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Add convenience methods for keys #430

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merged 3 commits into from Apr 30, 2022
Merged

Add convenience methods for keys #430

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c612130
Borrow secret key
tcharding Mar 24, 2022
b4c7fa0
Let the compiler work out int size
tcharding Mar 24, 2022
f08276a
Add convenience methods for keys
tcharding Mar 24, 2022
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265 changes: 250 additions & 15 deletions src/key.rs
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Expand Up @@ -292,6 +292,31 @@ impl SecretKey {
pub fn sign_ecdsa(&self, msg: Message) -> ecdsa::Signature {
SECP256K1.sign_ecdsa(&msg, self)
}

/// Returns the [`KeyPair`] for this [`SecretKey`].
///
/// This is equivalent to using [`KeyPair::from_secret_key`].
#[inline]
pub fn keypair<C: Signing>(&self, secp: &Secp256k1<C>) -> KeyPair {
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If we use KeyPair, according to rust naming guidelines this should be key_pair, like in PublicKey/public_key

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Lol, similar to sighash. I have no preference on this one but we should be consistent, yes.

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@tcharding tcharding Mar 30, 2022 •
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Double lol, I noticed this while writing this PR too and hoped to no one else would notice because KeyPair/keypair has to be addressed in rust-secp256k1 as well, its an invasive change.

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I think the problem is that capitalization adds less visual noise than underscoring. Thus, the same API guidelines to add capital letters and underscores in practice do not work well for human eyes.

Personally I do not care if we will use KeyPair and keypair at the same time - we already doing that all around the library.

KeyPair::from_secret_key(secp, self)
}

/// Returns the [`PublicKey`] for this [`SecretKey`].
///
/// This is equivalent to using [`PublicKey::from_secret_key`].
#[inline]
pub fn public_key<C: Signing>(&self, secp: &Secp256k1<C>) -> PublicKey {
PublicKey::from_secret_key(secp, self)
}

/// Returns the [`XOnlyPublicKey`] (and it's [`Parity`]) for this [`SecretKey`].
///
/// This is equivalent to `XOnlyPublicKey::from_keypair(self.keypair(secp))`.
#[inline]
pub fn x_only_public_key<C: Signing>(&self, secp: &Secp256k1<C>) -> (XOnlyPublicKey, Parity) {
let kp = self.keypair(secp);
XOnlyPublicKey::from_keypair(&kp)
}
}

#[cfg(feature = "serde")]
Expand Down Expand Up @@ -418,6 +443,20 @@ impl PublicKey {
}
}

/// Creates a [`PublicKey`] using the key material from `pk` combined with the `parity`.
pub fn from_x_only_public_key(pk: XOnlyPublicKey, parity: Parity) -> PublicKey {
let mut buf = [0u8; 33];

// First byte of a compressed key should be `0x02 AND parity`.
buf[0] = match parity {
Parity::Even => 0x02,
Parity::Odd => 0x03,
};
buf[1..].clone_from_slice(&pk.serialize());

PublicKey::from_slice(&buf).expect("we know the buffer is valid")
}

#[inline]
/// Serializes 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.
Expand Down Expand Up @@ -589,6 +628,25 @@ impl PublicKey {
}
}
}

/// Returns the [`XOnlyPublicKey`] (and it's [`Parity`]) for this [`PublicKey`].
#[inline]
pub fn x_only_public_key(&self) -> (XOnlyPublicKey, Parity) {
let mut pk_parity = 0;
unsafe {
let mut xonly_pk = ffi::XOnlyPublicKey::new();
let ret = ffi::secp256k1_xonly_pubkey_from_pubkey(
ffi::secp256k1_context_no_precomp,
&mut xonly_pk,
&mut pk_parity,
self.as_ptr(),
);
debug_assert_eq!(ret, 1);
let parity = Parity::from_i32(pk_parity).expect("should not panic, pk_parity is 0 or 1");

