mirror of
https://github.com/autc04/Retro68.git
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74 lines
1.9 KiB
Go
74 lines
1.9 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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//go:build ignore
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package main
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import (
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"crypto/elliptic"
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"encoding/binary"
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"log"
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"os"
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)
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func main() {
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// Generate precomputed p256 tables.
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var pre [43][32 * 8]uint64
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basePoint := []uint64{
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0x79e730d418a9143c, 0x75ba95fc5fedb601, 0x79fb732b77622510, 0x18905f76a53755c6,
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0xddf25357ce95560a, 0x8b4ab8e4ba19e45c, 0xd2e88688dd21f325, 0x8571ff1825885d85,
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0x0000000000000001, 0xffffffff00000000, 0xffffffffffffffff, 0x00000000fffffffe,
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}
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t1 := make([]uint64, 12)
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t2 := make([]uint64, 12)
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copy(t2, basePoint)
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zInv := make([]uint64, 4)
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zInvSq := make([]uint64, 4)
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for j := 0; j < 32; j++ {
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copy(t1, t2)
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for i := 0; i < 43; i++ {
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// The window size is 6 so we need to double 6 times.
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if i != 0 {
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for k := 0; k < 6; k++ {
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elliptic.P256PointDoubleAsm(t1, t1)
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}
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}
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// Convert the point to affine form. (Its values are
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// still in Montgomery form however.)
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elliptic.P256Inverse(zInv, t1[8:12])
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elliptic.P256Sqr(zInvSq, zInv, 1)
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elliptic.P256Mul(zInv, zInv, zInvSq)
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elliptic.P256Mul(t1[:4], t1[:4], zInvSq)
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elliptic.P256Mul(t1[4:8], t1[4:8], zInv)
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copy(t1[8:12], basePoint[8:12])
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// Update the table entry
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copy(pre[i][j*8:], t1[:8])
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}
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if j == 0 {
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elliptic.P256PointDoubleAsm(t2, basePoint)
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} else {
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elliptic.P256PointAddAsm(t2, t2, basePoint)
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}
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}
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var bin []byte
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// Dump the precomputed tables, flattened, little-endian.
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// These tables are used directly by assembly on little-endian platforms.
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// go:embedding the data into a string lets it be stored readonly.
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for i := range &pre {
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for _, v := range &pre[i] {
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var u8 [8]byte
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binary.LittleEndian.PutUint64(u8[:], v)
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bin = append(bin, u8[:]...)
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}
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}
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err := os.WriteFile("p256_asm_table.bin", bin, 0644)
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if err != nil {
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log.Fatal(err)
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}
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}
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