+pub(super) fn derive_keys(nonce: Nonce, expanded_key: &ExpandedKey) -> KeyPair {
+ const IV_BYTES: &[u8; IV_LEN] = b"LDK Invoice ~~~~";
+ let secp_ctx = Secp256k1::new();
+ let hmac = Hmac::from_engine(expanded_key.hmac_for_offer(nonce, IV_BYTES));
+ let privkey = SecretKey::from_slice(hmac.as_inner()).unwrap();
+ KeyPair::from_secret_key(&secp_ctx, &privkey)
+}
+