mirror of
https://github.com/lightninglabs/loop
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68 lines
4.3 KiB
Markdown
68 lines
4.3 KiB
Markdown
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# Loop Architecture
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Lightning Loop's architecture for orchestrating submarine swaps is based on a
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client/server concept.
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The client has a swap execution daemon `loopd` controlled by a CLI application
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`loop` which uses a gRPC API. The client daemon initiates swaps and handles
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their progress through swap phases. To manage keys and the connection to the
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LN/BTC network layers the client daemon connects to a local lnd wallet.
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Client daemons communicate with the Loop server daemon, which is opaque but
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operates in a similar way. The server is not a trusted component in this
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architecture; the client daemon validates that the terms of the swap are
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acceptable and the server cannot access the swap funds unless the swap enters
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the "complete" phase.
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## Loop Out Swap (off -> on-chain)
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Phases:
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1. Initiation: Client queries for terms of a swap
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2. Fee: Client sends a small fee HTLC that is unrestricted
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3. Funding: Client sends a funding HTLC locked to a preimage they generate
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4. Payment: Server sends the funds on-chain locked to the funding preimage hash
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5. Complete: Client uses the preimage to take the on-chain funds.
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6. Final: The server uses the on-chain-revealed preimage to claim funding HTLC
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```
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loop out 500
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v
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.-----------------------------.
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| Loop CLI |
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| ./cmd/loop |
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| .-------------------. | .--------------. .---------------.
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| | Loop Client (lib) | | | LND node | | Bitcoin node |
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| | ./ |<-------------| |-------------------| |
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| | | | | | on-chain | |
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| | |------------->| | htlc | |
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| | | | off-chain | | | |
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| '-------------------' | htlc '--------------' '---------------'
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'-----------------|-----------' | ^
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| v |
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| .--. .--.
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| _ -( )- _ _ -( )- _
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| .--,( ),--. .--,( ),--.
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initiate| _.-( )-._ _.-( )-._
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swap | ( LIGHTNING NETWORK ) ( BITCOIN NETWORK )
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| '-._( )_.-' '-._( )_.-'
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| '__,( ),__' '__,( ),__'
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| - ._(__)_. - - ._(__)_. -
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v v |
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.--------------------. off-chain .--------------. .---------------.
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| Loop Server | htlc | LND node | | Bitcoin node |
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| |<-------------| | | |
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| | | | on-chain | |
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| | | | htlc | |
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| |--------------| |----------------->| |
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'--------------------' '--------------' '---------------'
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```
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