Compute RecoveryId() in ecdsa.Signature.

taurushq-io · Nov 23, 2022 · d44e983 · d44e983
1 parent 1c20cbb
commit d44e983
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Showing 2 changed files with 21 additions and 0 deletions.
diff --git a/pkg/ecdsa/signature.go b/pkg/ecdsa/signature.go
@@ -27,3 +27,20 @@ func (sig Signature) Verify(X curve.Point, hash []byte) bool {
 	R2 = sInv.Act(R2)
 	return R2.Equal(sig.R)
 }
+
+func (sig Signature) RecoveryId() byte {
+	r := sig.R.(*curve.Secp256k1Point)
+	s := sig.S.(*curve.Secp256k1Scalar)
+
+	var recid byte = 0
+
+	if !r.HasEvenY() {
+		recid = 1;
+	}
+
+	if s.Value().IsOverHalfOrder() {
+		recid ^= 1
+	}
+
+	return recid
+}
diff --git a/pkg/math/curve/secp256k1.go b/pkg/math/curve/secp256k1.go
@@ -83,6 +83,10 @@ func (*Secp256k1Scalar) Curve() Curve {
 	return Secp256k1{}
 }
 
+func (s *Secp256k1Scalar) Value() *secp256k1.ModNScalar {
+	return &s.value
+}
+
 func (s *Secp256k1Scalar) MarshalBinary() ([]byte, error) {
 	data := s.value.Bytes()
 	return data[:], nil