Add schnorrsig module

src/constants.rs

@@ -34,6 +34,15 @@ pub const MAX_SIGNATURE_SIZE: usize = 72;
 /// The maximum size of a compact signature
 pub const COMPACT_SIGNATURE_SIZE: usize = 64;
 
+/// Size of a Schnorr signature
+pub const SCHNORRSIG_SIGNATURE_SIZE: usize = 64;
+
+/// Size of a Schnorr public key
+pub const SCHNORRSIG_PUBLIC_KEY_SIZE: usize = 32;
+
+/// Size of a key pair
+pub const KEY_PAIR_SIZE: usize = 96;
+
 /// The Prime for the secp256k1 field element.
 pub const FIELD_SIZE: [u8; 32] = [
     0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,

src/lib.rs

@@ -142,6 +142,7 @@ mod context;
 pub mod constants;
 pub mod ecdh;
 pub mod key;
+pub mod schnorrsig;
 #[cfg(feature = "recovery")]
 pub mod recovery;
 

src/macros.rs

@@ -67,7 +67,7 @@ macro_rules! serde_impl(
 
                 if d.is_human_readable() {
                     let sl: &str = ::serde::Deserialize::deserialize(d)?;
-                    SecretKey::from_str(sl).map_err(D::Error::custom)
+                    $t::from_str(sl).map_err(D::Error::custom)
                 } else {
                     let sl: &[u8] = ::serde::Deserialize::deserialize(d)?;
                     if sl.len() != $len {

src/schnorrsig.rs

@@ -0,0 +1,710 @@
+//! # schnorrsig
+//! Support for Schnorr signatures.
+//!
+
+#[cfg(any(test, feature = "rand-std"))]
+use rand::thread_rng;
+#[cfg(any(test, feature = "rand"))]
+use rand::{CryptoRng, Rng};
+
+use super::Error::{InvalidPublicKey, InvalidSecretKey, InvalidSignature};
+use super::{from_hex, Error};
+use core::{fmt, ptr, str};
+use ffi::{self, CPtr};
+use {constants, Secp256k1};
+use {Message, Signing, Verification};
+
+/// Represents a Schnorr signature.
+pub struct Signature([u8; constants::SCHNORRSIG_SIGNATURE_SIZE]);
+impl_array_newtype!(Signature, u8, constants::SCHNORRSIG_SIGNATURE_SIZE);
+impl_pretty_debug!(Signature);
+serde_impl!(Signature, constants::SCHNORRSIG_SIGNATURE_SIZE);
+
+impl fmt::LowerHex for Signature {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        for ch in &self.0[..] {
+            write!(f, "{:02x}", ch)?;
+        }
+        Ok(())
+    }
+}
+
+impl fmt::Display for Signature {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::LowerHex::fmt(self, f)
+    }
+}
+
+impl str::FromStr for Signature {
+    type Err = Error;
+    fn from_str(s: &str) -> Result<Signature, Error> {
+        let mut res = [0; constants::SCHNORRSIG_SIGNATURE_SIZE];
+        match from_hex(s, &mut res) {
+            Ok(constants::SCHNORRSIG_SIGNATURE_SIZE) => {
+                Signature::from_slice(&res[0..constants::SCHNORRSIG_SIGNATURE_SIZE])
+            }
+            _ => Err(Error::InvalidSignature),
+        }
+    }
+}
+
+/// Opaque data structure that holds a keypair consisting of a secret and a public key.
