fix function name and ciphersuite refresh modules (#922)

* fix function name and ciphersuite refresh modules

* core: add min_signers to PublicKeyPackage (#912)

* core: add min_signers to PublicKeyPackage
* fix JSON deserialization when min_signers is missing

* fix warnings, restore wrongly commented out line

Author: conradoplg

frost-core/CHANGELOG.md

@@ -2,7 +2,7 @@
 
 Entries are listed in reverse chronological order.
 
-## Unreleases
+## Unreleased
 
 ### Breaking Changes
 
@@ -12,6 +12,13 @@ Entries are listed in reverse chronological order.
   the default behaviour is now as if `cheater-detection` was enabled. If you
   explicitly *did not enable* it, you can avoid cheater detection by calling
   `aggregate_custom()` with `CheaterDetection::Disabled`.
+* The `std` and `nightly` features were removed from all crates
+* Renamed `frost_core::keys::refresh::refresh_dkg_part_1` to `refresh_dkg_part1`.
+* Fixed the crate-specific versions of the `refresh` module to be non-generic.
+
+### Additional changes
+
+* Added DKG refresh functions to the crate-specific `refresh` modules.
 
 ## 2.2.0
 

frost-core/src/keys.rs

@@ -381,6 +381,11 @@ where
     pub(crate) fn coefficients(&self) -> &[CoefficientCommitment<C>] {
         &self.0
     }
+
+    /// Return the threshold associated with this commitment.
+    pub(crate) fn min_signers(&self) -> u16 {
+        self.0.len() as u16
+    }
 }
 
 /// A secret share generated by performing a (t-out-of-n) secret sharing scheme,
@@ -563,6 +568,7 @@ pub fn split<C: Ciphersuite, R: RngCore + CryptoRng>(
         header: Header::default(),
         verifying_shares,
         verifying_key,
+        min_signers: Some(min_signers),
     };
 
     // Apply post-processing
@@ -706,7 +712,7 @@ where
             signing_share: secret_share.signing_share,
             verifying_share,
             verifying_key,
-            min_signers: secret_share.commitment.0.len() as u16,
+            min_signers: secret_share.commitment.min_signers(),
         })
     }
 }
@@ -716,7 +722,7 @@ where
 ///
 /// Used for verification purposes before publishing a signature.
 #[derive(Clone, Debug, PartialEq, Eq, Getters)]
-#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize))]
 #[cfg_attr(feature = "serde", serde(bound = "C: Ciphersuite"))]
 #[cfg_attr(feature = "serde", serde(deny_unknown_fields))]
 pub struct PublicKeyPackage<C: Ciphersuite> {
@@ -728,6 +734,12 @@ pub struct PublicKeyPackage<C: Ciphersuite> {
     pub(crate) verifying_shares: BTreeMap<Identifier<C>, VerifyingShare<C>>,
     /// The joint public key for the entire group.
     pub(crate) verifying_key: VerifyingKey<C>,
+    /// The minimum number of signers (threshold) required for the group.
+    /// This can be None in packages created with `frost_core` prior to 3.0.0.
+    #[cfg_attr(feature = "serde", serde(skip_serializing_if = "Option::is_none"))]
+    #[cfg_attr(feature = "serde", serde(default))]
+    #[getter(copy)]
+    pub(crate) min_signers: Option<u16>,
 }
 
 impl<C> PublicKeyPackage<C>
@@ -738,11 +750,26 @@ where
     pub fn new(
         verifying_shares: BTreeMap<Identifier<C>, VerifyingShare<C>>,
         verifying_key: VerifyingKey<C>,
+        min_signers: u16,
+    ) -> Self {
+        Self::new_internal(verifying_shares, verifying_key, Some(min_signers))
+    }
+
+    /// Create a new [`PublicKeyPackage`] instance, allowing not specifying the
+    /// number of signers. This is used internally, in particular for testing
+    /// old [`PublicKeyPackage`]s that do not encode the `min_signers`.
+    #[cfg_attr(feature = "internals", visibility::make(pub))]
+    #[cfg_attr(docsrs, doc(cfg(feature = "internals")))]
+    pub(crate) fn new_internal(
+        verifying_shares: BTreeMap<Identifier<C>, VerifyingShare<C>>,
+        verifying_key: VerifyingKey<C>,
+        min_signers: Option<u16>,
     ) -> Self {
         Self {
             header: Header::default(),
             verifying_shares,
             verifying_key,
+            min_signers,
         }
     }
 
@@ -761,6 +788,7 @@ where
         Ok(PublicKeyPackage::new(
             verifying_keys,
             VerifyingKey::from_commitment(commitment)?,
+            commitment.min_signers(),
         ))
     }
 
