core: Add owns and owns_unchecked to SecretKey (#216)

core/CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add a light sync method in the `ViewKey` [#199]
 - Add function `value_commitment` [#201]
 - Add function `transparent_value_commitment` [#201]
+- Add `owns()` and `owns_unchecked()` to `Secretkey` [#146]
 
 ### Changed
 
@@ -345,6 +346,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Canonical implementation shielded by feature.
 
 <!-- ISSUES -->
+[#146]: https://github.com/dusk-network/phoenix/issues/146
 [#208]: https://github.com/dusk-network/phoenix/issues/208
 [#201]: https://github.com/dusk-network/phoenix/issues/201
 [#199]: https://github.com/dusk-network/phoenix/issues/199

core/src/keys/secret.rs

@@ -4,9 +4,9 @@
 //
 // Copyright (c) DUSK NETWORK. All rights reserved.
 
-use crate::{keys::hash, StealthAddress};
+use crate::{keys::hash, Note, StealthAddress};
 
-use dusk_jubjub::JubJubScalar;
+use dusk_jubjub::{JubJubScalar, GENERATOR_EXTENDED};
 use ff::Field;
 use jubjub_schnorr::SecretKey as NoteSecretKey;
 use zeroize::Zeroize;
@@ -86,6 +86,27 @@ impl SecretKey {
 
         NoteSecretKey::from(hash(&aR) + self.b)
     }
+
+    /// Checks if `note_pk ?= (H(R · a) + b) · G`
+    pub fn owns(&self, note: &Note) -> bool {
+        let sa = note.stealth_address();
+
+        let aR = sa.R() * self.a();
+        let hash_aR = hash(&aR);
+        let note_sk = hash_aR + self.b();
+
+        let note_pk = GENERATOR_EXTENDED * note_sk;
+
+        sa.note_pk().as_ref() == &note_pk
+    }
+
+    /// Checks if `k_sync ?= R_sync · a`
+    pub fn owns_unchecked(&self, note: &Note) -> bool {
+        let sa = note.sync_address();
+        let aR = sa.R() * self.a();
+
+        sa.k() == &aR
+    }
 }
 
 impl ConstantTimeEq for SecretKey {

core/src/keys/view.rs

@@ -67,9 +67,9 @@ impl ViewKey {
         let sa = note.stealth_address();
 
         let aR = sa.R() * self.a();
-        let aR = hash(&aR);
-        let aR = GENERATOR_EXTENDED * aR;
-        let note_pk = aR + self.B();
+        let hash_aR = hash(&aR);
+        let hash_aR_G = GENERATOR_EXTENDED * hash_aR;
+        let note_pk = hash_aR_G + self.B();
 
         sa.note_pk().as_ref() == &note_pk
     }

core/tests/keys.rs

@@ -70,6 +70,8 @@ fn keys_consistency() {
 
     assert!(vk.owns(&note));
     assert!(vk.owns_unchecked(&note));
+    assert!(sk.owns(&note));
+    assert!(sk.owns_unchecked(&note));
 
     let wrong_sk = SecretKey::random(&mut rng);
     let wrong_vk = ViewKey::from(&wrong_sk);
@@ -79,6 +81,8 @@ fn keys_consistency() {
 
     assert!(!wrong_vk.owns(&note));
     assert!(!wrong_vk.owns_unchecked(&note));
+    assert!(!wrong_sk.owns(&note));
+    assert!(!wrong_sk.owns_unchecked(&note));
 
     let sa = pk.gen_stealth_address(&r);