+#[derive(Copy, Clone, PartialEq, Eq, Debug, PartialOrd, Ord, Hash)]
+pub struct KeyPair(ffi::KeyPair);
+
+/// A Schnorr public key, used for verification of Schnorr signatures
+#[derive(Copy, Clone, PartialEq, Eq, Debug, PartialOrd, Ord, Hash)]
+pub struct PublicKey(ffi::XOnlyPublicKey);
+
+impl fmt::LowerHex for PublicKey {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let ser = self.serialize();
+        for ch in &ser[..] {
+            write!(f, "{:02x}", *ch)?;
+        }
+        Ok(())
+    }
+}
+
+impl fmt::Display for PublicKey {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::LowerHex::fmt(self, f)
+    }
+}
+
+impl str::FromStr for PublicKey {
+    type Err = Error;
+    fn from_str(s: &str) -> Result<PublicKey, Error> {
+        let mut res = [0; constants::SCHNORRSIG_PUBLIC_KEY_SIZE];
+        match from_hex(s, &mut res) {
+            Ok(constants::SCHNORRSIG_PUBLIC_KEY_SIZE) => {
+                PublicKey::from_slice(&res[0..constants::SCHNORRSIG_PUBLIC_KEY_SIZE])
+            }
+            _ => Err(InvalidPublicKey),
+        }
+    }
+}
+
+impl Signature {
+    /// Creates a Signature directly from a slice
+    #[inline]
+    pub fn from_slice(data: &[u8]) -> Result<Signature, Error> {
+        match data.len() {
+            constants::SCHNORRSIG_SIGNATURE_SIZE => {
+                let mut ret = [0; constants::SCHNORRSIG_SIGNATURE_SIZE];
+                ret[..].copy_from_slice(data);
+                Ok(Signature(ret))
+            }
+            _ => Err(InvalidSignature),
+        }
+    }
+}
+
+impl KeyPair {
+    /// Obtains a raw const pointer suitable for use with FFI functions
+    #[inline]
+    pub fn as_ptr(&self) -> *const ffi::KeyPair {
+        &self.0 as *const _
+    }
+
+    /// Obtains a raw mutable pointer suitable for use with FFI functions
+    #[inline]
+    pub fn as_mut_ptr(&mut self) -> *mut ffi::KeyPair {
+        &mut self.0 as *mut _
+    }
+
+    /// Creates a Schnorr KeyPair directly from a secret key slice
+    #[inline]
+    pub fn from_seckey_slice<C: Signing>(
+        secp: &Secp256k1<C>,
+        data: &[u8],
+    ) -> Result<KeyPair, Error> {
+        if data.is_empty() || data.len() != constants::SECRET_KEY_SIZE {
+            return Err(InvalidPublicKey);
+        }
+
+        let mut kp = ffi::KeyPair::new();
+        unsafe {
+            if ffi::secp256k1_keypair_create(secp.ctx, &mut kp, data.as_c_ptr()) == 1 {
+                Ok(KeyPair(kp))
+            } else {
+                Err(InvalidSecretKey)
+            }
+        }
+    }
+
+    /// Creates a Schnorr KeyPair directly from a secret key string
+    #[inline]
+    pub fn from_seckey_str<C: Signing>(secp: &Secp256k1<C>, s: &str) -> Result<KeyPair, Error> {
+        let mut res = [0; constants::SECRET_KEY_SIZE];
+        match from_hex(s, &mut res) {
+            Ok(constants::SECRET_KEY_SIZE) => {
+                KeyPair::from_seckey_slice(secp, &res[0..constants::SECRET_KEY_SIZE])
+            }
+            _ => Err(InvalidPublicKey),
+        }
+    }
+
+    /// Creates a new random secret key. Requires compilation with the "rand" feature.
+    #[inline]
+    #[cfg(any(test, feature = "rand"))]
+    pub fn new<R: Rng + ?Sized, C: Signing>(secp: &Secp256k1<C>, rng: &mut R) -> KeyPair {
+        let mut random_32_bytes = || {
+            let mut ret = [0u8; 32];
+            rng.fill_bytes(&mut ret);
+            ret
+        };
+        let mut data = random_32_bytes();
+        let mut keypair = ffi::KeyPair::new();
+        unsafe {
+            while ffi::secp256k1_keypair_create(secp.ctx, &mut keypair, data.as_c_ptr()) == 0 {
+                data = random_32_bytes();
+            }
+        }
+        KeyPair(keypair)
+    }
+
+    /// 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
+    /// the tweak was not a 32-byte length slice.
