Merge network::Seed into crate::Seed

This allows us to unify the way we derive new secret key material
and simplify the usage of seed by only having a single one.

swap/src/bin/asb.rs

@@ -89,7 +89,7 @@ async fn main() -> Result<()> {
             let (bitcoin_wallet, monero_wallet) = init_wallets(
                 config.clone(),
                 &wallet_data_dir,
-                seed.extended_private_key(BITCOIN_NETWORK)?,
+                seed.derive_extended_private_key(BITCOIN_NETWORK)?,
             )
             .await?;
 

swap/src/bin/swap_cli.rs

@@ -256,7 +256,7 @@ async fn init_bitcoin_wallet(
         config.bitcoin.electrum_http_url,
         bitcoin_network,
         bitcoin_wallet_data_dir,
-        seed.extended_private_key(bitcoin_network)?,
+        seed.derive_extended_private_key(bitcoin_network)?,
     )
     .await?;
 

swap/src/network.rs

@@ -2,10 +2,8 @@ pub mod peer_tracker;
 pub mod request_response;
 pub mod transport;
 
-use crate::seed::SEED_LENGTH;
-use bitcoin::hashes::{sha256, Hash, HashEngine};
 use futures::prelude::*;
-use libp2p::{core::Executor, identity::ed25519};
+use libp2p::core::Executor;
 use std::pin::Pin;
 use tokio::runtime::Handle;
 
@@ -19,35 +17,3 @@ impl Executor for TokioExecutor {
         let _ = self.handle.spawn(future);
     }
 }
-
-#[derive(Debug, Clone, Copy, Eq, PartialEq)]
-pub struct Seed([u8; SEED_LENGTH]);
-
-impl Seed {
-    /// prefix "NETWORK" to the provided seed and apply sha256
-    pub fn new(seed: crate::seed::Seed) -> Self {
-        let mut engine = sha256::HashEngine::default();
-
-        engine.input(&seed.bytes());
-        engine.input(b"NETWORK");
-
-        let hash = sha256::Hash::from_engine(engine);
-        Self(hash.into_inner())
-    }
-
-    fn bytes(&self) -> [u8; SEED_LENGTH] {
-        self.0
-    }
-
-    pub fn derive_libp2p_identity(&self) -> libp2p::identity::Keypair {
-        let mut engine = sha256::HashEngine::default();
-
-        engine.input(&self.bytes());
-        engine.input(b"LIBP2P_IDENTITY");
-
-        let hash = sha256::Hash::from_engine(engine);
-        let key =
-            ed25519::SecretKey::from_bytes(hash.into_inner()).expect("we always pass 32 bytes");
-        libp2p::identity::Keypair::Ed25519(key.into())
-    }
-}

swap/src/protocol/alice/event_loop.rs

@@ -5,7 +5,6 @@ use crate::{
     execution_params::ExecutionParams,
     monero,
     monero::{Amount, BalanceTooLow},
-    network,
     network::{transport, TokioExecutor},
     protocol::{
         alice,
@@ -113,7 +112,7 @@ where
         rate_service: RS,
         max_sell: Amount,
     ) -> Result<(Self, mpsc::Receiver<RemoteHandle<Result<AliceState>>>)> {
-        let identity = network::Seed::new(seed).derive_libp2p_identity();
+        let identity = seed.derive_libp2p_identity();
         let behaviour = Behaviour::default();
         let transport = transport::build(&identity)?;
         let peer_id = PeerId::from(identity.public());

swap/src/protocol/bob.rs

@@ -4,7 +4,7 @@ use crate::{
     bitcoin,
     database::Database,
     execution_params::ExecutionParams,
-    monero, network,
+    monero,
     network::peer_tracker::{self, PeerTracker},
     protocol::{alice, alice::TransferProof, bob},
     seed::Seed,
@@ -79,7 +79,7 @@ impl Builder {
         alice_peer_id: PeerId,
         execution_params: ExecutionParams,
     ) -> Self {
-        let identity = network::Seed::new(seed).derive_libp2p_identity();
+        let identity = seed.derive_libp2p_identity();
 
         Self {
             swap_id,

swap/src/seed.rs

@@ -2,6 +2,8 @@ use crate::fs::ensure_directory_exists;
 use ::bitcoin::secp256k1::{self, constants::SECRET_KEY_SIZE, SecretKey};
 use anyhow::Result;
 use bdk::bitcoin::util::bip32::ExtendedPrivKey;
+use bitcoin::hashes::{sha256, Hash, HashEngine};
+use libp2p::identity;
 use pem::{encode, Pem};
 use rand::prelude::*;
 use std::{
@@ -28,13 +30,21 @@ impl Seed {
         Ok(Seed(bytes))
     }
 
-    pub fn extended_private_key(&self, network: bitcoin::Network) -> Result<ExtendedPrivKey> {
-        let private_key = ExtendedPrivKey::new_master(network, &self.bytes())?;
+    pub fn derive_extended_private_key(
+        &self,
+        network: bitcoin::Network,
+    ) -> Result<ExtendedPrivKey> {
+        let seed = self.derive(b"BITCOIN_EXTENDED_PRIVATE_KEY").bytes();
+        let private_key = ExtendedPrivKey::new_master(network, &seed)?;
+
         Ok(private_key)
     }
 
-    pub fn bytes(&self) -> [u8; SEED_LENGTH] {
-        self.0
+    pub fn derive_libp2p_identity(&self) -> identity::Keypair {
+        let bytes = self.derive(b"NETWORK").derive(b"LIBP2P_IDENTITY").bytes();
+        let key = identity::ed25519::SecretKey::from_bytes(bytes).expect("we always pass 32 bytes");
+
+        identity::Keypair::Ed25519(key.into())
     }
 
     pub fn from_file_or_generate(data_dir: &Path) -> Result<Self, Error> {
@@ -53,6 +63,26 @@ impl Seed {
         Ok(random_seed)
     }
 
+    /// Derive a new seed using the given scope.
+    ///
+    /// This function is purposely kept private because it is only a helper
+    /// function for deriving specific secret material from the root seed
+    /// like the libp2p identity or the seed for the Bitcoin wallet.
+    fn derive(&self, scope: &[u8]) -> Self {
+        let mut engine = sha256::HashEngine::default();
+
+        engine.input(&self.bytes());
+        engine.input(scope);
+
+        let hash = sha256::Hash::from_engine(engine);
+
+        Self(hash.into_inner())
+    }
+
+    fn bytes(&self) -> [u8; SEED_LENGTH] {
+        self.0
+    }
+
     fn from_file<D>(seed_file: D) -> Result<Self, Error>
     where
         D: AsRef<OsStr>,

swap/tests/testutils/mod.rs

@@ -606,7 +606,7 @@ async fn init_test_wallets(
         electrum_http_url,
         bitcoin::Network::Regtest,
         datadir,
-        seed.extended_private_key(bitcoin::Network::Regtest)
+        seed.derive_extended_private_key(bitcoin::Network::Regtest)
             .expect("Could not create extended private key from seed"),
     )
     .await