(XOnlyPublicKey(xonly_pk), parity)
}
}
}

impl CPtr for PublicKey {
Expand Down Expand Up @@ -674,7 +732,7 @@ impl Ord for PublicKey {
///
/// let secp = Secp256k1::new();
/// let (secret_key, public_key) = secp.generate_keypair(&mut rand::thread_rng());
/// let key_pair = KeyPair::from_secret_key(&secp, secret_key);
/// let key_pair = KeyPair::from_secret_key(&secp, &secret_key);
/// # }
/// ```
/// [`Deserialize`]: serde::Deserialize
Expand Down Expand Up @@ -706,7 +764,7 @@ impl KeyPair {
#[inline]
pub fn from_secret_key<C: Signing>(
secp: &Secp256k1<C>,
sk: SecretKey,
sk: &SecretKey,
) -> KeyPair {
unsafe {
let mut kp = ffi::KeyPair::new();
Expand Down Expand Up @@ -866,9 +924,27 @@ impl KeyPair {
}
}

/// Gets the [XOnlyPublicKey] for this [KeyPair].
/// Returns the [`SecretKey`] for this [`KeyPair`].
///
/// This is equivalent to using [`SecretKey::from_keypair`].
#[inline]
pub fn secret_key(&self) -> SecretKey {
SecretKey::from_keypair(self)
}

/// Returns the [`PublicKey`] for this [`KeyPair`].
///
/// This is equivalent to using [`PublicKey::from_keypair`].
#[inline]
pub fn public_key(&self) -> PublicKey {
PublicKey::from_keypair(self)
}

/// Returns the [`XOnlyPublicKey`] (and it's [`Parity`]) for this [`KeyPair`].
///
/// This is equivalent to using [`XOnlyPublicKey::from_keypair`].
#[inline]
pub fn public_key(&self) -> XOnlyPublicKey {
pub fn x_only_public_key(&self) -> (XOnlyPublicKey, Parity) {
XOnlyPublicKey::from_keypair(self)
}

Expand Down Expand Up @@ -1014,9 +1090,9 @@ impl XOnlyPublicKey {
&mut self.0
}

/// Creates a new Schnorr public key from a Schnorr key pair.
/// Returns the [`XOnlyPublicKey`] (and it's [`Parity`]) for `keypair`.
#[inline]
pub fn from_keypair(keypair: &KeyPair) -> XOnlyPublicKey {
pub fn from_keypair(keypair: &KeyPair) -> (XOnlyPublicKey, Parity) {
let mut pk_parity = 0;
unsafe {
let mut xonly_pk = ffi::XOnlyPublicKey::new();
Expand All @@ -1027,7 +1103,9 @@ impl XOnlyPublicKey {
keypair.as_ptr(),
);
debug_assert_eq!(ret, 1);
XOnlyPublicKey(xonly_pk)
let parity = Parity::from_i32(pk_parity).expect("should not panic, pk_parity is 0 or 1");

(XOnlyPublicKey(xonly_pk), parity)
}
}

Expand Down Expand Up @@ -1098,7 +1176,7 @@ impl XOnlyPublicKey {
/// thread_rng().fill_bytes(&mut tweak);
///
/// let mut key_pair = KeyPair::new(&secp, &mut thread_rng());
/// let mut public_key = key_pair.public_key();
/// let (mut public_key, _parity) = key_pair.x_only_public_key();
/// public_key.tweak_add_assign(&secp, &tweak).expect("Improbable to fail with a randomly generated tweak");
/// # }
/// ```
Expand All @@ -1111,6 +1189,7 @@ impl XOnlyPublicKey {
return Err(Error::InvalidTweak);
}

let mut pk_parity = 0;
unsafe {
let mut pubkey = ffi::PublicKey::new();
let mut err = ffi::secp256k1_xonly_pubkey_tweak_add(
Expand All @@ -1123,18 +1202,17 @@ impl XOnlyPublicKey {
return Err(Error::InvalidTweak);
}

let mut parity: ::secp256k1_sys::types::c_int = 0;
err = ffi::secp256k1_xonly_pubkey_from_pubkey(
secp.ctx,
&mut self.0,
&mut parity,
&mut pk_parity,
&pubkey,
);
if err == 0 {
return Err(Error::InvalidPublicKey);
}

