Bitcoin on other networks

Mostro can swap Lightning sats for bitcoin on another network. The asset is the order's currency, in the f tag where a fiat order has its ISO 4217 code, and each asset is pegged 1:1 to bitcoin itself:

Codes are upper-case.

Amounts are in sats

For these codes fa counts sats of the asset, not whole units: fa = 100000 is 0.001 RBTC. A range order's two fa values are sats too.

["k", "sell"],
["f", "RBTC"],
["amt", "0"],
["fa", "100000"],
["pm", "RBTC (Rootstock)"],
["premium", "1"]

• Clients MUST read and write fa in sats for these codes. A client that shows fa with the code as if it were a whole unit would show "100000 RBTC" for 0.001 RBTC.
• Clients SHOULD let users enter and see these amounts in sats, or convert them to the asset with 8 decimals.
• RBTC has 18 decimals on Rootstock. A client rounds an RBTC amount to the sat (10⁻⁸ RBTC) before it builds the order.

Price

A node publishes each of these codes that it quotes at 100000000 in its exchange rates event: 10⁸ units per BTC, a unit being a sat. An operator may quote any subset of the three. A market-priced order (amt = 0) is therefore fa sats, less the premium:

sats = fa × (1 − premium / 100), rounded to the nearest sat

The order above is 99,000 sats: the seller locks 99,000 Lightning sats and receives 100,000 sats of RBTC. The premium is the price of the swap. A fixed-price order (amt > 0) states both amounts, as for fiat.

Pricing these codes is the operator's choice, as for stablecoins:

• A node that quotes a code publishes it in its exchange rates event.
• A node that does not quote it refuses market-priced orders in it. It may still accept fixed-price ones, if fiat_currencies_accepted allows the code.
• A node with MostroP2P/mostro#1095 checks a market order against its sats limits (min_order_amount, max_order_amount) with the premium applied. An earlier node checks them without it, so an order close to a limit can pass creation and be taken outside it.

Clients SHOULD offer market price for these codes only when the node's exchange rates event carries the code.

The exchange rates content keeps its outer "BTC" key, so on-chain bitcoin appears as an inner "BTC" entry. Only 100000000 there means the node quotes it. A value of 1 is a source's bitcoin-to-bitcoin self-rate, not a quote, and clients SHOULD ignore it.

Network

The code names the network, so an order needs no network choice. Clients SHOULD still write the payment method as <CODE> (<Network>), as for stablecoins, so that the order book reads the same way for every pegged code:

The daemon does not check pm; it publishes the methods as written.

Settlement and disputes

The trade runs as with fiat: the buyer sends the asset, then sends fiat-sent, and the seller releases once it has arrived.

• The seller releases only after the transfer confirms, never on zero confirmations.
• The window is the node's escrow deadline, not the hold invoice's full life. Near the hold invoice's expiry the node cancels an active trade, or opens a dispute on a fiat-sent one. With the daemon's default settings that is about 120 blocks after the seller's payment is accepted. Liquid and Rootstock confirm in minutes. On-chain BTC sent with a low fee can stay unconfirmed past the deadline, so the sender SHOULD pay a fee that confirms within a few hours.
• The sender pays the network fee. The receiver must get the full fa sats.
• The buyer SHOULD paste the transaction id in the peer chat.
  • BTC and RBTC transfers are public, so a solver checks them in an explorer.
  • Liquid transactions are confidential, with amounts and assets blinded. The sender SHOULD share the unblinded link, which carries the blinding data, so that a solver can see the amount and the asset.

Compatibility

f is NIP-69's tag, defined there as an ISO 4217 code. A NIP-69 client that checks for one will likely skip these orders.

A client that accepts any code but does not know these would read fa as whole units. Any client can already publish a fixed-price order in these codes, so the sats rule applies whether or not a node quotes them.