Merge branch 'tiago/zeroize-secret-keys' (#1956)

.changelog/unreleased/miscellaneous/1958-zeroize-secret-keys.md

@@ -0,0 +1,2 @@
+- Tag `ed25519` keys with `ZeroizeOnDrop`
+  ([\#1958](https://github.com/anoma/namada/pull/1958))

core/src/types/key/ed25519.rs

@@ -10,7 +10,7 @@ use data_encoding::HEXLOWER;
 #[cfg(feature = "rand")]
 use rand::{CryptoRng, RngCore};
 use serde::{Deserialize, Serialize};
-use zeroize::Zeroize;
+use zeroize::{Zeroize, ZeroizeOnDrop};
 
 use super::{
     ParsePublicKeyError, ParseSecretKeyError, ParseSignatureError, RefTo,
@@ -125,7 +125,7 @@ impl FromStr for PublicKey {
 }
 
 /// Ed25519 secret key
-#[derive(Debug, Serialize, Deserialize, Zeroize)]
+#[derive(Debug, Serialize, Deserialize, Zeroize, ZeroizeOnDrop)]
 pub struct SecretKey(pub Box<ed25519_consensus::SigningKey>);
 
 impl super::SecretKey for SecretKey {
@@ -223,12 +223,6 @@ impl FromStr for SecretKey {
     }
 }
 
-impl Drop for SecretKey {
-    fn drop(&mut self) {
-        self.0.zeroize();
-    }
-}
-
 /// Ed25519 signature
 #[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
 pub struct Signature(pub ed25519_consensus::Signature);