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Fix rerandomization seed usage #855

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Merged
merged 2 commits into from
Sep 17, 2025
Merged

Fix rerandomization seed usage #855

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0e0eb60
musig: Use secret bytes from keypair to rerandomize
tcharding Sep 17, 2025
99171f8
Don't re-randomize unnecessarily
tcharding Sep 17, 2025
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4 changes: 1 addition & 3 deletions src/ecdsa/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -377,8 +377,6 @@ pub fn sign_low_r(msg: impl Into<Message>, sk: &SecretKey) -> Signature {
#[inline]
pub fn verify(sig: &Signature, msg: impl Into<Message>, pk: &PublicKey) -> Result<(), Error> {
let msg = msg.into();
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
let res = crate::with_global_context(
|secp: &Secp256k1<crate::AllPreallocated>| {
Expand All @@ -389,7 +387,7 @@ pub fn verify(sig: &Signature, msg: impl Into<Message>, pk: &PublicKey) -> Resul
pk.as_c_ptr(),
)
},
Some(&seed),
None,
);
if res == 0 {
Err(Error::IncorrectSignature)
Expand Down
22 changes: 6 additions & 16 deletions src/key/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -302,8 +302,6 @@ impl PublicKey {
/// Returns an error if the resulting key would be invalid.
#[inline]
pub fn mul_tweak(mut self, other: &Scalar) -> Result<PublicKey, Error> {
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
let res = crate::with_global_context(
|secp: &Secp256k1<crate::AllPreallocated>| {
Expand All @@ -313,7 +311,7 @@ impl PublicKey {
other.as_c_ptr(),
)
},
Some(&seed),
None,
);
if res == 1 {
Ok(self)
Expand Down Expand Up @@ -668,8 +666,6 @@ impl Keypair {
// TODO: Add checked implementation
#[inline]
pub fn add_xonly_tweak(mut self, tweak: &Scalar) -> Result<Keypair, Error> {
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
let err = crate::with_global_context(
|secp: &Secp256k1<crate::AllPreallocated>| {
Expand All @@ -679,7 +675,7 @@ impl Keypair {
tweak.as_c_ptr(),
)
},
Some(&seed),
None,
);
if err != 1 {
return Err(Error::InvalidTweak);
Expand Down Expand Up @@ -993,8 +989,6 @@ impl XOnlyPublicKey {
/// ```
pub fn add_tweak(mut self, tweak: &Scalar) -> Result<(XOnlyPublicKey, Parity), Error> {
let mut pk_parity = 0;
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
let mut pubkey = ffi::PublicKey::new();
let mut err = crate::with_global_context(
Expand All @@ -1006,7 +1000,7 @@ impl XOnlyPublicKey {
tweak.as_c_ptr(),
)
},
Some(&seed),
None,
);
if err != 1 {
return Err(Error::InvalidTweak);
Expand All @@ -1021,7 +1015,7 @@ impl XOnlyPublicKey {
&pubkey,
)
},
Some(&seed),
None,
);
if err == 0 {
return Err(Error::InvalidPublicKey);
Expand Down Expand Up @@ -1067,8 +1061,6 @@ impl XOnlyPublicKey {
tweak: Scalar,
) -> bool {
let tweaked_ser = tweaked_key.serialize();
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
let err = crate::with_global_context(
|secp: &Secp256k1<crate::AllPreallocated>| {
Expand All @@ -1080,7 +1072,7 @@ impl XOnlyPublicKey {
tweak.as_c_ptr(),
)
},
Some(&seed),
None,
);

err == 1
Expand Down Expand Up @@ -1327,8 +1319,6 @@ impl<'de> serde::Deserialize<'de> for XOnlyPublicKey {
/// # }
/// ```
pub fn sort_pubkeys(pubkeys: &mut [&PublicKey]) {
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
// SAFETY: `PublicKey` has repr(transparent) so we can convert to `ffi::PublicKey`
let pubkeys_ptr = pubkeys.as_mut_c_ptr() as *mut *const ffi::PublicKey;
Expand All @@ -1337,7 +1327,7 @@ pub fn sort_pubkeys(pubkeys: &mut [&PublicKey]) {
|secp: &Secp256k1<crate::AllPreallocated>| {
ffi::secp256k1_ec_pubkey_sort(secp.ctx.as_ptr(), pubkeys_ptr, pubkeys.len())
},
Some(&seed),
None,
);

if ret == 0 {
Expand Down
31 changes: 7 additions & 24 deletions src/musig.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -411,9 +411,6 @@ impl KeyAggCache {
let mut key_agg_cache = MaybeUninit::<ffi::MusigKeyAggCache>::uninit();
let mut agg_pk = MaybeUninit::<ffi::XOnlyPublicKey>::uninit();

// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];

unsafe {
let pubkeys_ref = core::slice::from_raw_parts(
pubkeys.as_c_ptr() as *const *const ffi::PublicKey,
Expand All @@ -430,7 +427,7 @@ impl KeyAggCache {
pubkeys_ref.len(),
)
},
Some(&seed),
None,
);
if ret == 0 {
// Returns 0 only if the keys are malformed that never happens in safe rust type system.
Expand Down Expand Up @@ -507,8 +504,6 @@ impl KeyAggCache {
/// # }
/// ```
pub fn pubkey_ec_tweak_add(&mut self, tweak: &Scalar) -> Result<PublicKey, InvalidTweakErr> {
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
let mut out = PublicKey::from(ffi::PublicKey::new());

Expand All @@ -521,7 +516,7 @@ impl KeyAggCache {
tweak.as_c_ptr(),
)
},
Some(&seed),
None,
);
if ret == 0 {
Err(InvalidTweakErr)
Expand Down Expand Up @@ -569,8 +564,6 @@ impl KeyAggCache {
/// # }
/// ```
pub fn pubkey_xonly_tweak_add(&mut self, tweak: &Scalar) -> Result<PublicKey, InvalidTweakErr> {
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
let mut out = PublicKey::from(ffi::PublicKey::new());

Expand All @@ -583,7 +576,7 @@ impl KeyAggCache {
tweak.as_c_ptr(),
)
},
Some(&seed),
None,
);
if ret == 0 {
Err(InvalidTweakErr)
Expand Down Expand Up @@ -956,9 +949,6 @@ impl AggregatedNonce {

let mut aggnonce = MaybeUninit::<ffi::MusigAggNonce>::uninit();

// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];

unsafe {
let pubnonces = core::slice::from_raw_parts(
nonces.as_c_ptr() as *const *const ffi::MusigPubNonce,
Expand All @@ -974,7 +964,7 @@ impl AggregatedNonce {
pubnonces.len(),
)
},
Some(&seed),
None,
);
if ret == 0 {
// This can only crash if the individual nonces are invalid which is not possible is rust.
Expand Down Expand Up @@ -1124,9 +1114,6 @@ impl Session {
pub fn new(key_agg_cache: &KeyAggCache, agg_nonce: AggregatedNonce, msg: &[u8; 32]) -> Self {
let mut session = MaybeUninit::<ffi::MusigSession>::uninit();

// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];

unsafe {
let ret = crate::with_global_context(
|secp: &Secp256k1<crate::AllPreallocated>| {
Expand All @@ -1138,7 +1125,7 @@ impl Session {
key_agg_cache.as_ptr(),
)
},
Some(&seed),
None,
);
if ret == 0 {
// Only fails on cryptographically unreachable codes or if the args are invalid.
Expand Down Expand Up @@ -1179,8 +1166,6 @@ impl Session {
keypair: &Keypair,
key_agg_cache: &KeyAggCache,
) -> PartialSignature {
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
let mut partial_sig = MaybeUninit::<ffi::MusigPartialSignature>::uninit();

Expand All @@ -1195,7 +1180,7 @@ impl Session {
self.as_ptr(),
)
},
Some(&seed),
Some(&keypair.secret_bytes()),
);

assert_eq!(res, 1);
Expand Down Expand Up @@ -1283,8 +1268,6 @@ impl Session {
pub_nonce: &PublicNonce,
pub_key: PublicKey,
) -> bool {
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
let ret = crate::with_global_context(
|secp: &Secp256k1<crate::AllPreallocated>| {
Expand All @@ -1297,7 +1280,7 @@ impl Session {
self.as_ptr(),
)
},
Some(&seed),
None,
);
ret == 1
}
Expand Down
4 changes: 1 addition & 3 deletions src/schnorr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -161,8 +161,6 @@ pub fn sign_with_rng<R: Rng + CryptoRng>(msg: &[u8], keypair: &Keypair, rng: &mu

/// Verifies a schnorr signature.
pub fn verify(sig: &Signature, msg: &[u8], pubkey: &XOnlyPublicKey) -> Result<(), Error> {
// We have no seed here but we want rerandomiziation to happen for `rand` users.
let seed = [0_u8; 32];
unsafe {
let ret = crate::with_global_context(
|secp: &Secp256k1<crate::AllPreallocated>| {
Expand All @@ -174,7 +172,7 @@ pub fn verify(sig: &Signature, msg: &[u8], pubkey: &XOnlyPublicKey) -> Result<()
pubkey.as_c_ptr(),
)
},
Some(&seed),
None,
);

if ret == 1 {
Expand Down
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