secp256k1: Return normalized val from DecompressY.

dcrec/secp256k1/curve.go

@@ -1285,8 +1285,13 @@ func isOnCurve(fx, fy *FieldVal) bool {
 // based on the desired oddness and returns whether or not it was successful
 // since not all X coordinates are valid.
 //
-// The magnitude of the provided X coordinate field val must be a max of 8 for a
-// correct result.  The resulting Y field val will have a max magnitude of 2.
+// The magnitude of the provided X coordinate field value must be a max of 8 for
+// a correct result.  The resulting Y field value will have a magnitude of 1.
+//
+//	Preconditions:
+//	  - The input field value MUST have a max magnitude of 8
+//	Output Normalized: Yes if the func returns true, no otherwise
+//	Output Max Magnitude: 1
 func DecompressY(x *FieldVal, odd bool, resultY *FieldVal) bool {
 	// The curve equation for secp256k1 is: y^2 = x^3 + 7.  Thus
 	// y = +-sqrt(x^3 + 7).
@@ -1299,7 +1304,7 @@ func DecompressY(x *FieldVal, odd bool, resultY *FieldVal) bool {
 		return false
 	}
 	if resultY.Normalize().IsOdd() != odd {
-		resultY.Negate(1)
+		resultY.Negate(1).Normalize()
 	}
 	return true
 }

dcrec/secp256k1/curve_test.go

@@ -1194,7 +1194,6 @@ func TestDecompressY(t *testing.T) {
 		}
 
 		// Ensure the decompressed odd Y coordinate is the expected value.
-		oddY.Normalize()
 		wantOddY := new(FieldVal).SetHex(test.wantOddY)
 		if !wantOddY.Equals(&oddY) {
 			t.Errorf("%s: mismatched odd y\ngot: %v, want: %v", test.name,
@@ -1203,7 +1202,6 @@ func TestDecompressY(t *testing.T) {
 		}
 
 		// Ensure the decompressed even Y coordinate is the expected value.
-		evenY.Normalize()
 		wantEvenY := new(FieldVal).SetHex(test.wantEvenY)
 		if !wantEvenY.Equals(&evenY) {
 			t.Errorf("%s: mismatched even y\ngot: %v, want: %v", test.name,
@@ -1264,8 +1262,6 @@ func TestDecompressYRandom(t *testing.T) {
 
 		// Ensure that the resulting y coordinates match their respective
 		// expected oddness.
-		oddY.Normalize()
-		evenY.Normalize()
 		if !oddY.IsOdd() {
 			t.Fatalf("requested odd y is even for x = %v", x)
 		}

dcrec/secp256k1/ecdsa/signature.go

@@ -1,5 +1,5 @@
 // Copyright (c) 2013-2014 The btcsuite developers
-// Copyright (c) 2015-2022 The Decred developers
+// Copyright (c) 2015-2024 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -931,6 +931,7 @@ func RecoverCompact(signature, hash []byte) (*secp256k1.PublicKey, bool, error)
 		// r = r + N (mod P)
 		fieldR.Add(&orderAsFieldVal)
 	}
+	fieldR.Normalize()
 
 	// Step 4.
 	//
@@ -952,8 +953,8 @@ func RecoverCompact(signature, hash []byte) (*secp256k1.PublicKey, bool, error)
 	//
 	// X = (r, y)
 	var X secp256k1.JacobianPoint
-	X.X.Set(fieldR.Normalize())
-	X.Y.Set(y.Normalize())
+	X.X.Set(&fieldR)
+	X.Y.Set(&y)
 	X.Z.SetInt(1)
 
 	// Step 6.

dcrec/secp256k1/pubkey.go

@@ -1,5 +1,5 @@
 // Copyright (c) 2013-2014 The btcsuite developers
-// Copyright (c) 2015-2022 The Decred developers
+// Copyright (c) 2015-2024 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -177,7 +177,6 @@ func ParsePubKey(serialized []byte) (key *PublicKey, err error) {
 				"the secp256k1 curve", x)
 			return nil, makeError(ErrPubKeyNotOnCurve, str)
 		}
-		y.Normalize()
 
 	default:
 		str := fmt.Sprintf("malformed public key: invalid length: %d",