Parity::from_i32(parity).map_err(Into::into)
Parity::from_i32(pk_parity).map_err(Into::into)
}
}

Expand Down Expand Up @@ -1163,7 +1241,7 @@ impl XOnlyPublicKey {
/// thread_rng().fill_bytes(&mut tweak);
///
/// let mut key_pair = KeyPair::new(&secp, &mut thread_rng());
/// let mut public_key = key_pair.public_key();
/// let (mut public_key, _) = key_pair.x_only_public_key();
/// let original = public_key;
/// let parity = public_key.tweak_add_assign(&secp, &tweak).expect("Improbable to fail with a randomly generated tweak");
/// assert!(original.tweak_add_check(&secp, &public_key, parity, tweak));
Expand All @@ -1189,6 +1267,14 @@ impl XOnlyPublicKey {
err == 1
}
}

/// Returns the [`PublicKey`] for this [`XOnlyPublicKey`].
///
/// This is equivalent to using [`PublicKey::from_xonly_and_parity(self, parity)`].
#[inline]
pub fn public_key(&self, parity: Parity) -> PublicKey {
PublicKey::from_x_only_public_key(*self, parity)
}
}

/// Represents the parity passed between FFI function calls.
Expand Down Expand Up @@ -1426,7 +1512,7 @@ pub mod serde_keypair {

Ok(KeyPair::from_secret_key(
&::SECP256K1,
secret_key,
&secret_key,
))
}
}
Expand Down Expand Up @@ -1978,12 +2064,15 @@ mod test {
thread_rng().fill_bytes(&mut tweak);

let mut kp = KeyPair::new(&s, &mut thread_rng());
let mut pk = kp.public_key();
let (mut pk, _parity) = kp.x_only_public_key();

let orig_pk = pk;
kp.tweak_add_assign(&s, &tweak).expect("Tweak error");
let parity = pk.tweak_add_assign(&s, &tweak).expect("Tweak error");
assert_eq!(XOnlyPublicKey::from_keypair(&kp), pk);

let (back, _) = XOnlyPublicKey::from_keypair(&kp);

assert_eq!(back, pk);
assert!(orig_pk.tweak_add_check(&s, &pk, parity, tweak));
}
}
Expand Down Expand Up @@ -2052,4 +2141,150 @@ mod test {
assert_tokens(&sk.readable(), &[Token::Str(SK_STR)]);
assert_tokens(&sk.readable(), &[Token::String(SK_STR)]);
}

#[cfg(all(not(fuzzing), any(feature = "alloc", feature = "std")))]
fn keys() -> (SecretKey, PublicKey, KeyPair, XOnlyPublicKey) {
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,
];

static PK_BYTES: [u8; 32] = [
0x18, 0x84, 0x57, 0x81, 0xf6, 0x31, 0xc4, 0x8f,
0x1c, 0x97, 0x09, 0xe2, 0x30, 0x92, 0x06, 0x7d,
0x06, 0x83, 0x7f, 0x30, 0xaa, 0x0c, 0xd0, 0x54,
0x4a, 0xc8, 0x87, 0xfe, 0x91, 0xdd, 0xd1, 0x66
];

let mut pk_bytes = [0u8; 33];
pk_bytes[0] = 0x02; // Use positive Y co-ordinate.
pk_bytes[1..].clone_from_slice(&PK_BYTES);

let sk = SecretKey::from_slice(&SK_BYTES).expect("failed to parse sk bytes");
let pk = PublicKey::from_slice(&pk_bytes).expect("failed to create pk from iterator");
let kp = KeyPair::from_secret_key(&secp, &sk);
let xonly = XOnlyPublicKey::from_slice(&PK_BYTES).expect("failed to get xonly from slice");

