refactor: secret as hex bytes

crates/cashu/src/dhke.rs

@@ -6,7 +6,7 @@ pub use mint::{sign_message, verify_message};
 #[cfg(feature = "wallet")]
 pub use wallet::{blind_message, construct_proofs, unblind_message};
 
-fn hash_to_curve(message: &[u8]) -> k256::PublicKey {
+pub fn hash_to_curve(message: &[u8]) -> k256::PublicKey {
     let mut msg_to_hash = message.to_vec();
 
     loop {
@@ -130,7 +130,7 @@ mod mint {
         msg: &Secret,
     ) -> Result<(), error::mint::Error> {
         // Y
-        let y = hash_to_curve(msg.as_bytes());
+        let y = hash_to_curve(&msg.to_bytes()?);
 
         if unblinded_message
             == k256::PublicKey::try_from(*y.as_affine() * Scalar::from(a.as_scalar_primitive()))?
@@ -144,6 +144,8 @@ mod mint {
 
 #[cfg(test)]
 mod tests {
+    use core::panic;
+
     use hex::decode;
     use k256::elliptic_curve::scalar::ScalarPrimitive;
 
@@ -349,7 +351,7 @@ mod tests {
             let x = Secret::new();
 
             // Y
-            let y = hash_to_curve(x.as_bytes());
+            let y = hash_to_curve(&x.to_bytes().unwrap());
 
             // B_
             let blinded = blind_message(&y.to_sec1_bytes(), None).unwrap();

crates/cashu/src/error.rs

@@ -69,6 +69,8 @@ pub mod wallet {
         /// Url Parse error
         #[error("Url Parse")]
         UrlParse,
+        #[error("`{0}`")]
+        Secret(#[from] crate::secret::Error),
         /// Custom Error message
         #[error("`{0}`")]
         CustomError(String),
@@ -110,6 +112,8 @@ pub mod mint {
         #[error("Unknown Keyset")]
         UnknownKeySet,
         #[error("`{0}`")]
+        Secret(#[from] crate::secret::Error),
+        #[error("`{0}`")]
         CustomError(String),
     }
 }

crates/cashu/src/nuts/nut00.rs

@@ -165,7 +165,7 @@ pub mod wallet {
 
             for amount in amount_split {
                 let secret = Secret::new();
-                let (blinded, r) = blind_message(secret.as_bytes(), None)?;
+                let (blinded, r) = blind_message(&secret.to_bytes()?, None)?;
 
                 let blinded_message = BlindedMessage {
                     amount,
@@ -192,7 +192,7 @@ pub mod wallet {
             let mut output = Vec::with_capacity(secrets.len());
 
             for (secret, amount) in secrets.into_iter().zip(amounts) {
-                let (blinded, r) = blind_message(secret.as_bytes(), None)?;
+                let (blinded, r) = blind_message(&secret.to_bytes()?, None)?;
 
                 let blinded_message = BlindedMessage {
                     amount,
@@ -219,7 +219,7 @@ pub mod wallet {
 
             for _i in 0..count {
                 let secret = Secret::new();
-                let (blinded, r) = blind_message(secret.as_bytes(), None)?;
+                let (blinded, r) = blind_message(&secret.to_bytes()?, None)?;
 
                 let blinded_message = BlindedMessage {
                     amount: Amount::ZERO,
@@ -255,7 +255,8 @@ pub mod wallet {
                 let secret = Secret::from_seed(mnemonic, keyset_id, counter);
                 let blinding_factor = SecretKey::from_seed(mnemonic, keyset_id, counter);
 
-                let (blinded, r) = blind_message(secret.as_bytes(), Some(blinding_factor.into()))?;
+                let (blinded, r) =
+                    blind_message(&secret.to_bytes()?, Some(blinding_factor.into()))?;
 
                 let blinded_message = BlindedMessage {
                     keyset_id,

crates/cashu/src/secret.rs

@@ -18,6 +18,8 @@ pub struct Secret(String);
 pub enum Error {
     #[error("Invalid secret length: `{0}`")]
     InvalidLength(u64),
+    #[error("Hex error: `{0}`")]
+    Hex(#[from] hex::FromHexError),
 }
 
 impl Default for Secret {
@@ -56,8 +58,8 @@ impl Secret {
         Self(hex::encode(xpriv.private_key().to_bytes()))
     }
 
-    pub fn as_bytes(&self) -> &[u8] {
-        self.0.as_bytes()
+    pub fn to_bytes(&self) -> Result<Vec<u8>, Error> {
+        Ok(hex::decode(&self.0)?)
     }
 }