SignatureQueue

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Purpose

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Key Features

• Instant execution without waiting for oracle price reports
• Nonce-based signature protection to prevent replay attacks
• EIP-712/EIP-1271 compatible signed orders
• Oracle price validation enforced on-chain
• Stateless and removable (i.e., does not accumulate shares or process claims)
• Fee-bypassed: No depositFee or redeemFee is charged for actions via this queue

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High-Level Workflow

1. Off-chain consensus actors (e.g., operators, curators, admins) generate signed Order messages.
2. A user submits this order to the SignatureQueue contract for execution.
3. The queue:
   • Verifies the order signature
   • Validates nonce, queue address, asset match, deadline, and caller
   • Computes the implied asset/share price and checks it against the vault’s oracle
4. If all checks pass, the order is executed atomically.

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Order Structure

struct Order {
    uint256 orderId;       // Off-chain tracking ID
    address queue;         // Must match queue address
    address asset;         // Token involved in deposit/redeem
    address caller;        // Must match msg.sender
    address recipient;     // Recipient of assets or shares
    uint256 ordered;       // Assets in (deposit) or shares out (redeem)
    uint256 requested;     // Shares out (deposit) or assets in (redeem)
    uint256 deadline;      // Expiration timestamp
    uint256 nonce;         // Unique per caller
}

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Signature Validation

• Orders are signed by a quorum of validators registered in the Consensus contract.
• Signatures can conform to:
  • EIP-712 (structured message hashing)
  • EIP-1271 (smart contract-based signature schemes)

keccak256(
    abi.encode(
        ORDER_TYPEHASH,
        order.orderId,
        order.queue,
        order.asset,
        order.caller,
        order.recipient,
        order.ordered,
        order.requested,
        order.deadline,
        order.nonce
    )
);

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Price Safety Check

• Deposits: price = requestedShares / depositedAssets
• Redemptions: price = burnedShares / redeemedAssets
• Oracle must confirm:
  • Price is within allowed bounds
  • Price is not marked as suspicious

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Storage Layout

struct SignatureQueueStorage {
    address consensus;                        // Signature validator contract
    address vault;                            // Parent vault (Vault.sol)
    address asset;                            // Supported ERC20 token or native ETH
    mapping(address => uint256) nonces;       // Per-user nonces
}

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Interface Compatibility

• claimableOf(...) → 0
• claim(...) → false
• handleReport(...): no-op
• canBeRemoved() → true: confirms it has no persistent state

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Events

event OrderExecuted(Order order, IConsensus.Signature[] signatures);

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Security Assumptions

• Only trusted off-chain actors (consensus group) are authorized to sign orders.
• Price quotes must match oracle-defined asset/share rates.
• Users cannot reuse old signatures due to nonce tracking.
• Orders must be executed before deadline.

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Use Cases

• Instant UX: bypassing delays in DepositQueue or RedeemQueue
• Institutional integrations: where trusted relayers or coordinators pre-sign valid actions
• Fallback mechanism: during oracle lags or downtime

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Limitations

• Does not charge fees (unlike time-delayed queues)
• Requires trusted off-chain actors
• Less decentralized if consensus actors are not well-audited or rotated