(sk, pk, kp, xonly)
}

#[test]
#[cfg(all(not(fuzzing), any(feature = "alloc", feature = "std")))]
fn convert_public_key_to_xonly_public_key() {
let (_sk, pk, _kp, want) = keys();
let (got, parity) = pk.x_only_public_key();

assert_eq!(parity, Parity::Even);
assert_eq!(got, want)
}

#[test]
#[cfg(all(not(fuzzing), any(feature = "alloc", feature = "std")))]
fn convert_secret_key_to_public_key() {
let secp = Secp256k1::new();

let (sk, want, _kp, _xonly) = keys();
let got = sk.public_key(&secp);

assert_eq!(got, want)
}

#[test]
#[cfg(all(not(fuzzing), any(feature = "alloc", feature = "std")))]
fn convert_secret_key_to_x_only_public_key() {
let secp = Secp256k1::new();

let (sk, _pk, _kp, want) = keys();
let (got, parity) = sk.x_only_public_key(&secp);

assert_eq!(parity, Parity::Even);
assert_eq!(got, want)
}

#[test]
#[cfg(all(not(fuzzing), any(feature = "alloc", feature = "std")))]
fn convert_keypair_to_public_key() {
let (_sk, want, kp, _xonly) = keys();
let got = kp.public_key();

assert_eq!(got, want)
}

#[test]
#[cfg(all(not(fuzzing), any(feature = "alloc", feature = "std")))]
fn convert_keypair_to_x_only_public_key() {
let (_sk, _pk, kp, want) = keys();
let (got, parity) = kp.x_only_public_key();

assert_eq!(parity, Parity::Even);
assert_eq!(got, want)
}

// SecretKey -> KeyPair -> SecretKey
#[test]
#[cfg(all(not(fuzzing), any(feature = "alloc", feature = "std")))]
fn roundtrip_secret_key_via_keypair() {
let secp = Secp256k1::new();
let (sk, _pk, _kp, _xonly) = keys();

let kp = sk.keypair(&secp);
let back = kp.secret_key();

assert_eq!(back, sk)
}

// KeyPair -> SecretKey -> KeyPair
#[test]
#[cfg(all(not(fuzzing), any(feature = "alloc", feature = "std")))]
fn roundtrip_keypair_via_secret_key() {
let secp = Secp256k1::new();
let (_sk, _pk, kp, _xonly) = keys();

let sk = kp.secret_key();
let back = sk.keypair(&secp);

assert_eq!(back, kp)
}

// XOnlyPublicKey -> PublicKey -> XOnlyPublicKey
#[test]
#[cfg(all(not(fuzzing), any(feature = "alloc", feature = "std")))]
fn roundtrip_x_only_public_key_via_public_key() {
let (_sk, _pk, _kp, xonly) = keys();

let pk = xonly.public_key(Parity::Even);
let (back, parity) = pk.x_only_public_key();

assert_eq!(parity, Parity::Even);
assert_eq!(back, xonly)
}

// PublicKey -> XOnlyPublicKey -> PublicKey
#[test]
#[cfg(all(not(fuzzing), any(feature = "alloc", feature = "std")))]
fn roundtrip_public_key_via_x_only_public_key() {
let (_sk, pk, _kp, _xonly) = keys();

let (xonly, parity) = pk.x_only_public_key();
let back = xonly.public_key(parity);

assert_eq!(back, pk)
}

#[test]
fn public_key_from_x_only_public_key_and_odd_parity() {
let s = "18845781f631c48f1c9709e23092067d06837f30aa0cd0544ac887fe91ddd166";
let mut want = String::from("03");
want.push_str(s);

let xonly = XOnlyPublicKey::from_str(s).expect("failed to parse xonly pubkey string");
let pk = xonly.public_key(Parity::Odd);
let got = format!("{}", pk);

assert_eq!(got, want)
}
}