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Bitcoin–Monero Cross-chain Atomic Swap
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The only reason we need this argument is because we need to access the output descriptor. We can save that one ahead of time at when we construct the type. |
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.github | ||
docs | ||
monero-harness | ||
monero-rpc | ||
swap | ||
tokio-tar | ||
.gitignore | ||
.mergify.yml | ||
bors.toml | ||
BTC_XMR_atomic_swap_protocol.svg | ||
Cargo.lock | ||
Cargo.toml | ||
LICENSE | ||
README.md | ||
rust-toolchain | ||
rustfmt.toml |
XMR to BTC Atomic Swap
This repository is a proof of concept for atomically swapping XMR for BTC.
We define:
- Alice to be the actor that initially holds XMR.
- Bob to be the actor that initially holds BTC.
In the best-case scenario the protocol looks like this:
- Alice and Bob exchange a set of addresses, keys, zero-knowledge proofs and signatures.
- Bob publishes
Tx_lock
, locking up his bitcoin in a 2-of-2 multisig output owned by Alice and Bob. Given the information exchanged in step 1, Bob can refund his bitcoin if he waits until timet_1
by usingTx_cancel
andTx_refund
. If Bob doesn't refund after timet_1
, Alice can punish Bob for being inactive by first publishingTx_cancel
and, aftert_2
, spending the output usingTx_punish
. - Alice sees that Bob has locked up the bitcoin, so she publishes
Tx_lock
on the Monero blockchain, locking up her monero in an output which can only be spent with a secret key owned by Alice (s_a
) and a secret key owned by Bob (s_b
). This means that neither of them can actually spend this output unless they learn the secret key of the other party. - Bob sees that Alice has locked up the monero, so he now sends Alice a missing key bit of information which will allow Alice to redeem the bitcoin using
Tx_redeem
. - Alice uses this information to spend the bitcoin to an address owned by her.
When doing so she leaks her Monero secret key
s_a
to Bob through the magic of adaptor signatures. - Bob sees Alice's
Tx_redeem
on Bitcoin, extracts Alice's secret key from it and combines it with his own to spend the monero to an address of his own.
The repository is structured as a library and a single test function that executes the swap. The library has the following modules:
alice
: Defines the state machine that describes the swap for Alice. This includes the messages sent to/from Alice.bob
: Defines the state machine that describes the swap for Bob. This includes the messages sent to/from Bob.bitcoin
: Keys, signing functions, transactions etc. for Bitcoin. Also includes a test wallet (see below).monero
: Keys, signing functions, transactions etc. for Monero. Also includes a test wallet (see below).
Currently we have a single test function that proves the following:
- Interaction with both block chains and their respective wallets works.
- The messages required are correct and can manually drive the state transitions to execute a swap.
- It is possible to interact with, and watch, the monero blockchain using
monero-wallet-rpc
. - It is possible to watch a bitcoind instance using
bitcoin-harness
(we already knew this :)
Currently we do not do:
- Actual network communication.
- Verification that the UI is acceptable. Since we do everything in a single test function there is no user interaction, this is unrealistic for a real product.
Testing
We wrote a few additional libraries to facilitate testing:
Wallets
bitcoin
module contains a test wallet by way ofbitcoind
.monero
: module contains a test wallet by way ofmonero-wallet-rpc
.
Blockchain harnesses
We have written two harnesses for interacting with bitcoin and monero.
These harnesses wrap interaction with bitcoind
and monerod
/monero-wallet-rpc
.
We use testcontainers-rs to spin up bitcoind
, monerod
, and monero-wallet-rpc
in docker containers during unit/integration testing.