1 files changed, 29 insertions, 0 deletions
diff --git a/src/crypto/elliptic/nistec_p256.go b/src/crypto/elliptic/nistec_p256.go
new file mode 100644
index 0000000..304f8f2
--- /dev/null
+++ b/src/crypto/elliptic/nistec_p256.go
@@ -0,0 +1,29 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build amd64 || arm64
+
+package elliptic
+
+import (
+	"crypto/internal/nistec"
+	"math/big"
+)
+
+func (c p256Curve) Inverse(k *big.Int) *big.Int {
+	if k.Sign() < 0 {
+		// This should never happen.
+		k = new(big.Int).Neg(k)
+	}
+	if k.Cmp(c.params.N) >= 0 {
+		// This should never happen.
+		k = new(big.Int).Mod(k, c.params.N)
+	}
+	scalar := k.FillBytes(make([]byte, 32))
+	inverse, err := nistec.P256OrdInverse(scalar)
+	if err != nil {
+		panic("crypto/elliptic: nistec rejected normalized scalar")
+	}
+	return new(big.Int).SetBytes(inverse)
+}