From 665d95554dbc0cb4788d951602ad3d84f9546c0b Mon Sep 17 00:00:00 2001
From: Sosthene <contact@sosthene.net>
Date: Wed, 21 Aug 2024 13:17:34 +0200
Subject: [PATCH] Add basic signature

---
 src/lib.rs       |  1 +
 src/signature.rs | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 src/signature.rs

diff --git a/src/lib.rs b/src/lib.rs
index e4247f8..12aa3a0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,3 +6,4 @@ pub mod error;
 pub mod network;
 pub mod process;
 pub mod silentpayments;
+pub mod signature;
diff --git a/src/signature.rs b/src/signature.rs
new file mode 100644
index 0000000..b965962
--- /dev/null
+++ b/src/signature.rs
@@ -0,0 +1,45 @@
+use anyhow::Result;
+use rand::{thread_rng, RngCore};
+use sp_client::bitcoin::key::Secp256k1;
+use sp_client::bitcoin::secp256k1::schnorr::Signature;
+use sp_client::bitcoin::secp256k1::{Keypair, Message, SecretKey, XOnlyPublicKey};
+use sp_client::bitcoin::hashes::{sha256t_hash_newtype, Hash, HashEngine};
+
+sha256t_hash_newtype! {
+    pub struct AnkMessageTag = hash_str("4nk/Message");
+
+    #[hash_newtype(forward)]
+    pub struct AnkMessageHash(_);
+}
+
+impl AnkMessageHash {
+    pub fn from_message(message: &[u8]) -> Self {
+        let mut eng = AnkMessageHash::engine();
+        eng.input(&message);
+        AnkMessageHash::from_engine(eng)
+    }
+}
+
+pub fn sign_message(message: &[u8], signing_key: SecretKey) -> Result<Signature> {
+    let message_hash = AnkMessageHash::from_message(message);
+
+    let secp = Secp256k1::signing_only();
+
+    let keypair = Keypair::from_secret_key(&secp, &signing_key);
+
+    let mut aux_rand = [0u8; 32];
+
+    thread_rng().fill_bytes(&mut aux_rand);
+
+    let sig = secp.sign_schnorr_with_aux_rand(&Message::from_digest(message_hash.to_byte_array()), &keypair, &aux_rand);
+
+    Ok(sig)
+}
+
+pub fn verify(sig: Signature, message: &[u8], x_only_key: XOnlyPublicKey) -> Result<()> {
+    let secp = Secp256k1::verification_only();
+    let message_hash = AnkMessageHash::from_message(message);
+    secp.verify_schnorr(&sig, &Message::from_digest(message_hash.to_byte_array()), &x_only_key)?;
+
+    Ok(())
+}
\ No newline at end of file