Ethereum Foundation and OpenZeppelin. Monitor your contracts with real-time alerting services like Forta Network or Tenderly. Establish a clear incident response plan. The final step is to contribute back to the community by open-sourcing non-critical components of your implementation, sharing audit reports, and participating in forums to advance the collective security of delegated signing models.