zeroize remaining secret values (#428)

frost-core/src/frost/keys.rs

@@ -518,17 +518,20 @@ fn evaluate_vss<C: Ciphersuite>(
 /// When using a central dealer, [`SecretShare`]s are distributed to
 /// participants, who then perform verification, before deriving
 /// [`KeyPackage`]s, which they store to later use during signing.
-#[derive(Clone, Debug, PartialEq, Eq, Getters)]
+#[derive(Clone, Debug, PartialEq, Eq, Getters, Zeroize)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 #[cfg_attr(feature = "serde", serde(deny_unknown_fields))]
 pub struct KeyPackage<C: Ciphersuite> {
     /// Denotes the participant identifier each secret share key package is owned by.
+    #[zeroize(skip)]
     pub(crate) identifier: Identifier<C>,
     /// This participant's secret share.
     pub(crate) secret_share: SigningShare<C>,
     /// This participant's public key.
+    #[zeroize(skip)]
     pub(crate) public: VerifyingShare<C>,
     /// The public signing key that represents the entire group.
+    #[zeroize(skip)]
     pub(crate) group_public: VerifyingKey<C>,
     /// Ciphersuite ID for serialization
     #[cfg_attr(

frost-core/src/frost/keys/dkg.rs

@@ -48,6 +48,7 @@ use super::{
 /// DKG Round 1 structures.
 pub mod round1 {
     use derive_getters::Getters;
+    use zeroize::Zeroize;
 
     use super::*;
 
@@ -127,11 +128,23 @@ pub mod round1 {
                 .finish()
         }
     }
+
+    impl<C> Zeroize for SecretPackage<C>
+    where
+        C: Ciphersuite,
+    {
+        fn zeroize(&mut self) {
+            for i in 0..self.coefficients.len() {
+                self.coefficients[i] = <<C::Group as Group>::Field>::zero();
+            }
+        }
+    }
 }
 
 /// DKG Round 2 structures.
 pub mod round2 {
     use derive_getters::Getters;
+    use zeroize::Zeroize;
 
     use super::*;
 
@@ -215,6 +228,15 @@ pub mod round2 {
                 .finish()
         }
     }
+
+    impl<C> Zeroize for SecretPackage<C>
+    where
+        C: Ciphersuite,
+    {
+        fn zeroize(&mut self) {
+            self.secret_share = <<C::Group as Group>::Field>::zero();
+        }
+    }
 }
 
 /// Performs the first part of the distributed key generation protocol