1 files changed, 89 insertions, 0 deletions
diff --git a/src/crypto/internal/nistec/fiat/p521_invert.go b/src/crypto/internal/nistec/fiat/p521_invert.go
new file mode 100644
index 0000000..16c53e1
--- /dev/null
+++ b/src/crypto/internal/nistec/fiat/p521_invert.go
@@ -0,0 +1,89 @@
+// Copyright 2021 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.
+
+// Code generated by addchain. DO NOT EDIT.
+
+package fiat
+
+// Invert sets e = 1/x, and returns e.
+//
+// If x == 0, Invert returns e = 0.
+func (e *P521Element) Invert(x *P521Element) *P521Element {
+	// Inversion is implemented as exponentiation with exponent p − 2.
+	// The sequence of 13 multiplications and 520 squarings is derived from the
+	// following addition chain generated with github.com/mmcloughlin/addchain v0.4.0.
+	//
+	//	_10       = 2*1
+	//	_11       = 1 + _10
+	//	_1100     = _11 << 2
+	//	_1111     = _11 + _1100
+	//	_11110000 = _1111 << 4
+	//	_11111111 = _1111 + _11110000
+	//	x16       = _11111111 << 8 + _11111111
+	//	x32       = x16 << 16 + x16
+	//	x64       = x32 << 32 + x32
+	//	x65       = 2*x64 + 1
+	//	x129      = x65 << 64 + x64
+	//	x130      = 2*x129 + 1
+	//	x259      = x130 << 129 + x129
+	//	x260      = 2*x259 + 1
+	//	x519      = x260 << 259 + x259
+	//	return      x519 << 2 + 1
+	//
+
+	var z = new(P521Element).Set(e)
+	var t0 = new(P521Element)
+
+	z.Square(x)
+	z.Mul(x, z)
+	t0.Square(z)
+	for s := 1; s < 2; s++ {
+		t0.Square(t0)
+	}
+	z.Mul(z, t0)
+	t0.Square(z)
+	for s := 1; s < 4; s++ {
+		t0.Square(t0)
+	}
+	z.Mul(z, t0)
+	t0.Square(z)
+	for s := 1; s < 8; s++ {
+		t0.Square(t0)
+	}
+	z.Mul(z, t0)
+	t0.Square(z)
+	for s := 1; s < 16; s++ {
+		t0.Square(t0)
+	}
+	z.Mul(z, t0)
+	t0.Square(z)
+	for s := 1; s < 32; s++ {
+		t0.Square(t0)
+	}
+	z.Mul(z, t0)
+	t0.Square(z)
+	t0.Mul(x, t0)
+	for s := 0; s < 64; s++ {
+		t0.Square(t0)
+	}
+	z.Mul(z, t0)
+	t0.Square(z)
+	t0.Mul(x, t0)
+	for s := 0; s < 129; s++ {
+		t0.Square(t0)
+	}
+	z.Mul(z, t0)
+	t0.Square(z)
+	t0.Mul(x, t0)
+	for s := 0; s < 259; s++ {
+		t0.Square(t0)
+	}
+	z.Mul(z, t0)
+	for s := 0; s < 2; s++ {
+		z.Square(z)
+	}
+	z.Mul(x, z)
+
+	return e.Set(z)
+}