From 6a26e82b607455ef8ea4369cbfd93b4500c1df04 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20N=C3=BA=C3=B1ez?= <david@nucypher.com>
Date: Thu, 14 Mar 2024 17:36:43 +0100
Subject: [PATCH] Some tests fixed: share updating should be done on top of
 blinded shares

As suspected 2 commits ago
---
 ferveo-tdec/src/key_share.rs | 10 ++++++++++
 ferveo-tdec/src/lib.rs       | 10 ++++++----
 ferveo/src/refresh.rs        | 28 +++++++++++++++++++++++-----
 3 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/ferveo-tdec/src/key_share.rs b/ferveo-tdec/src/key_share.rs
index 46536aa0..66431ca4 100644
--- a/ferveo-tdec/src/key_share.rs
+++ b/ferveo-tdec/src/key_share.rs
@@ -18,6 +18,8 @@ pub struct ShareCommitment<E: Pairing>(
     #[serde_as(as = "serialization::SerdeAs")] pub E::G1Affine, // A_{i, \omega_i}
 );
 
+// TODO: Improve by adding share commitment here
+// TODO: Is this a test utility perhaps?
 #[derive(Debug, Copy, Clone)]
 pub struct BlindedKeyShare<E: Pairing> {
     pub validator_public_key: E::G2Affine, // [b] H
@@ -52,6 +54,14 @@ impl<E: Pairing> BlindedKeyShare<E> {
     //     self.blinded_key_share =
     //         self.blinded_key_share.mul(-*omega_inv).into_affine();
     // }
+    pub fn unblind(
+        &self,
+        unblinding_factor: E::ScalarField,
+    ) -> PrivateKeyShare<E> {
+        PrivateKeyShare::<E>(
+            self.blinded_key_share.mul(unblinding_factor).into_affine(),
+        )
+    }
 }
 
 #[serde_as]
diff --git a/ferveo-tdec/src/lib.rs b/ferveo-tdec/src/lib.rs
index 78a32d2b..8ba22849 100644
--- a/ferveo-tdec/src/lib.rs
+++ b/ferveo-tdec/src/lib.rs
@@ -242,13 +242,15 @@ pub mod test_common {
         .enumerate()
         {
             let private_key_share = PrivateKeyShare::<E>(*private_share);
-            let b = E::ScalarField::one();  // FIXME: rand(rng);
-            let blinded_key_share: BlindedKeyShare<E> = private_key_share.blind(b);
+            let blinding_factor = E::ScalarField::rand(rng);
+            let blinded_key_share: BlindedKeyShare<E> =
+                private_key_share.blind(blinding_factor);
+
             private_contexts.push(PrivateDecryptionContextSimple::<E> {
                 index,
                 setup_params: SetupParams {
-                    b,
-                    b_inv: b.inverse().unwrap(),
+                    b: blinding_factor,
+                    b_inv: blinding_factor.inverse().unwrap(),
                     g,
                     h_inv: E::G2Prepared::from(-h.into_group()),
                     g_inv: E::G1Prepared::from(-g.into_group()),
diff --git a/ferveo/src/refresh.rs b/ferveo/src/refresh.rs
index d4b5aa93..6931ec58 100644
--- a/ferveo/src/refresh.rs
+++ b/ferveo/src/refresh.rs
@@ -46,7 +46,7 @@ impl<E: Pairing> PrivateKeyShare<E> {
         &self,
         share_updates: &[ShareUpdate<E>],
     ) -> UpdatedPrivateKeyShare<E> {
-        // TODO: Validate commitments from share update
+        // TODO: Validate commitments from share update  // FIXME: Don't forget!!!!!
         let updated_key_share = share_updates
             .iter()
             .fold(self.0 .0, |acc, delta| (acc + delta.update).into());
@@ -316,7 +316,8 @@ mod tests_refresh {
     use ark_bls12_381::Fr;
     use ark_std::{test_rng, UniformRand, Zero};
     use ferveo_tdec::{
-        test_common::setup_simple, PrivateDecryptionContextSimple,
+        test_common::setup_simple, BlindedKeyShare,
+        PrivateDecryptionContextSimple,
     };
     use rand_core::RngCore;
     use test_case::{test_case, test_matrix};
@@ -601,9 +602,26 @@ mod tests_refresh {
                     .collect();
 
                 // And creates a new, refreshed share
-                let updated_share =
-                    PrivateKeyShare(p.private_key_share.clone())
-                        .create_updated_key_share(&updates_for_participant);
+                let blinded_key_share =
+                    p.public_decryption_contexts[p.index].blinded_key_share;
+
+                // TODO: Encapsulate this somewhere, originally from PrivateKeyShare.create_updated_key_share
+                // FIXME: Validate commitments from share update, don't forget!!!!!
+                let updated_blinded_key_share: BlindedKeyShare<E> =
+                    BlindedKeyShare {
+                        validator_public_key: blinded_key_share
+                            .validator_public_key,
+                        blinded_key_share: updates_for_participant.iter().fold(
+                            blinded_key_share.blinded_key_share,
+                            |acc, delta| (acc + delta.update).into(),
+                        ),
+                    };
+
+                let unblinding_factor = p.setup_params.b_inv;
+                let updated_share = UpdatedPrivateKeyShare(
+                    updated_blinded_key_share.unblind(unblinding_factor),
+                );
+
                 (p.index as u32, updated_share)
             })
             // We only need `threshold` refreshed shares to recover the original share