Encrypt invites_remaining during blockage migration

Reverts ed72b05347

crates/lox-library/src/proto/blockage_migration.rs

@@ -104,9 +104,11 @@ pub struct Response {
     // The fields for the new Lox credential
     P: RistrettoPoint,
     EncQ: (RistrettoPoint, RistrettoPoint),
+    EncInvRemain: (RistrettoPoint, RistrettoPoint),
     id_server: Scalar,
     TId: RistrettoPoint,
     TBucket: RistrettoPoint,
+    TInvRemain: RistrettoPoint,
     TBlockages: RistrettoPoint,
 
     // The lox_zkp
@@ -153,10 +155,11 @@ define_proof! {
     blindissue,
     "Blockage Migration Blind Issuing",
     (x0, x0tilde, xid, xbucket, xlevel, xsince, xinvremain, xblockages,
-     s, b, tid, tbucket, tblockages),
+     s, b, tid, tbucket, tinvremain, tblockages),
     (P, EncQ0, EncQ1, X0, Xid, Xbucket, Xlevel, Xsince, Xinvremain,
-    Xblockages, Plevel, Psince, Pinvremain, TId, TBucket, TBlockages,
-     D, EncId0, EncId1, EncBucket0, EncBucket1, EncBlockages0, EncBlockages1),
+    Xblockages, Plevel, Psince, TId, TBucket, TInvRemain, TBlockages,
+     D, EncId0, EncId1, EncBucket0, EncBucket1, EncInvRemain0,
+     EncInvRemain1, EncBlockages0, EncBlockages1),
     (A, B):
     Xid = (xid*A),
     Xlevel = (xlevel*A),
@@ -170,11 +173,15 @@ define_proof! {
     TId = (tid*A),
     TBucket = (b*Xbucket),
     TBucket = (tbucket*A),
+    TInvRemain = (b*Xinvremain),
+    TInvRemain = (tinvremain*A),
     TBlockages = (b*Xblockages),
     TBlockages = (tblockages*A),
     EncQ0 = (s*B + tid*EncId0 + tbucket*EncBucket0
+        + tinvremain*EncInvRemain0
         + tblockages*EncBlockages0),
     EncQ1 = (s*D + tid*EncId1 + tbucket*EncBucket1
+        + tinvremain*EncInvRemain1
          + tblockages*EncBlockages1
         + x0*P + xlevel*Plevel + xsince*Psince)
 }
@@ -487,6 +494,12 @@ impl BridgeAuth {
         // invitations for moving from level i to level i+1)
         let invremain: Scalar = LEVEL_INVITATIONS[(level - 3) as usize].into();
 
+        let sinvremain = Scalar::random(&mut rng);
+        let EncInvRemain = (
+            &sinvremain * Btable,
+            &invremain * Btable + sinvremain * req.D,
+        );
+
         // Compute the MAC on the visible attributes
         let b = Scalar::random(&mut rng);
         let P = &b * Btable;
@@ -507,6 +520,9 @@ impl BridgeAuth {
         let tbucket = self.lox_priv.x[2] * b;
         let TBucket = &tbucket * Atable;
         let EncQBucket = (tbucket * req.EncBucket.0, tbucket * req.EncBucket.1);
+        let tinvremain = self.lox_priv.x[5] * b;
+        let TInvRemain = &tinvremain * Atable;
+        let EncQInvRemain = (tinvremain * EncInvRemain.0, tinvremain * EncInvRemain.1);
         let tblockages = self.lox_priv.x[6] * b;
         let TBlockages = &tblockages * Atable;
         let EncQBlockages = (
@@ -515,8 +531,8 @@ impl BridgeAuth {
         );
 
         let EncQ = (
-            EncQHc.0 + EncQId.0 + EncQBucket.0 + EncQBlockages.0,
-            EncQHc.1 + EncQId.1 + EncQBucket.1 + EncQBlockages.1,
+            EncQHc.0 + EncQId.0 + EncQBucket.0 + EncQInvRemain.0 + EncQBlockages.0,
+            EncQHc.1 + EncQId.1 + EncQBucket.1 + EncQInvRemain.1 + EncQBlockages.1,
         );
 
         let mut transcript = Transcript::new(b"blockage migration issuing");
@@ -537,15 +553,17 @@ impl BridgeAuth {
                 Xblockages: &self.lox_pub.X[6],
                 Plevel: &(trust_level * P),
                 Psince: &(level_since * P),
-                Pinvremain: &(invremain * P),
                 TId: &TId,
                 TBucket: &TBucket,
+                TInvRemain: &TInvRemain,
                 TBlockages: &TBlockages,
                 D: &req.D,
                 EncId0: &EncId.0,
                 EncId1: &EncId.1,
                 EncBucket0: &req.EncBucket.0,
                 EncBucket1: &req.EncBucket.1,
+                EncInvRemain0: &EncInvRemain.0,
+                EncInvRemain1: &EncInvRemain.1,
                 EncBlockages0: &req.EncBlockages.0,
                 EncBlockages1: &req.EncBlockages.1,
                 x0: &self.lox_priv.x[0],
@@ -560,6 +578,7 @@ impl BridgeAuth {
                 b: &b,
                 tid: &tid,
                 tbucket: &tbucket,
+                tinvremain: &tinvremain,
                 tblockages: &tblockages,
             },
         )
@@ -569,9 +588,11 @@ impl BridgeAuth {
             level_since,
             P,
             EncQ,
+            EncInvRemain,
             id_server,
             TId,
             TBucket,
+            TInvRemain,
             TBlockages,
             piBlindIssue,
         })
@@ -613,6 +634,13 @@ pub fn handle_response(
     // moving from level i to level i+1)
     let invremain: Scalar = LEVEL_INVITATIONS[(new_level - 1) as usize].into();
 
+    // Decrypt EncInvRemain
+    let recv_invremain = resp.EncInvRemain.1 - (state.d * resp.EncInvRemain.0);
+
+    if recv_invremain != &invremain * Btable {
+        return Err(ProofError::VerificationFailure);
+    }
+
     // Verify the proof
     let mut transcript = Transcript::new(b"blockage migration issuing");
     blindissue::verify_compact(
@@ -633,15 +661,17 @@ pub fn handle_response(
             Xblockages: &lox_pub.X[6].compress(),
             Plevel: &(state.trust_level * resp.P).compress(),
             Psince: &(resp.level_since * resp.P).compress(),
-            Pinvremain: &(invremain * resp.P).compress(),
             TId: &resp.TId.compress(),
             TBucket: &resp.TBucket.compress(),
+            TInvRemain: &resp.TInvRemain.compress(),
             TBlockages: &resp.TBlockages.compress(),
             D: &state.D.compress(),
             EncId0: &EncId.0.compress(),
             EncId1: &EncId.1.compress(),
             EncBucket0: &state.EncBucket.0.compress(),
             EncBucket1: &state.EncBucket.1.compress(),
+            EncInvRemain0: &resp.EncInvRemain.0.compress(),
+            EncInvRemain1: &resp.EncInvRemain.1.compress(),
             EncBlockages0: &state.EncBlockages.0.compress(),
             EncBlockages1: &state.EncBlockages.1.compress(),
         },