Merge pull request #308 from LNP-BP/extrakeys/keypair-ser

Adding KeyPair::serialize_sec. Closes #298

Author: apoelstra

Cargo.toml

@@ -7,7 +7,7 @@ license = "CC0-1.0"
 homepage = "https://github.com/rust-bitcoin/rust-secp256k1/"
 repository = "https://github.com/rust-bitcoin/rust-secp256k1/"
 documentation = "https://docs.rs/secp256k1/"
-description = "Rust bindings for Pieter Wuille's `libsecp256k1` library. Implements ECDSA for the SECG elliptic curve group secp256k1 and related utilities."
+description = "Rust wrapper library for Pieter Wuille's `libsecp256k1`. Implements ECDSA and BIP 340 signatures for the SECG elliptic curve group secp256k1 and related utilities."
 keywords = [ "crypto", "ECDSA", "secp256k1", "libsecp256k1", "bitcoin" ]
 readme = "README.md"
 autoexamples = false # Remove when edition 2018 https://github.com/rust-lang/cargo/issues/5330

src/key.rs

@@ -27,7 +27,7 @@ use constants;
 use ffi::{self, CPtr};
 
 /// Secret 256-bit key used as `x` in an ECDSA signature
-pub struct SecretKey(pub(crate) [u8; constants::SECRET_KEY_SIZE]);
+pub struct SecretKey([u8; constants::SECRET_KEY_SIZE]);
 impl_array_newtype!(SecretKey, u8, constants::SECRET_KEY_SIZE);
 impl_pretty_debug!(SecretKey);
 
@@ -66,7 +66,7 @@ pub const ONE_KEY: SecretKey = SecretKey([0, 0, 0, 0, 0, 0, 0, 0,
 /// A Secp256k1 public key, used for verification of signatures
 #[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
 #[repr(transparent)]
-pub struct PublicKey(pub(crate) ffi::PublicKey);
+pub struct PublicKey(ffi::PublicKey);
 
 impl fmt::LowerHex for PublicKey {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
@@ -149,6 +149,21 @@ impl SecretKey {
         }
     }
 
+    /// Creates a new secret key using data from BIP-340 [`::schnorrsig::KeyPair`]
+    #[inline]
+    pub fn from_keypair(keypair: &::schnorrsig::KeyPair) -> Self {
+        let mut sk = [0; constants::SECRET_KEY_SIZE];
+        unsafe {
+            let ret = ffi::secp256k1_keypair_sec(
+                ffi::secp256k1_context_no_precomp,
+                sk.as_mut_c_ptr(),
+                keypair.as_ptr()
+            );
+            debug_assert_eq!(ret, 1);
+        }
+        SecretKey(sk)
+    }
+
     #[inline]
     /// Negates one secret key.
     pub fn negate_assign(
@@ -290,6 +305,21 @@ impl PublicKey {
         }
     }
 
+    /// Creates a new compressed public key key using data from BIP-340 [`::schnorrsig::KeyPair`]
+    #[inline]
+    pub fn from_keypair(keypair: &::schnorrsig::KeyPair) -> Self {
+        unsafe {
+            let mut pk = ffi::PublicKey::new();
+            let ret = ffi::secp256k1_keypair_pub(
+                ffi::secp256k1_context_no_precomp,
+                &mut pk,
+                keypair.as_ptr()
+            );
+            debug_assert_eq!(ret, 1);
+            PublicKey(pk)
+        }
+    }
+
     #[inline]
     /// Serialize the key as a byte-encoded pair of values. In compressed form
     /// the y-coordinate is represented by only a single bit, as x determines

src/schnorrsig.rs

@@ -211,6 +211,12 @@ impl KeyPair {
         }
     }
 
+    /// Serialize the key pair as a secret key byte value
+    #[inline]
+    pub fn serialize_secret(&self) -> [u8; constants::SECRET_KEY_SIZE] {
+        *SecretKey::from_keypair(self).as_ref()
+    }
+
     /// Tweak a keypair by adding the given tweak to the secret key and updating the
     /// public key accordingly.
     /// Will return an error if the resulting key would be invalid or if
@@ -450,35 +456,31 @@ impl<'de> ::serde::Deserialize<'de> for PublicKey {
     }
 }
 
-impl SecretKey {
-    /// Creates a new secret key using data from BIP-340 [`KeyPair`]
-    pub fn from_keypair<V: Verification>(secp: &Secp256k1<V>, keypair: &KeyPair) -> Self {
-        let mut sk = [0; constants::SECRET_KEY_SIZE];
-        unsafe {
-            let ret = ffi::secp256k1_keypair_sec(
-                secp.ctx,
-                sk.as_mut_c_ptr(),
-                keypair.as_ptr()
-            );
-            debug_assert_eq!(ret, 1);
-        }
-        SecretKey(sk)
+impl From<KeyPair> for SecretKey {
+    #[inline]
+    fn from(pair: KeyPair) -> Self {
+        SecretKey::from_keypair(&pair)
     }
 }
 
-impl ::key::PublicKey {
-    /// Creates a new compressed public key key using data from BIP-340 [`KeyPair`]
-    pub fn from_keypair<C: Signing>(secp: &Secp256k1<C>, keypair: &KeyPair) -> Self {
-        unsafe {
-            let mut pk = ffi::PublicKey::new();
-            let ret = ffi::secp256k1_keypair_pub(
-                secp.ctx,
-                &mut pk,
-                keypair.as_ptr()
-            );
-            debug_assert_eq!(ret, 1);
-            ::key::PublicKey(pk)
-        }
+impl<'a> From<&'a KeyPair> for SecretKey {
+    #[inline]
+    fn from(pair: &'a KeyPair) -> Self {
+        SecretKey::from_keypair(pair)
+    }
+}
+
+impl From<KeyPair> for ::key::PublicKey {
+    #[inline]
+    fn from(pair: KeyPair) -> Self {
+        ::key::PublicKey::from_keypair(&pair)
+    }
+}
+
+impl<'a> From<&'a KeyPair> for ::key::PublicKey {
+    #[inline]
+    fn from(pair: &'a KeyPair) -> Self {
+        ::key::PublicKey::from_keypair(pair)
     }
 }
 
@@ -728,9 +730,9 @@ mod tests {
         let secp = Secp256k1::new();
         let sk_str = "688C77BC2D5AAFF5491CF309D4753B732135470D05B7B2CD21ADD0744FE97BEF";
         let keypair = KeyPair::from_seckey_str(&secp, sk_str).unwrap();
-        let sk = SecretKey::from_keypair(&secp, &keypair);
+        let sk = SecretKey::from_keypair(&keypair);
         assert_eq!(SecretKey::from_str(sk_str).unwrap(), sk);
-        let pk = ::key::PublicKey::from_keypair(&secp, &keypair);
+        let pk = ::key::PublicKey::from_keypair(&keypair);
         assert_eq!(::key::PublicKey::from_secret_key(&secp, &sk), pk);
         let xpk = PublicKey::from_keypair(&secp, &keypair);
         assert_eq!(PublicKey::from(pk), xpk);