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https://gogs.blitter.com/RLabs/xs
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132 lines
3.2 KiB
Go
132 lines
3.2 KiB
Go
/* Herradura - a Key exchange scheme in the style of Diffie-Hellman Key Exchange.
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Copyright (C) 2017 Omar Alejandro Herrera Reyna
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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golang implementation by Russ Magee (rmagee_at_gmail.com) */
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package herradurakex
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import (
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"fmt"
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"math/big"
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"math/rand"
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"time"
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)
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// This type holds the session state for a key exchange
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type HerraduraKEx struct {
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intSz, pubSz int
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randctx *rand.Rand
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a *big.Int
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b *big.Int
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d, PeerD *big.Int
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fa *big.Int
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}
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// Returns a new HerraduraKEx struct
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func New(i int, p int) (h *HerraduraKEx) {
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h = new(HerraduraKEx)
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h.intSz = i
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h.pubSz = p
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h.seed()
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h.a = h.rand()
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h.b = h.rand()
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h.d = h.fscxRevolve(h.a, h.b, h.pubSz)
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return h
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}
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func (h *HerraduraKEx) seed() {
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r := rand.New(rand.NewSource(time.Now().UnixNano()))
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h.randctx = r
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}
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func (h *HerraduraKEx) rand() (v *big.Int) {
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v = big.NewInt(0)
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v.Rand(h.randctx, h.getMax())
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return v
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}
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// Return max value for an n-bit big.Int
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func (h *HerraduraKEx) getMax() (v *big.Int) {
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v = big.NewInt(0)
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var max big.Int
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for i := 0; i < h.intSz; i++ {
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max.SetBit(v, i, 1)
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}
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v = &max
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return v
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}
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func (h *HerraduraKEx) bitX(x *big.Int, pos int) (ret int64) {
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if pos < 0 {
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pos = h.intSz - pos
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}
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if pos == 0 {
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ret = int64(x.Bit(1) ^ x.Bit(0) ^ x.Bit(h.intSz-1))
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} else if pos == h.intSz-1 {
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ret = int64(x.Bit(0) ^ x.Bit(pos) ^ x.Bit(pos-1))
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} else {
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ret = int64(x.Bit((pos+1)%h.intSz) ^ x.Bit(pos) ^ x.Bit(pos-1))
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}
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return ret
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}
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func (h *HerraduraKEx) bit(up, down *big.Int, posU, posD int) (ret *big.Int) {
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return big.NewInt(h.bitX(up, posU) ^ h.bitX(down, posD))
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}
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func (h *HerraduraKEx) fscx(up, down *big.Int) (result *big.Int) {
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result = big.NewInt(0)
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for count := 0; count < h.intSz; count++ {
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result.Lsh(result, 1)
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result.Add(result, h.bit(up, down, count, count))
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}
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return result
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}
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// This is the iteration function using the result of the previous iteration as the first
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// parameter and the second parameter of the first iteration
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func (h *HerraduraKEx) fscxRevolve(x, y *big.Int, passes int) (result *big.Int) {
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result = big.NewInt(0)
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result = x
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for count := 0; count < passes; count++ {
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result = h.fscx(result, y)
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}
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return result
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}
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func (h *HerraduraKEx) D() *big.Int {
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return h.d
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}
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func (h *HerraduraKEx) FA() {
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h.fa = h.fscxRevolve(h.PeerD, h.b, h.intSz-h.pubSz)
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h.fa.Xor(h.fa, h.a)
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}
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func (h *HerraduraKEx) String() string {
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return fmt.Sprintf("s:%d p:%d\na:%s\nb:%s\nd:->%s\n<-PeerD:%s\nfa:%s",
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h.intSz, h.pubSz,
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h.a.Text(16), h.b.Text(16),
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h.d.Text(16),
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h.PeerD.Text(16),
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h.fa.Text(16))
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}
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