From 529035e4629fdf1de64d74a5b53aa5e0778b0a69 Mon Sep 17 00:00:00 2001
From: xevisalle <38231508+xevisalle@users.noreply.github.com>
Date: Fri, 5 Apr 2024 14:49:56 +0200
Subject: [PATCH] Use Blake for stealth addresses (#147)

---
 CHANGELOG.md       |  1 +
 src/keys.rs        |  8 ++++++++
 src/keys/public.rs |  4 ++--
 src/keys/secret.rs |  4 ++--
 src/keys/view.rs   |  4 ++--
 src/lib.rs         |  4 ++--
 src/permutation.rs | 14 --------------
 7 files changed, 17 insertions(+), 22 deletions(-)
 delete mode 100644 src/permutation.rs

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 13aa39b..6b7c1f9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Update bls12_381-bls -> 0.2
 - Update jubjub-schnorr -> 0.2
+- Use Blake for computing the stealth addresses, instead of Poseidon.
 
 ## [0.25.0] - 2024-01-24
 
diff --git a/src/keys.rs b/src/keys.rs
index 6be28d8..45c318c 100644
--- a/src/keys.rs
+++ b/src/keys.rs
@@ -4,7 +4,15 @@
 //
 // Copyright (c) DUSK NETWORK. All rights reserved.
 
+use dusk_jubjub::{JubJubAffine, JubJubExtended, JubJubScalar};
+
 pub mod public;
 pub mod secret;
 pub mod stealth;
 pub mod view;
+
+/// Hashes a JubJub's ExtendedPoint into a JubJub's Scalar using the JubJub's
+/// hash to scalar function
+pub fn hash(p: &JubJubExtended) -> JubJubScalar {
+    JubJubScalar::hash_to_scalar(&JubJubAffine::from(p).to_bytes())
+}
diff --git a/src/keys/public.rs b/src/keys/public.rs
index 6b709f4..3f51d7d 100644
--- a/src/keys/public.rs
+++ b/src/keys/public.rs
@@ -4,7 +4,7 @@
 //
 // Copyright (c) DUSK NETWORK. All rights reserved.
 
-use crate::{permutation, SecretKey, StealthAddress, ViewKey};
+use crate::{keys::hash, SecretKey, StealthAddress, ViewKey};
 
 use dusk_jubjub::{JubJubAffine, JubJubExtended, JubJubScalar};
 
@@ -50,7 +50,7 @@ impl PublicKey {
         let R = G * r;
 
         let rA = self.A * r;
-        let rA = permutation::hash(&rA);
+        let rA = hash(&rA);
         let rA = G * rA;
 
         let pk_r = rA + self.B;
diff --git a/src/keys/secret.rs b/src/keys/secret.rs
index 1c367e9..0677b1a 100644
--- a/src/keys/secret.rs
+++ b/src/keys/secret.rs
@@ -4,7 +4,7 @@
 //
 // Copyright (c) DUSK NETWORK. All rights reserved.
 
-use crate::{permutation, StealthAddress};
+use crate::{keys::hash, StealthAddress};
 use dusk_jubjub::JubJubScalar;
 use ff::Field;
 use jubjub_schnorr::SecretKey as NoteSecretKey;
@@ -58,7 +58,7 @@ impl SecretKey {
     /// With the formula: `sk_r = H(a · R) + b`
     pub fn sk_r(&self, sa: &StealthAddress) -> NoteSecretKey {
         let aR = sa.R() * self.a;
-        let aR = permutation::hash(&aR);
+        let aR = hash(&aR);
 
         (aR + self.b).into()
     }
diff --git a/src/keys/view.rs b/src/keys/view.rs
index d1b8e55..a3d4a5a 100644
--- a/src/keys/view.rs
+++ b/src/keys/view.rs
@@ -6,7 +6,7 @@
 
 use crate::keys::stealth;
 
-use crate::{permutation, SecretKey};
+use crate::{keys::hash, SecretKey};
 
 use dusk_bytes::{DeserializableSlice, Error, Serializable};
 use dusk_jubjub::{
@@ -69,7 +69,7 @@ impl ViewKey {
         let sa = owner.stealth_address();
 
         let aR = sa.R() * self.a();
-        let aR = permutation::hash(&aR);
+        let aR = hash(&aR);
         let aR = GENERATOR_EXTENDED * aR;
         let pk_r = aR + self.B();
 
diff --git a/src/lib.rs b/src/lib.rs
index dd9ed92..8e3fe3d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -29,8 +29,8 @@ pub mod note;
 /// Phoenix Core Keys & Addresses
 mod keys;
 
-mod permutation;
-
+/// Hash function
+pub use keys::hash;
 /// Public (Spend) Key
 pub use keys::public::PublicKey;
 /// Secret (Spend) Key
diff --git a/src/permutation.rs b/src/permutation.rs
deleted file mode 100644
index 1a3edd1..0000000
--- a/src/permutation.rs
+++ /dev/null
@@ -1,14 +0,0 @@
-// This Source Code Form is subject to the terms of the Mozilla Public
-// License, v. 2.0. If a copy of the MPL was not distributed with this
-// file, You can obtain one at http://mozilla.org/MPL/2.0/.
-//
-// Copyright (c) DUSK NETWORK. All rights reserved.
-
-use dusk_jubjub::{JubJubExtended, JubJubScalar};
-use dusk_poseidon::sponge::truncated;
-
-/// Hashes a JubJub's ExtendedPoint into a JubJub's Scalar using the poseidon
-/// hash function
-pub fn hash(p: &JubJubExtended) -> JubJubScalar {
-    truncated::hash(&p.to_hash_inputs())
-}