golang
diff --git a/‎src/math/big/arith_test.go
Lines changed: 1 addition & 1 deletion b/‎src/math/big/arith_test.go
Lines changed: 1 addition & 1 deletion
diff --git a/‎src/math/big/int.go
Lines changed: 14 additions & 1 deletion b/‎src/math/big/int.go
Lines changed: 14 additions & 1 deletion
@@ -370,7 +370,7 @@ func TestShiftOverlap(t *testing.T) {
 func TestIssue31084(t *testing.T) {
 	// compute 10^n via 5^n << n.
 	const n = 165
-	p := nat(nil).expNN(nat{5}, nat{n}, nil)
+	p := nat(nil).expNN(nat{5}, nat{n}, nil, false)
 	p = p.shl(p, n)
 	got := string(p.utoa(10))
 	want := "1" + strings.Repeat("0", n)
 
@@ -523,6 +523,14 @@ func (x *Int) TrailingZeroBits() uint {
 // Modular exponentiation of inputs of a particular size is not a
 // cryptographically constant-time operation.
 func (z *Int) Exp(x, y, m *Int) *Int {
+	return z.exp(x, y, m, false)
+}
+
+func (z *Int) expSlow(x, y, m *Int) *Int {
+	return z.exp(x, y, m, true)
+}
+
+func (z *Int) exp(x, y, m *Int, slow bool) *Int {
 	// See Knuth, volume 2, section 4.6.3.
 	xWords := x.abs
 	if y.neg {
@@ -546,7 +554,7 @@ func (z *Int) Exp(x, y, m *Int) *Int {
 		mWords = m.abs // m.abs may be nil for m == 0
 	}
 
-	z.abs = z.abs.expNN(xWords, yWords, mWords)
+	z.abs = z.abs.expNN(xWords, yWords, mWords, slow)
 	z.neg = len(z.abs) > 0 && x.neg && len(yWords) > 0 && yWords[0]&1 == 1 // 0 has no sign
 	if z.neg && len(mWords) > 0 {
 		// make modulus result positive
@@ -879,6 +887,11 @@ func (z *Int) ModInverse(g, n *Int) *Int {
 	return z
 }
 
+func (z nat) modInverse(g, n nat) nat {
+	// TODO(rsc): ModInverse should be implemented in terms of this function.
+	return (&Int{abs: z}).ModInverse(&Int{abs: g}, &Int{abs: n}).abs
+}
+
 // Jacobi returns the Jacobi symbol (x/y), either +1, -1, or 0.
 // The y argument must be an odd integer.
 func Jacobi(x, y *Int) int {