102 lines
2.1 KiB
Go
102 lines
2.1 KiB
Go
// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Code generated by addchain. DO NOT EDIT.
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package fiat
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// Invert sets e = 1/x, and returns e.
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//
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// If x == 0, Invert returns e = 0.
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func (e *P384Element) Invert(x *P384Element) *P384Element {
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// Inversion is implemented as exponentiation with exponent p − 2.
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// The sequence of 15 multiplications and 383 squarings is derived from the
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// following addition chain generated with github.com/mmcloughlin/addchain v0.3.0.
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//
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// _10 = 2*1
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// _11 = 1 + _10
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// _110 = 2*_11
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// _111 = 1 + _110
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// _111000 = _111 << 3
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// _111111 = _111 + _111000
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// x12 = _111111 << 6 + _111111
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// x24 = x12 << 12 + x12
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// x30 = x24 << 6 + _111111
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// x31 = 2*x30 + 1
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// x32 = 2*x31 + 1
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// x63 = x32 << 31 + x31
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// x126 = x63 << 63 + x63
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// x252 = x126 << 126 + x126
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// x255 = x252 << 3 + _111
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// i397 = ((x255 << 33 + x32) << 94 + x30) << 2
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// return 1 + i397
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//
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var z = new(P384Element).Set(e)
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var t0 = new(P384Element)
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var t1 = new(P384Element)
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var t2 = new(P384Element)
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var t3 = new(P384Element)
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z.Square(x)
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z.Mul(x, z)
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z.Square(z)
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t1.Mul(x, z)
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z.Square(t1)
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for s := 1; s < 3; s++ {
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z.Square(z)
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}
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z.Mul(t1, z)
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t0.Square(z)
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for s := 1; s < 6; s++ {
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t0.Square(t0)
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}
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t0.Mul(z, t0)
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t2.Square(t0)
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for s := 1; s < 12; s++ {
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t2.Square(t2)
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}
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t0.Mul(t0, t2)
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for s := 0; s < 6; s++ {
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t0.Square(t0)
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}
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z.Mul(z, t0)
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t0.Square(z)
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t2.Mul(x, t0)
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t0.Square(t2)
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t0.Mul(x, t0)
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t3.Square(t0)
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for s := 1; s < 31; s++ {
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t3.Square(t3)
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}
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t2.Mul(t2, t3)
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t3.Square(t2)
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for s := 1; s < 63; s++ {
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t3.Square(t3)
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}
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t2.Mul(t2, t3)
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t3.Square(t2)
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for s := 1; s < 126; s++ {
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t3.Square(t3)
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}
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t2.Mul(t2, t3)
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for s := 0; s < 3; s++ {
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t2.Square(t2)
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}
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t1.Mul(t1, t2)
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for s := 0; s < 33; s++ {
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t1.Square(t1)
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}
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t0.Mul(t0, t1)
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for s := 0; s < 94; s++ {
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t0.Square(t0)
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}
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z.Mul(z, t0)
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for s := 0; s < 2; s++ {
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z.Square(z)
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}
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z.Mul(x, z)
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return e.Set(z)
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}
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