KeysInterface: add new ecdh method

[rust-lightning] / lightning / src / chain / keysinterface.rs

diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs
index 4231d08259abcbe1e4c50550f4b40aa7d7064faa..9a3baea8bb442a3c6928cca83559606a66de95ff 100644 (file)
--- a/lightning/src/chain/keysinterface.rs
+++ b/lightning/src/chain/keysinterface.rs
@@ -27,6 +27,7 @@ use bitcoin::hash_types::WPubkeyHash;
 
 use bitcoin::secp256k1::{SecretKey, PublicKey};
 use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature, Signing};
+use bitcoin::secp256k1::ecdh::SharedSecret;
 use bitcoin::secp256k1::ecdsa::RecoverableSignature;
 use bitcoin::{secp256k1, Witness};
 
@@ -404,6 +405,12 @@ pub trait KeysInterface {
        /// This method must return the same value each time it is called with a given `Recipient`
        /// parameter.
        fn get_node_secret(&self, recipient: Recipient) -> Result<SecretKey, ()>;
+       /// Gets the ECDH shared secret of our [`node secret`] and `other_key`, multiplying by `tweak` if
+       /// one is provided. Note that this tweak can be applied to `other_key` instead of our node
+       /// secret, though this is less efficient.
+       ///
+       /// [`node secret`]: Self::get_node_secret
+       fn ecdh(&self, recipient: Recipient, other_key: &PublicKey, tweak: Option<&[u8; 32]>) -> Result<SharedSecret, ()>;
        /// Get a script pubkey which we send funds to when claiming on-chain contestable outputs.
        ///
        /// This method should return a different value each time it is called, to avoid linking
@@ -1133,6 +1140,14 @@ impl KeysInterface for KeysManager {
                }
        }
 
+       fn ecdh(&self, recipient: Recipient, other_key: &PublicKey, tweak: Option<&[u8; 32]>) -> Result<SharedSecret, ()> {
+               let mut node_secret = self.get_node_secret(recipient)?;
+               if let Some(tweak) = tweak {
+                       node_secret.mul_assign(tweak).map_err(|_| ())?;
+               }
+               Ok(SharedSecret::new(other_key, &node_secret))
+       }
+
        fn get_inbound_payment_key_material(&self) -> KeyMaterial {
                self.inbound_payment_key.clone()
        }
@@ -1217,6 +1232,14 @@ impl KeysInterface for PhantomKeysManager {
                }
        }
 
+       fn ecdh(&self, recipient: Recipient, other_key: &PublicKey, tweak: Option<&[u8; 32]>) -> Result<SharedSecret, ()> {
+               let mut node_secret = self.get_node_secret(recipient)?;
+               if let Some(tweak) = tweak {
+                       node_secret.mul_assign(tweak).map_err(|_| ())?;
+               }
+               Ok(SharedSecret::new(other_key, &node_secret))
+       }
+
        fn get_inbound_payment_key_material(&self) -> KeyMaterial {
                self.inbound_payment_key.clone()
        }