WIP: Upgrade to secp256k1 v0.23.2

We recently released a new version of `rust-secp256k1`, upgrade to use
it.

WIP because currently includes an `excect` that needs removing.

Cargo.toml

@@ -36,7 +36,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 [dependencies]
 bech32 = { version = "0.8.1", default-features = false }
 bitcoin_hashes = { version = "0.10.0", default-features = false }
-secp256k1 = { version = "0.22.0", default-features = false }
+secp256k1 = { version = "0.23.2", default-features = false }
 core2 = { version = "0.3.0", optional = true, default-features = false }
 
 base64 = { version = "0.13.0", optional = true }
@@ -48,7 +48,7 @@ hashbrown = { version = "0.8", optional = true }
 [dev-dependencies]
 serde_json = "<1.0.45"
 serde_test = "1"
-secp256k1 = { version = "0.22.0", features = [ "recovery", "rand-std" ] }
+secp256k1 = { version = "0.23.2", features = [ "recovery", "rand-std" ] }
 bincode = "1.3.1"
 
 [[example]]

src/util/bip32.rs

@@ -600,15 +600,15 @@ impl ExtendedPrivKey {
 
         hmac_engine.input(&endian::u32_to_array_be(u32::from(i)));
         let hmac_result: Hmac<sha512::Hash> = Hmac::from_engine(hmac_engine);
-        let mut sk = secp256k1::SecretKey::from_slice(&hmac_result[..32])?;
-        sk.add_assign(&self.private_key[..])?;
+        let sk = secp256k1::SecretKey::from_slice(&hmac_result[..32])?;
+        let tweaked = sk.add_tweak(&self.private_key.into())?;
 
         Ok(ExtendedPrivKey {
             network: self.network,
             depth: self.depth + 1,
             parent_fingerprint: self.fingerprint(secp),
             child_number: i,
-            private_key: sk,
+            private_key: tweaked,
             chain_code: ChainCode::from(&hmac_result[32..])
         })
     }
@@ -741,15 +741,14 @@ impl ExtendedPubKey {
         i: ChildNumber,
     ) -> Result<ExtendedPubKey, Error> {
         let (sk, chain_code) = self.ckd_pub_tweak(i)?;
-        let mut pk = self.public_key;
-        pk.add_exp_assign(secp, &sk[..])?;
+        let tweaked = self.public_key.add_exp_tweak(secp, &sk.into())?;
 
         Ok(ExtendedPubKey {
             network: self.network,
             depth: self.depth + 1,
             parent_fingerprint: self.fingerprint(),
             child_number: i,
-            public_key: pk,
+            public_key: tweaked,
             chain_code,
         })
     }

src/util/schnorr.rs

@@ -21,7 +21,6 @@ use core::fmt;
 use crate::prelude::*;
 
 use secp256k1::{self, Secp256k1, Verification, constants};
-use crate::hashes::Hash;
 use crate::util::taproot::{TapBranchHash, TapTweakHash};
 use crate::SchnorrSighashType;
 
@@ -110,11 +109,10 @@ impl TapTweak for UntweakedPublicKey {
     /// # Returns
     /// The tweaked key and its parity.
     fn tap_tweak<C: Verification>(self, secp: &Secp256k1<C>, merkle_root: Option<TapBranchHash>) -> (TweakedPublicKey, secp256k1::Parity) {
-        let tweak_value = TapTweakHash::from_key_and_tweak(self, merkle_root).into_inner();
-        let mut output_key = self;
-        let parity = output_key.tweak_add_assign(secp, &tweak_value).expect("Tap tweak failed");
+        let tweak = TapTweakHash::from_key_and_tweak(self, merkle_root).to_scalar();
+        let (output_key, parity) = self.add_tweak(secp, &tweak).expect("Tap tweak failed");
 
-        debug_assert!(self.tweak_add_check(secp, &output_key, parity, tweak_value));
+        debug_assert!(self.tweak_add_check(secp, &output_key, parity, tweak));
         (TweakedPublicKey(output_key), parity)
     }
 
@@ -139,11 +137,11 @@ impl TapTweak for UntweakedKeyPair {
     ///
     /// # Returns
     /// The tweaked key and its parity.
-    fn tap_tweak<C: Verification>(mut self, secp: &Secp256k1<C>, merkle_root: Option<TapBranchHash>) -> TweakedKeyPair {
-        let pubkey = crate::XOnlyPublicKey::from_keypair(&self);
-        let tweak_value = TapTweakHash::from_key_and_tweak(pubkey, merkle_root).into_inner();
-        self.tweak_add_assign(secp, &tweak_value).expect("Tap tweak failed");
-        TweakedKeyPair(self)
+    fn tap_tweak<C: Verification>(self, secp: &Secp256k1<C>, merkle_root: Option<TapBranchHash>) -> TweakedKeyPair {
+        let (pubkey, _parity) = crate::XOnlyPublicKey::from_keypair(&self);
+        let tweak = TapTweakHash::from_key_and_tweak(pubkey, merkle_root).to_scalar();
+        let tweaked = self.add_xonly_tweak(secp, &tweak).expect("Tap tweak failed");
+        TweakedKeyPair(tweaked)
     }
 
     fn dangerous_assume_tweaked(self) -> TweakedKeyPair {

src/util/taproot.rs

@@ -18,7 +18,7 @@
 
 use crate::prelude::*;
 use crate::io;
-use secp256k1::{self, Secp256k1};
+use secp256k1::{self, Secp256k1, Scalar};
 
 use core::fmt;
 use core::cmp::Reverse;
@@ -89,6 +89,11 @@ impl TapTweakHash {
         }
         TapTweakHash::from_engine(eng)
     }
+
+    /// Converts a `TapTweakHash` into a `Scalar` ready for use with key tweaking API.
+    pub fn to_scalar(&self) -> Scalar {
+        Scalar::from_be_bytes(self.into_inner()).expect("TODO: handle this error")
+    }
 }
 
 impl TapLeafHash {
@@ -818,12 +823,12 @@ impl ControlBlock {
             );
         }
         // compute the taptweak
-        let tweak = TapTweakHash::from_key_and_tweak(self.internal_key, Some(curr_hash));
+        let tweak = TapTweakHash::from_key_and_tweak(self.internal_key, Some(curr_hash)).to_scalar();
         self.internal_key.tweak_add_check(
             secp,
             &output_key,
             self.output_key_parity,
-            tweak.into_inner(),
+            tweak,
         )
     }
 }