another edge case (#951)

Author: roynalnaruto

zkevm-circuits/src/sig_circuit.rs

@@ -362,7 +362,7 @@ impl<F: Field> SigCircuit<F> {
         //
         // WARNING: this circuit does not enforce the returned value to be true
         // make sure the caller checks this result!
-        let (sig_is_valid, pk_is_zero, y_coord, y_coord_is_zero) =
+        let (sig_is_valid, pk_is_zero, y_coord) =
             ecdsa_verify_no_pubkey_check::<F, Fp, Fq, Secp256k1Affine>(
                 &ecc_chip.field_chip,
                 ctx,
@@ -426,13 +426,13 @@ impl<F: Field> SigCircuit<F> {
             .range
             .range_check(ctx, &assigned_y_tmp, 87);
 
-        let y_coord_not_zero = gate.not(ctx, QuantumCell::Existing(y_coord_is_zero));
+        let pk_not_zero = gate.not(ctx, QuantumCell::Existing(pk_is_zero));
         let sig_is_valid = gate.and_many(
             ctx,
             vec![
                 QuantumCell::Existing(sig_is_valid),
                 QuantumCell::Existing(y_is_ok),
-                QuantumCell::Existing(y_coord_not_zero),
+                QuantumCell::Existing(pk_not_zero),
             ],
         );
 

zkevm-circuits/src/sig_circuit/ecdsa.rs

@@ -31,12 +31,7 @@ pub(crate) fn ecdsa_verify_no_pubkey_check<F: PrimeField, CF: PrimeField, SF: Pr
     msghash: &CRTInteger<F>,
     var_window_bits: usize,
     fixed_window_bits: usize,
-) -> (
-    AssignedValue<F>,
-    AssignedValue<F>,
-    CRTInteger<F>,
-    AssignedValue<F>,
-)
+) -> (AssignedValue<F>, AssignedValue<F>, CRTInteger<F>)
 where
     GA: CurveAffineExt<Base = CF, ScalarExt = SF>,
 {
@@ -221,6 +216,5 @@ where
         ],
     );
 
-    let y_is_zero = scalar_chip.is_soft_zero(ctx, &sum.y);
-    (res, is_pubkey_zero, sum.y, y_is_zero)
+    (res, is_pubkey_zero, sum.y)
 }

zkevm-circuits/src/sig_circuit/test.rs

@@ -109,7 +109,7 @@ fn test_edge_cases() {
             good_ecrecover_data.2,
             good_ecrecover_data.3,
         ),
-        // 9. cannot recover even if all inputs are valid
+        // 9. valid msg_hash, r, s, v but pubkey not recovered
         (
             word!("0x571b659b539a9da729fca1f2efdd8b07d6a7042e0640ac5ce3a8c5e3445523d7"),
             word!("0x5d14c6d7824ddecc43d307891c4fae49307e370f827fae93e014796665705800"),