System transactions

Transactions on Signet can originate from Ethereum. Signet’s consensus rules specify that certain events emitted by the Passage and Transactor contracts on the host chain produce corresponding transactions on the rollup.

Three host-chain event types produce system transactions:

System transactions execute last in the block, after all user-submitted transactions. Host events are processed in the following order:

1. Enter — all ETH deposit mints
2. EnterToken — all token deposit mints, in host event order
3. Transact — all host-originated execution

Because EnterToken events are processed in host event order, native asset mints (USD) and non-native token mints (e.g. WBTC) are interleaved rather than grouped by type.

A single host transaction can produce multiple system transactions. For example, the Transactor’s enterTransact function emits both an Enter event and a Transact event, producing two system transactions in the same block.

Magic signature

System transactions are not signed by a private key. The signature field carries a magic signature — a value with the same RLP structure as a standard Ethereum signature (r, s, y_parity) but which is not a valid ECDSA signature. It encodes three fields:

• Event type: Enter, EnterToken, or Transact
• Transaction hash: the host-chain transaction that emitted the event
• Event index: position of the event within the transaction’s logs

The s value of the signature begins with the sentinel 0xffeeddcc, which exceeds the secp256k1 curve order. This makes it impossible to confuse a magic signature with a real ECDSA signature on any EIP-2 chain.

For Transact events, the magic signature also encodes the sender address and whether address aliasing was applied.

See the MagicSig documentation for the full wire format specification.

Native asset mints

When USDC or USDT is deposited through Passage (EnterToken event), the recipient’s native USD balance is increased directly. This is not an EVM transaction — no contract code is executed.

Amounts are normalized from the host token’s decimals to 18. For example, 1 USDC (10**6 on Ethereum) becomes 10**18 wei of native USD on Signet.

The transaction emits a MintNative log from MINTER_ADDRESS (0x00000000000000000000746f6b656e61646d696e). The txHash and logIndex fields reference the originating host-chain event, allowing indexers to connect rollup-side mints to their host-chain deposits.

event MintNative(
    bytes32 indexed txHash,
    uint64 indexed logIndex,
    address indexed recipient,
    uint256 amount
);

Token mints

ETH deposits (Enter) and non-USD token deposits (EnterToken) produce a system transaction that calls mint(recipient, amount) on the corresponding rollup-side ERC-20 contract.

These transactions run from MINTER_ADDRESS with zero gas cost.

Transaction properties:

• from: MINTER_ADDRESS
• to: the rollup token contract
• value: 0
• nonce: next nonce for MINTER_ADDRESS
• input: ABI-encoded mint(address recipient, uint256 amount)
• max_fee_per_gas: 0
• max_priority_fee_per_gas: 0

The transaction emits a MintToken log from MINTER_ADDRESS. As with MintNative, the txHash and logIndex fields reference the originating host-chain event for indexer correlation.

event MintToken(
    bytes32 indexed txHash,
    uint64 indexed logIndex,
    address indexed recipient,
    address hostToken,
    uint256 amount
);

Transact

When the host Transactor emits a Transact event, it triggers a system transaction on Signet from the caller’s address. This allows Ethereum contracts to own assets on Signet and trigger execution there, using their Ethereum address as the sender.

Transaction properties:

• from: the host-chain msg.sender, aliased if the sender is a smart contract
• to: as specified in the event
• value: as specified in the event (USD wei)
• input: as specified in the event
• nonce: next nonce for the sender’s Signet account
• gas_limit: as specified in the event
• max_fee_per_gas: as specified in the event
• max_priority_fee_per_gas: 0