+    #[inline]
+    pub fn add_assign<C: Verification>(
+        &mut self,
+        secp: &Secp256k1<C>,
+        tweak: &[u8],
+    ) -> Result<(), Error> {
+        if tweak.len() != 32 {
+            return Err(Error::InvalidTweak);
+        }
+
+        unsafe {
+            let err = ffi::secp256k1_keypair_xonly_tweak_add(
+                secp.ctx,
+                &mut self.0 as *mut _,
+                tweak.as_c_ptr(),
+            );
+
+            return if err == 1 {
+                Ok(())
+            } else {
+                Err(Error::InvalidTweak)
+            };
+        }
+    }
+}
+
+impl PublicKey {
+    /// Obtains a raw const pointer suitable for use with FFI functions
+    #[inline]
+    pub fn as_ptr(&self) -> *const ffi::XOnlyPublicKey {
+        &self.0 as *const _
+    }
+
+    /// Obtains a raw mutable pointer suitable for use with FFI functions
+    #[inline]
+    pub fn as_mut_ptr(&mut self) -> *mut ffi::XOnlyPublicKey {
+        &mut self.0 as *mut _
+    }
+
+    /// Creates a new Schnorr public key from a Schnorr key pair
+    #[inline]
+    pub fn from_keypair<C: Signing>(secp: &Secp256k1<C>, keypair: &KeyPair) -> PublicKey {
+        let mut xonly_pk = ffi::XOnlyPublicKey::new();
+        let mut pk_parity = 0;
+        unsafe {
+            let ret = ffi::secp256k1_keypair_xonly_pub(
+                secp.ctx,
+                &mut xonly_pk,
+                &mut pk_parity,
+                keypair.as_ptr(),
+            );
+            debug_assert_eq!(ret, 1);
+        }
+        PublicKey(xonly_pk)
+    }
+
+    /// Creates a Schnorr public key directly from a slice
+    #[inline]
+    pub fn from_slice(data: &[u8]) -> Result<PublicKey, Error> {
+        if data.is_empty() || data.len() != constants::SCHNORRSIG_PUBLIC_KEY_SIZE {
+            return Err(InvalidPublicKey);
+        }
+
+        let mut pk = ffi::XOnlyPublicKey::new();
+        unsafe {
+            if ffi::secp256k1_xonly_pubkey_parse(
+                ffi::secp256k1_context_no_precomp,
+                &mut pk,
+                data.as_c_ptr(),
+            ) == 1
+            {
+                Ok(PublicKey(pk))
+            } else {
+                Err(InvalidPublicKey)
+            }
+        }
+    }
+
+    #[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
+    /// it up to one bit.
+    pub fn serialize(&self) -> [u8; constants::SCHNORRSIG_PUBLIC_KEY_SIZE] {
+        let mut ret = [0; constants::SCHNORRSIG_PUBLIC_KEY_SIZE];
+
+        unsafe {
+            let err = ffi::secp256k1_xonly_pubkey_serialize(
+                ffi::secp256k1_context_no_precomp,
+                ret.as_mut_c_ptr(),
+                self.as_c_ptr(),
+            );
+            debug_assert_eq!(err, 1);
+        }
+        ret
+    }
+
+    /// Tweak a schnorrsig PublicKey by adding the generator multiplied with the given tweak to it.
+    /// Will return an error if the resulting key would be invalid or if
+    /// the tweak was not a 32-byte length slice.
+    pub fn add_assign<V: Verification>(
+        &mut self,
+        secp: &Secp256k1<V>,
+        tweak: &[u8],
+    ) -> Result<(), Error> {
+        if tweak.len() != 32 {
+            return Err(Error::InvalidTweak);
+        }
+
+        unsafe {
+            let mut pubkey = ffi::PublicKey::new();
+            let mut err = ffi::secp256k1_xonly_pubkey_tweak_add(
+                secp.ctx,
+                &mut pubkey,
+                self.as_c_ptr(),
+                tweak.as_c_ptr(),
+            );
+
+            if err != 1 {
+                return Err(Error::InvalidTweak);
+            }
+
+            err = ffi::secp256k1_xonly_pubkey_from_pubkey(
+                secp.ctx,
+                &mut self.0 as *mut _,
+                ptr::null_mut(),
+                &pubkey,
+            );
+
+            return if err == 0 {
+                Err(Error::InvalidPublicKey)
+            } else {
+                Ok(())
+            };
+        }
+    }
+}
+
+impl CPtr for PublicKey {
+    type Target = ffi::XOnlyPublicKey;
+    fn as_c_ptr(&self) -> *const Self::Target {
+        self.as_ptr()
+    }
+
+    fn as_mut_c_ptr(&mut self) -> *mut Self::Target {
+        self.as_mut_ptr()
+    }
+}
+
+/// Creates a new Schnorr public key from a FFI x-only public key
+impl From<ffi::XOnlyPublicKey> for PublicKey {
+    #[inline]
+    fn from(pk: ffi::XOnlyPublicKey) -> PublicKey {
+        PublicKey(pk)
+    }
+}
+
+serde_impl_from_slice!(PublicKey);
+
+impl<C: Signing> Secp256k1<C> {
+    fn schnorrsig_sign_helper(
+        &self,
+        msg: &Message,
+        keypair: &KeyPair,
+        nonce_data: *const ffi::types::c_void,
+    ) -> Result<Signature, Error> {
+        unsafe {
+            let mut sig = [0u8; constants::SCHNORRSIG_SIGNATURE_SIZE];
+            assert_eq!(
+                1,
+                ffi::secp256k1_schnorrsig_sign(
+                    self.ctx,
+                    sig.as_mut_c_ptr(),
+                    msg.as_c_ptr(),
+                    keypair.as_ptr(),
+                    ffi::secp256k1_nonce_function_bip340,
+                    nonce_data
+                )
+            );
+
+            Ok(Signature(sig))
+        }
+    }
+
+    /// Create a schnorr signature internally using the ThreadRng random number
+    /// generator to generate the auxiliary random data.
