Lightning Integration

Trustless atomic swaps between Citrea and Lightning Network are being actively implemented at the moment through third-party applications, such as Atomiq. This will allow users of Citrea to pay Lightning invoices directly from the Citrea network or on- and off-ramp from Citrea without needing to leverage the Bitcoin base layer.

For both swap directions, the smart contract on Citrea simply emulates Lightning's HTLC. An LP (Liquidity Provider) behaves as a proxy on Lightning and it is responsible for all cross-network interactions - with liquidity maintained on both sides.

Lightning Atomic Swap Diagram

For the path from Lightning to Citrea, here's a basic explanation:

• The receiver on the LN side creates an invoice and sends it to the sender on Citrea side.

• Sender locks cBTC on the HTLC contract with the invoice.

• LP makes the payment on LN on behalf of the sender.

• The preimage of the invoice gets revealed to the LP upon payment.

• LP uses the preimage to claim the cBTC from the HTLC contract.