Merge pull request #485 from Concordium/impl-fromstr-display-prf-key

Add FromStr and Display impls for PRF keys

rust-src/concordium_base/CHANGELOG.md

@@ -4,6 +4,8 @@
 - Support `P7` protocol version.
 - The `Debug` implementation for `ContractEvent` displays the value in `hex`.
   The alternate formatter (using `#`) displays it as a list of bytes.
+- Add `FromStr` and `Display` instances to `dodis_yampolskiy_prf::SecretKey`.
+- Change `Debug` instance of `dodis_yampolskiy_prf::SecretKey` to hide the value.
 
 ## 3.2.0 (2023-11-22)
 

rust-src/concordium_base/src/dodis_yampolskiy_prf/secret.rs

@@ -10,7 +10,7 @@ use rand::*;
 use std::rc::Rc;
 
 /// A PRF key.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, SerdeBase16Serialize)]
+#[derive(Clone, PartialEq, Eq, Serialize, SerdeBase16Serialize)]
 pub struct SecretKey<C: Curve>(Rc<Secret<C::Scalar>>);
 
 /// This trait allows automatic conversion of `&SecretKey<C>` to `&C::Scalar`.
@@ -74,6 +74,36 @@ impl<C: Curve> SecretKey<C> {
     }
 }
 
+impl<C: Curve> std::fmt::Display for SecretKey<C> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(f, "<Dodis Yampolskiy SecretKey>")
+    }
+}
+
+impl<C: Curve> std::fmt::Debug for SecretKey<C> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(f, "<Dodis Yampolskiy SecretKey>")
+    }
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum SecretKeyFromStrError {
+    #[error("Invalid secret key: {0}")]
+    InvalidKey(#[from] anyhow::Error),
+    #[error("Invalid hex string: {0}")]
+    InvalidHex(#[from] hex::FromHexError),
+}
+
+impl<C: Curve> std::str::FromStr for SecretKey<C> {
+    type Err = SecretKeyFromStrError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut bytes = std::io::Cursor::new(hex::decode(s)?);
+        let key = from_bytes(&mut bytes)?;
+        Ok(key)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;