+    /// Requires compilation with "rand-std" feature.
+    #[cfg(any(test, feature = "rand-std"))]
+    pub fn schnorrsig_sign(&self, msg: &Message, keypair: &KeyPair) -> Result<Signature, Error> {
+        let mut rng = thread_rng();
+        self.schnorrsig_sign_with_rng(msg, keypair, &mut rng)
+    }
+
+    /// Create a schnorr signature without using any auxiliary random data.
+    pub fn schnorrsig_sign_no_aux_rand(
+        &self,
+        msg: &Message,
+        keypair: &KeyPair,
+    ) -> Result<Signature, Error> {
+        self.schnorrsig_sign_helper(msg, keypair, ptr::null())
+    }
+
+    /// Create a Schnorr signature using the given auxiliary random data.
+    pub fn schnorrsig_sign_with_aux_rand(
+        &self,
+        msg: &Message,
+        keypair: &KeyPair,
+        aux_rand: &[u8; 32],
+    ) -> Result<Signature, Error> {
+        self.schnorrsig_sign_helper(
+            msg,
+            keypair,
+            aux_rand.as_c_ptr() as *const ffi::types::c_void,
+        )
+    }
+
+    /// Create a schnorr signature using the given random number generator to
+    /// generate the auxiliary random data. Requires compilation with "rand"
+    /// feature.
+    #[cfg(any(test, feature = "rand"))]
+    pub fn schnorrsig_sign_with_rng<R: Rng + CryptoRng>(
+        &self,
+        msg: &Message,
+        keypair: &KeyPair,
+        rng: &mut R,
+    ) -> Result<Signature, Error> {
+        let mut aux = [0u8; 32];
+        rng.fill_bytes(&mut aux);
+        self.schnorrsig_sign_helper(msg, keypair, aux.as_c_ptr() as *const ffi::types::c_void)
+    }
+
+    /// Verify a Schnorr signature.
+    pub fn schnorrsig_verify(
+        &self,
+        sig: &Signature,
+        msg: &Message,
+        pubkey: &PublicKey,
+    ) -> Result<(), Error> {
+        unsafe {
+            let ret = ffi::secp256k1_schnorrsig_verify(
+                self.ctx,
+                sig.as_c_ptr(),
+                msg.as_c_ptr(),
+                pubkey.as_c_ptr(),
+            );
+
+            return if ret == 1 {
+                Ok(())
+            } else {
+                Err(Error::InvalidSignature)
+            };
+        }
+    }
+
+    /// Generates a random Schnorr KeyPair and its associated Schnorr PublicKey.
+    /// Convenience function for `schnorrsig::KeyPair::new` and
+    /// `schnorrsig::PublicKey::from_keypair`; call those functions directly for
+    /// batch key generation. Requires a signing-capable context. Requires compilation
+    /// with the "rand" feature.
