From 5461eb0dad80fe30dab9ea820c3ac9491936a2a6 Mon Sep 17 00:00:00 2001
From: thesimplekid <tsk@thesimplekid.com>
Date: Wed, 27 Mar 2024 20:18:08 +0000
Subject: [PATCH] feat(NUT12): BlindedSignature and Proof DLEQ

---
 crates/cashu/src/dhke.rs       |  5 ++---
 crates/cashu/src/nuts/mod.rs   |  2 +-
 crates/cashu/src/nuts/nut00.rs |  8 ++++----
 crates/cashu/src/nuts/nut12.rs | 37 ++++++++++++++++++++++++----------
 4 files changed, 33 insertions(+), 19 deletions(-)

diff --git a/crates/cashu/src/dhke.rs b/crates/cashu/src/dhke.rs
index 5e7159ba..a1512e74 100644
--- a/crates/cashu/src/dhke.rs
+++ b/crates/cashu/src/dhke.rs
@@ -134,10 +134,10 @@ mod wallet {
             #[cfg(feature = "nut12")]
             {
                 let dleq = if let Some(dleq) = blinded_signature.dleq {
-                    Some(DleqProof {
+                    Some(ProofDleq {
                         e: dleq.e,
                         s: dleq.s,
-                        r: Some(r),
+                        r,
                     })
                 } else {
                     None
@@ -391,7 +391,6 @@ mod tests {
             let sec = SecretKey::new(ScalarPrimitive::ONE);
 
             let (blinded_message, _r) = blind_message(message.as_bytes(), Some(sec)).unwrap();
-
             // A
             let bob_sec = SecretKey::new(ScalarPrimitive::ONE);
 
diff --git a/crates/cashu/src/nuts/mod.rs b/crates/cashu/src/nuts/mod.rs
index 6a23a458..23b1a50d 100644
--- a/crates/cashu/src/nuts/mod.rs
+++ b/crates/cashu/src/nuts/mod.rs
@@ -48,6 +48,6 @@ pub use nut10::{Kind, Secret as Nut10Secret, SecretData};
 #[cfg(feature = "nut11")]
 pub use nut11::{P2PKConditions, SigFlag, Signatures, SigningKey, VerifyingKey};
 #[cfg(feature = "nut12")]
-pub use nut12::DleqProof;
+pub use nut12::{BlindedSignatureDleq, ProofDleq};
 
 pub type Proofs = Vec<Proof>;
diff --git a/crates/cashu/src/nuts/nut00.rs b/crates/cashu/src/nuts/nut00.rs
index 8ecc17ed..a8b54892 100644
--- a/crates/cashu/src/nuts/nut00.rs
+++ b/crates/cashu/src/nuts/nut00.rs
@@ -8,7 +8,7 @@ use std::str::FromStr;
 use serde::{Deserialize, Serialize};
 
 #[cfg(feature = "nut12")]
-use super::DleqProof;
+use super::{BlindedSignatureDleq, ProofDleq};
 use super::{Id, Proofs, PublicKey};
 use crate::error::Error;
 #[cfg(feature = "nut11")]
@@ -27,7 +27,7 @@ pub struct BlindedMessage {
     /// Keyset Id
     #[serde(rename = "id")]
     pub keyset_id: Id,
-    /// encrypted secret message (B_)
+    /// Blinded secret message (B_)
     #[serde(rename = "B_")]
     pub b: PublicKey,
     /// Witness
@@ -424,7 +424,7 @@ pub struct BlindedSignature {
     pub c: PublicKey,
     /// DLEQ Proof
     #[cfg(feature = "nut12")]
-    pub dleq: Option<DleqProof>,
+    pub dleq: Option<BlindedSignatureDleq>,
 }
 
 /// Proofs [NUT-00]
@@ -450,7 +450,7 @@ pub struct Proof {
     pub witness: Option<Signatures>,
     /// DLEQ Proof
     #[cfg(feature = "nut12")]
-    pub dleq: Option<DleqProof>,
+    pub dleq: Option<ProofDleq>,
 }
 
 impl Proof {
diff --git a/crates/cashu/src/nuts/nut12.rs b/crates/cashu/src/nuts/nut12.rs
index 437ef745..7e5d8d2d 100644
--- a/crates/cashu/src/nuts/nut12.rs
+++ b/crates/cashu/src/nuts/nut12.rs
@@ -26,11 +26,16 @@ pub enum Error {
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
-pub struct DleqProof {
+pub struct BlindedSignatureDleq {
     pub e: SecretKey,
     pub s: SecretKey,
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub r: Option<SecretKey>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct ProofDleq {
+    pub e: SecretKey,
+    pub s: SecretKey,
+    pub r: SecretKey,
 }
 
 fn verify_dleq(
@@ -74,7 +79,7 @@ fn calculate_dleq(
     blinded_signature: k256::PublicKey,
     blinded_message: &k256::PublicKey,
     mint_secretkey: &k256::SecretKey,
-) -> Result<DleqProof, Error> {
+) -> Result<BlindedSignatureDleq, Error> {
     // Random nonce
     let r: k256::SecretKey = SecretKey::random().into();
 
@@ -95,10 +100,9 @@ fn calculate_dleq(
 
     let s: k256::SecretKey = k256::SecretKey::new(s.into());
 
-    Ok(DleqProof {
+    Ok(BlindedSignatureDleq {
         e: e_sk.into(),
         s: s.into(),
-        r: None,
     })
 }
 
@@ -106,11 +110,7 @@ impl Proof {
     pub fn verify_dleq(&self, mint_pubkey: &PublicKey) -> Result<(), Error> {
         let (e, s, blinding_factor): (k256::SecretKey, k256::SecretKey, k256::SecretKey) =
             if let Some(dleq) = self.dleq.clone() {
-                if let Some(r) = dleq.r {
-                    (dleq.e.into(), dleq.s.into(), r.into())
-                } else {
-                    return Err(Error::IncompleteDleqProof);
-                }
+                (dleq.e.into(), dleq.s.into(), dleq.r.into())
             } else {
                 return Err(Error::MissingDleqProof);
             };
@@ -224,4 +224,19 @@ mod tests {
 
         blinded.verify_dleq(&mint_key, &blinded_secret).unwrap()
     }
+
+    #[test]
+    fn test_proof_dleq() {
+        let proof = r#"{"amount": 1,"id": "00882760bfa2eb41","secret": "daf4dd00a2b68a0858a80450f52c8a7d2ccf87d375e43e216e0c571f089f63e9","C": "024369d2d22a80ecf78f3937da9d5f30c1b9f74f0c32684d583cca0fa6a61cdcfc","dleq": {"e": "b31e58ac6527f34975ffab13e70a48b6d2b0d35abc4b03f0151f09ee1a9763d4","s": "8fbae004c59e754d71df67e392b6ae4e29293113ddc2ec86592a0431d16306d8","r": "a6d13fcd7a18442e6076f5e1e7c887ad5de40a019824bdfa9fe740d302e8d861"}}"#;
+
+        let proof: Proof = serde_json::from_str(proof).unwrap();
+
+        // A
+        let a: PublicKey = PublicKey::from_str(
+            "0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798",
+        )
+        .unwrap();
+
+        assert!(proof.verify_dleq(&a).is_ok());
+    }
 }