Generate Events from ChannelMonitor to indicate spendable ouputs

Extend KeyStorage with delayed_payment_base_key and per_commitment_point
to derive local_delayed private key

Author: Antoine Riard

src/chain/keysinterface.rs

@@ -0,0 +1,34 @@
+//! keysinterface provides keys into rust-lightning and defines some useful enums which describe
+//! spendable on-chain outputs which the user owns and is responsible for using just as any other
+//! on-chain output which is theirs.
+
+use bitcoin::blockdata::transaction::{OutPoint, TxOut};
+use bitcoin::blockdata::script::Script;
+
+use secp256k1::key::SecretKey;
+
+/// When on-chain outputs are created by rust-lightning an event is generated which informs the
+/// user thereof. This enum descibes the format of the output and provides the OutPoint.
+pub enum SpendableOutputDescriptor {
+	/// Outpoint with an output to a script which was provided via KeysInterface, thus you should
+	/// have stored somewhere how to spend script_pubkey!
+	StaticOutput {
+		/// The outpoint spendable by user wallet
+		outpoint: OutPoint,
+		/// The output which is referenced by the given outpoint
+		output: TxOut,
+	},
+	/// Outpoint commits to a P2WSH, should be spend by the following witness :
+	/// <local_delayedsig> 0 <witnessScript>
+	/// With input nSequence set to_self_delay.
+	DynamicOutput {
+		/// Outpoint spendable by user wallet
+		outpoint: OutPoint,
+		/// local_delayedkey = delayed_payment_basepoint_secret + SHA256(per_commitment_point || delayed_payment_basepoint
+		local_delayedkey: SecretKey,
+		/// witness redeemScript encumbering output
+		witness_script: Script,
+		/// nSequence input must commit to self_delay to satisfy script's OP_CSV
+		to_self_delay: u16,
+	}
+}

src/chain/mod.rs

@@ -2,3 +2,4 @@
 
 pub mod chaininterface;
 pub mod transaction;
+pub mod keysinterface;

src/ln/channel.rs

@@ -489,8 +489,7 @@ impl Channel {
 		let secp_ctx = Secp256k1::new();
 		let our_channel_monitor_claim_key_hash = Hash160::from_data(&PublicKey::from_secret_key(&secp_ctx, &chan_keys.channel_monitor_claim_key).serialize());
 		let our_channel_monitor_claim_script = Builder::new().push_opcode(opcodes::All::OP_PUSHBYTES_0).push_slice(&our_channel_monitor_claim_key_hash[..]).into_script();
-		let channel_monitor = ChannelMonitor::new(&chan_keys.revocation_base_key,
-		                                          &PublicKey::from_secret_key(&secp_ctx, &chan_keys.delayed_payment_base_key),
+		let channel_monitor = ChannelMonitor::new(&chan_keys.revocation_base_key, &chan_keys.delayed_payment_base_key,
 		                                          &chan_keys.htlc_base_key,
 		                                          BREAKDOWN_TIMEOUT, our_channel_monitor_claim_script);
 
@@ -651,8 +650,7 @@ impl Channel {
 		let secp_ctx = Secp256k1::new();
 		let our_channel_monitor_claim_key_hash = Hash160::from_data(&PublicKey::from_secret_key(&secp_ctx, &chan_keys.channel_monitor_claim_key).serialize());
 		let our_channel_monitor_claim_script = Builder::new().push_opcode(opcodes::All::OP_PUSHBYTES_0).push_slice(&our_channel_monitor_claim_key_hash[..]).into_script();
-		let mut channel_monitor = ChannelMonitor::new(&chan_keys.revocation_base_key,
-		                                              &PublicKey::from_secret_key(&secp_ctx, &chan_keys.delayed_payment_base_key),
+		let mut channel_monitor = ChannelMonitor::new(&chan_keys.revocation_base_key, &chan_keys.delayed_payment_base_key,
 		                                              &chan_keys.htlc_base_key,
 		                                              BREAKDOWN_TIMEOUT, our_channel_monitor_claim_script);
 		channel_monitor.set_their_base_keys(&msg.htlc_basepoint, &msg.delayed_payment_basepoint);