+    #[inline]
+    #[cfg(any(test, feature = "rand"))]
+    pub fn generate_schnorrsig_keypair<R: Rng + ?Sized>(
+        &self,
+        rng: &mut R,
+    ) -> (KeyPair, PublicKey) {
+        let sk = KeyPair::new(self, rng);
+        let pubkey = PublicKey::from_keypair(self, &sk);
+        (sk, pubkey)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::super::Error::InvalidPublicKey;
+    use super::super::{constants, from_hex, All, Message, Secp256k1};
+    use super::{KeyPair, PublicKey, Signature};
+    use rand::{rngs::ThreadRng, thread_rng, Error, ErrorKind, RngCore};
+    use rand_core::impls;
+    use std::iter;
+    use std::str::FromStr;
+
+    macro_rules! hex_32 {
+        ($hex:expr) => {{
+            let mut result = [0; 32];
+            from_hex($hex, &mut result).expect("valid hex string");
+            result
+        }};
+    }
+
+    fn test_schnorrsig_sign_helper(
+        sign: fn(&Secp256k1<All>, &Message, &KeyPair, &mut ThreadRng) -> Signature,
+    ) {
+        let secp = Secp256k1::new();
+
+        let mut rng = thread_rng();
+        let (seckey, pubkey) = secp.generate_schnorrsig_keypair(&mut rng);
+        let mut msg = [0; 32];
+
+        for _ in 0..100 {
+            rng.fill_bytes(&mut msg);
+            let msg = Message::from_slice(&msg).unwrap();
+
+            let sig = sign(&secp, &msg, &seckey, &mut rng);
+
+            assert!(secp.schnorrsig_verify(&sig, &msg, &pubkey).is_ok());
+        }
+    }
+
+    #[test]
+    fn test_schnorrsig_sign_with_aux_rand_verify() {
+        test_schnorrsig_sign_helper(|secp, msg, seckey, rng| {
+            let mut aux_rand = [0; 32];
+            rng.fill_bytes(&mut aux_rand);
+            secp.schnorrsig_sign_with_aux_rand(msg, seckey, &aux_rand)
+                .unwrap()
+        })
+    }
+
+    #[test]
+    fn test_schnorrsig_sign_with_rng_verify() {
+        test_schnorrsig_sign_helper(|secp, msg, seckey, mut rng| {
+            secp.schnorrsig_sign_with_rng(msg, seckey, &mut rng)
+                .unwrap()
+        })
+    }
+
+    #[test]
+    fn test_schnorrsig_sign_verify() {
+        test_schnorrsig_sign_helper(|secp, msg, seckey, _| {
+            secp.schnorrsig_sign(msg, seckey).unwrap()
+        })
+    }
+
+    #[test]
+    fn test_schnorrsig_sign_no_aux_rand_verify() {
+        test_schnorrsig_sign_helper(|secp, msg, seckey, _| {
+            secp.schnorrsig_sign_no_aux_rand(msg, seckey).unwrap()
+        })
+    }
+
+    #[test]
+    fn test_schnorrsig_sign() {
+        let secp = Secp256k1::new();
+
+        let hex_msg = hex_32!("E48441762FB75010B2AA31A512B62B4148AA3FB08EB0765D76B252559064A614");
+        let msg = Message::from_slice(&hex_msg).unwrap();
+        let sk = KeyPair::from_seckey_str(
+            &secp,
+            "688C77BC2D5AAFF5491CF309D4753B732135470D05B7B2CD21ADD0744FE97BEF",
+        )
+        .unwrap();
+        let aux_rand: [u8; 32] =
+            hex_32!("02CCE08E913F22A36C5648D6405A2C7C50106E7AA2F1649E381C7F09D16B80AB");
+        let expected_sig = Signature::from_str("6470FD1303DDA4FDA717B9837153C24A6EAB377183FC438F939E0ED2B620E9EE5077C4A8B8DCA28963D772A94F5F0DDF598E1C47C137F91933274C7C3EDADCE8").unwrap();
+
+        let sig = secp
+            .schnorrsig_sign_with_aux_rand(&msg, &sk, &aux_rand)
+            .unwrap();
+
+        assert_eq!(expected_sig, sig);
+    }
+
+    #[test]
+    fn test_schnorrsig_verify() {
+        let secp = Secp256k1::new();
