Design protocol for integrating LND into cnd

[bonomat]

Problem

Doing an atomic swap with on-chain transactions is constrained by the underlying blockchain. This has several downsides:

• Transactions are bound to the blocktime. This means, an atomic swap between Bitcoin and Ethereum using on-chain transactions would take on average more than 20 minutes provided both parties are fine with 1 confirmation.
• Transactions are expensive and the fee needs to be calculated ad-hoc according to network congestions.
• The atomic swap is traceable as both on-chain transactions include the same hash.

Goal

Come up with a new protocol for adding support for LND in cnd.

[kilrau]

Check https://opendex.network/

[thomaseizinger]

So actually, I kind of scope-creeped https://github.com/comit-network/comit-rs/issues/1838 so the protocol is already part of that.

I am closing this issue in favor of https://github.com/comit-network/comit-rs/issues/1838.