Current File : //usr/local/go119/src/crypto/internal/nistec/fiat/p224_invert.go
// 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 *P224Element) Invert(x *P224Element) *P224Element {
// Inversion is implemented as exponentiation with exponent p − 2.
// The sequence of 11 multiplications and 223 squarings is derived from the
// following addition chain generated with github.com/mmcloughlin/addchain v0.3.0.
//
// _10 = 2*1
// _11 = 1 + _10
// _110 = 2*_11
// _111 = 1 + _110
// _111000 = _111 << 3
// _111111 = _111 + _111000
// x12 = _111111 << 6 + _111111
// x14 = x12 << 2 + _11
// x17 = x14 << 3 + _111
// x31 = x17 << 14 + x14
// x48 = x31 << 17 + x17
// x96 = x48 << 48 + x48
// x127 = x96 << 31 + x31
// return x127 << 97 + x96
//
var z = new(P224Element).Set(e)
var t0 = new(P224Element)
var t1 = new(P224Element)
var t2 = new(P224Element)
z.Square(x)
t0.Mul(x, z)
z.Square(t0)
z.Mul(x, z)
t1.Square(z)
for s := 1; s < 3; s++ {
t1.Square(t1)
}
t1.Mul(z, t1)
t2.Square(t1)
for s := 1; s < 6; s++ {
t2.Square(t2)
}
t1.Mul(t1, t2)
for s := 0; s < 2; s++ {
t1.Square(t1)
}
t0.Mul(t0, t1)
t1.Square(t0)
for s := 1; s < 3; s++ {
t1.Square(t1)
}
z.Mul(z, t1)
t1.Square(z)
for s := 1; s < 14; s++ {
t1.Square(t1)
}
t0.Mul(t0, t1)
t1.Square(t0)
for s := 1; s < 17; s++ {
t1.Square(t1)
}
z.Mul(z, t1)
t1.Square(z)
for s := 1; s < 48; s++ {
t1.Square(t1)
}
z.Mul(z, t1)
t1.Square(z)
for s := 1; s < 31; s++ {
t1.Square(t1)
}
t0.Mul(t0, t1)
for s := 0; s < 97; s++ {
t0.Square(t0)
}
z.Mul(z, t0)
return e.Set(z)
}
Mini Shell