+
+        let hex_msg = hex_32!("E48441762FB75010B2AA31A512B62B4148AA3FB08EB0765D76B252559064A614");
+        let msg = Message::from_slice(&hex_msg).unwrap();
+        let sig = Signature::from_str("6470FD1303DDA4FDA717B9837153C24A6EAB377183FC438F939E0ED2B620E9EE5077C4A8B8DCA28963D772A94F5F0DDF598E1C47C137F91933274C7C3EDADCE8").unwrap();
+        let pubkey =
+            PublicKey::from_str("B33CC9EDC096D0A83416964BD3C6247B8FECD256E4EFA7870D2C854BDEB33390")
+                .unwrap();
+
+        assert!(secp.schnorrsig_verify(&sig, &msg, &pubkey).is_ok());
+    }
+
+    #[test]
+    fn pubkey_from_slice() {
+        assert_eq!(PublicKey::from_slice(&[]), Err(InvalidPublicKey));
+        assert_eq!(PublicKey::from_slice(&[1, 2, 3]), Err(InvalidPublicKey));
+        let pk = PublicKey::from_slice(&[
+            0xB3, 0x3C, 0xC9, 0xED, 0xC0, 0x96, 0xD0, 0xA8, 0x34, 0x16, 0x96, 0x4B, 0xD3, 0xC6,
+            0x24, 0x7B, 0x8F, 0xEC, 0xD2, 0x56, 0xE4, 0xEF, 0xA7, 0x87, 0x0D, 0x2C, 0x85, 0x4B,
+            0xDE, 0xB3, 0x33, 0x90,
+        ]);
+        assert!(pk.is_ok());
+    }
+
+    #[test]
+    fn pubkey_serialize_roundtrip() {
+        let secp = Secp256k1::new();
+        let (_, pubkey) = secp.generate_schnorrsig_keypair(&mut thread_rng());
+        let ser = pubkey.serialize();
+        let pubkey2 = PublicKey::from_slice(&ser).unwrap();
+        assert_eq!(pubkey, pubkey2);
+    }
+
+    #[test]
+    fn test_pubkey_from_bad_slice() {
+        // Bad sizes
+        assert_eq!(
+            PublicKey::from_slice(&[0; constants::SCHNORRSIG_PUBLIC_KEY_SIZE - 1]),
+            Err(InvalidPublicKey)
+        );
+        assert_eq!(
+            PublicKey::from_slice(&[0; constants::SCHNORRSIG_PUBLIC_KEY_SIZE + 1]),
+            Err(InvalidPublicKey)
+        );
+
+        // Bad parse
+        assert_eq!(
+            PublicKey::from_slice(&[0xff; constants::SCHNORRSIG_PUBLIC_KEY_SIZE]),
+            Err(InvalidPublicKey)
+        );
+        assert_eq!(
+            PublicKey::from_slice(&[0x55; constants::SCHNORRSIG_PUBLIC_KEY_SIZE]),
+            Err(InvalidPublicKey)
+        );
+        assert_eq!(PublicKey::from_slice(&[]), Err(InvalidPublicKey));
+    }
+
+    #[test]
+    fn test_pubkey_display_output() {
+        let secp = Secp256k1::new();
+        static SK_BYTES: [u8; 32] = [
+            0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05,
+            0x06, 0x07, 0xff, 0xff, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00, 0x63, 0x63, 0x63, 0x63,
+            0x63, 0x63, 0x63, 0x63,
+        ];
+
+        let s = Secp256k1::signing_only();
+        let sk = KeyPair::from_seckey_slice(&secp, &SK_BYTES).expect("sk");
+        let pk = PublicKey::from_keypair(&s, &sk);
+
+        assert_eq!(
+            pk.to_string(),
+            "18845781f631c48f1c9709e23092067d06837f30aa0cd0544ac887fe91ddd166"
+        );
+        assert_eq!(
+            PublicKey::from_str("18845781f631c48f1c9709e23092067d06837f30aa0cd0544ac887fe91ddd166")
+                .unwrap(),
+            pk
+        );
+
+        assert!(PublicKey::from_str(
+            "00000000000000000000000000000000000000000000000000000000000000000"
+        )
+        .is_err());
+        assert!(PublicKey::from_str(
+            "18845781f631c48f1c9709e23092067d06837f30aa0cd0544ac887fe91ddd16601"
+        )
+        .is_err());
+        assert!(PublicKey::from_str(