@@ -777,6 +805,11 @@ where
         let group_commitment = sum_commitments(&commitments)?;
         Self::from_commitment(&identifiers, &group_commitment)
     }
+
+    /// Return the maximum number of signers.
+    pub fn max_signers(&self) -> u16 {
+        self.verifying_shares.len() as u16
+    }
 }
 
 #[cfg(feature = "serialization")]

frost-core/src/keys/dkg.rs

@@ -491,7 +491,7 @@ pub fn part2<C: Ciphersuite>(
     }
 
     for package in round1_packages.values() {
-        if package.commitment.0.len() != secret_package.min_signers as usize {
+        if package.commitment.min_signers() != secret_package.min_signers {
             return Err(Error::IncorrectNumberOfCommitments);
         }
     }

frost-core/src/keys/refresh.rs

@@ -18,7 +18,7 @@
 //!
 //! For the DKG approach, the flow is very similar to [DKG
 //! itself](`https://frost.zfnd.org/tutorial/dkg.html`). Each participant calls
-//! [`refresh_dkg_part_1()`], keeps the returned secret package and sends the
+//! [`refresh_dkg_part1()`], keeps the returned secret package and sends the
 //! returned package to other participants. Then each participants calls
 //! [`refresh_dkg_part2()`] and sends the returned packages to the other
 //! participants. Finally each participant calls [`refresh_dkg_shares()`].
@@ -61,6 +61,14 @@ pub fn compute_refreshing_shares<C: Ciphersuite, R: RngCore + CryptoRng>(
     identifiers: &[Identifier<C>],
     rng: &mut R,
 ) -> Result<(Vec<SecretShare<C>>, PublicKeyPackage<C>), Error<C>> {
+    // Validate min_signers. It's OK if the min_signers is missing, because
+    // we validate it again in `refresh_share()`.
+    if let Some(package_min_signers) = pub_key_package.min_signers {
+        if min_signers != package_min_signers {
+            return Err(Error::InvalidMinSigners);
+        }
+    }
+
     // Validate inputs
     if identifiers.len() != max_signers as usize {
         return Err(Error::IncorrectNumberOfIdentifiers);
@@ -110,6 +118,7 @@ pub fn compute_refreshing_shares<C: Ciphersuite, R: RngCore + CryptoRng>(
         header: pub_key_package.header,
         verifying_shares: refreshed_verifying_shares,
         verifying_key: pub_key_package.verifying_key,
+        min_signers: Some(pub_key_package.min_signers.unwrap_or(min_signers)),
     };
 
     Ok((refreshing_shares_minus_identity, refreshed_pub_key_package))
@@ -168,7 +177,7 @@ pub fn refresh_share<C: Ciphersuite>(
 /// It returns the [`round1::SecretPackage`] that must be kept in memory
 /// by the participant for the other steps, and the [`round1::Package`] that
 /// must be sent to each other participant in the refresh run.
-pub fn refresh_dkg_part_1<C: Ciphersuite, R: RngCore + CryptoRng>(
+pub fn refresh_dkg_part1<C: Ciphersuite, R: RngCore + CryptoRng>(
     identifier: Identifier<C>,
     max_signers: u16,
     min_signers: u16,
@@ -460,6 +469,7 @@ pub fn refresh_dkg_shares<C: Ciphersuite>(
         header: old_pub_key_package.header,
         verifying_shares: new_verifying_shares,
         verifying_key: old_pub_key_package.verifying_key,
+        min_signers: Some(round2_secret_package.min_signers),
     };
 
     let key_package = KeyPackage {

frost-core/src/lib.rs

@@ -758,7 +758,15 @@ pub fn verify_signature_share<C: Ciphersuite>(
     // In order to reuse `pre_aggregate()`, we need to create some "dummy" containers
     let signature_shares = BTreeMap::from([(identifier, *signature_share)]);
     let verifying_shares = BTreeMap::from([(identifier, *verifying_share)]);
-    let public_key_package = PublicKeyPackage::new(verifying_shares, *verifying_key);
+    let public_key_package = PublicKeyPackage {
+        verifying_shares,
+        verifying_key: *verifying_key,
+        // Use None since we don't have the min_signers value here. This
+        // can only cause problems if the `pre_aggregate` function relies on it.
+        // This has been documented in `pre_aggregate()`.
+        min_signers: None,
+        header: Header::default(),
+    };
 
     let (signing_package, signature_shares, pubkeys) =
         <C>::pre_aggregate(signing_package, &signature_shares, &public_key_package)?;