golang p384_invert 代码
文件路径：/src/crypto/internal/nistec/fiat/p384_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 *P384Element) Invert(x *P384Element) *P384Element {
/ Inversion is implemented as exponentiation with exponent p − 2.
/ The sequence of 15 multiplications and 383 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
/ x24 = x12 << 12 + x12
/ x30 = x24 << 6 + _111111
/ x31 = 2*x30 + 1
/ x32 = 2*x31 + 1
/ x63 = x32 << 31 + x31
/ x126 = x63 << 63 + x63
/ x252 = x126 << 126 + x126
/ x255 = x252 << 3 + _111
/ i397 = ((x255 << 33 + x32) << 94 + x30) << 2
/ return 1 + i397
/
var z = new(P384Element).Set(e)
var t0 = new(P384Element)
var t1 = new(P384Element)
var t2 = new(P384Element)
var t3 = new(P384Element)
z.Square(x)
z.Mul(x, z)
z.Square(z)
t1.Mul(x, z)
z.Square(t1)
for s := 1; s < 3; s++ {
z.Square(z)
}
z.Mul(t1, z)
t0.Square(z)
for s := 1; s < 6; s++ {
t0.Square(t0)
}
t0.Mul(z, t0)
t2.Square(t0)
for s := 1; s < 12; s++ {
t2.Square(t2)
}
t0.Mul(t0, t2)
for s := 0; s < 6; s++ {
t0.Square(t0)
}
z.Mul(z, t0)
t0.Square(z)
t2.Mul(x, t0)
t0.Square(t2)
t0.Mul(x, t0)
t3.Square(t0)
for s := 1; s < 31; s++ {
t3.Square(t3)
}
t2.Mul(t2, t3)
t3.Square(t2)
for s := 1; s < 63; s++ {
t3.Square(t3)
}
t2.Mul(t2, t3)
t3.Square(t2)
for s := 1; s < 126; s++ {
t3.Square(t3)
}
t2.Mul(t2, t3)
for s := 0; s < 3; s++ {
t2.Square(t2)
}
t1.Mul(t1, t2)
for s := 0; s < 33; s++ {
t1.Square(t1)
}
t0.Mul(t0, t1)
for s := 0; s < 94; 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)
}