+            "18845781f631c48f1c9709e23092067d06837f30aa0cd0544ac887fe91ddd16"
+        )
+        .is_err());
+        assert!(PublicKey::from_str(
+            "18845781f631c48f1c9709e23092067d06837f30aa0cd0544ac887fe91ddd1"
+        )
+        .is_err());
+        assert!(PublicKey::from_str(
+            "xx18845781f631c48f1c9709e23092067d06837f30aa0cd0544ac887fe91ddd1"
+        )
+        .is_err());
+
+        let long_str: String = iter::repeat('a').take(1024 * 1024).collect();
+        assert!(PublicKey::from_str(&long_str).is_err());
+    }
+
+    #[test]
+    fn test_pubkey_serialize() {
+        struct DumbRng(u32);
+        impl RngCore for DumbRng {
+            fn next_u32(&mut self) -> u32 {
+                self.0 = self.0.wrapping_add(1);
+                self.0
+            }
+            fn next_u64(&mut self) -> u64 {
+                self.next_u32() as u64
+            }
+            fn try_fill_bytes(&mut self, _dest: &mut [u8]) -> Result<(), Error> {
+                Err(Error::new(ErrorKind::Unavailable, "not implemented"))
+            }
+
+            fn fill_bytes(&mut self, dest: &mut [u8]) {
+                impls::fill_bytes_via_next(self, dest);
+            }
+        }
+
+        let s = Secp256k1::new();
+        let (_, pubkey) = s.generate_schnorrsig_keypair(&mut DumbRng(0));
+        assert_eq!(
+            &pubkey.serialize()[..],
+            &[
+                124, 121, 49, 14, 253, 63, 197, 50, 39, 194, 107, 17, 193, 219, 108, 154, 126, 9,
+                181, 248, 2, 12, 149, 233, 198, 71, 149, 134, 250, 184, 154, 229
+            ][..]
+        );
+    }
+
+    #[cfg(feature = "serde")]
+    #[test]
+    fn test_signature_serde() {
+        use serde_test::{assert_tokens, Configure, Token};
+
+        let s = Secp256k1::new();
+
+        let msg = Message::from_slice(&[1; 32]).unwrap();
+        let keypair = KeyPair::from_seckey_slice(&s, &[2; 32]).unwrap();
+        let aux = [3; 32];
+        let sig = s
+            .schnorrsig_sign_with_aux_rand(&msg, &keypair, &aux)
+            .unwrap();
+        static SIG_BYTES: [u8; constants::SCHNORRSIG_SIGNATURE_SIZE] = [
+            0x14, 0xd0, 0xbf, 0x1a, 0x89, 0x53, 0x50, 0x6f, 0xb4, 0x60, 0xf5, 0x8b, 0xe1, 0x41,
+            0xaf, 0x76, 0x7f, 0xd1, 0x12, 0x53, 0x5f, 0xb3, 0x92, 0x2e, 0xf2, 0x17, 0x30, 0x8e,
+            0x2c, 0x26, 0x70, 0x6f, 0x1e, 0xeb, 0x43, 0x2b, 0x3d, 0xba, 0x9a, 0x01, 0x08, 0x2f,
+            0x9e, 0x4d, 0x4e, 0xf5, 0x67, 0x8a, 0xd0, 0xd9, 0xd5, 0x32, 0xc0, 0xdf, 0xa9, 0x07,
+            0xb5, 0x68, 0x72, 0x2d, 0x0b, 0x01, 0x19, 0xba,
+        ];
+        static SIG_STR: &'static str = "\
+            14d0bf1a8953506fb460f58be141af767fd112535fb3922ef217308e2c26706f1eeb432b3dba9a01082f9e4d4ef5678ad0d9d532c0dfa907b568722d0b0119ba\
+        ";
+
+        assert_tokens(&sig.compact(), &[Token::BorrowedBytes(&SIG_BYTES[..])]);
+        assert_tokens(&sig.readable(), &[Token::BorrowedStr(SIG_STR)]);
+    }
+    #[test]
+    fn test_addition() {
+        let s = Secp256k1::new();
+
+        for _ in 0..10 {
+            let mut tweak = [0u8; 32];
+            thread_rng().fill_bytes(&mut tweak);
+            let (mut kp, mut pk) = s.generate_schnorrsig_keypair(&mut thread_rng());
+            kp.add_assign(&s, &tweak).expect("Tweak error");
+            pk.add_assign(&s, &tweak).expect("Tweak error");
+            assert_eq!(PublicKey::from_keypair(&s, &kp), pk);
+        }
+    }
+}