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TDES.cpp
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TDES.cpp
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/***********************************
* Class Name: TDES
* Function: 实现 Triple DES
* ********************************/
#include "TDES.h"
#include <cstring>
#include <iostream>
#include <fstream>
#define ERROR -1
using namespace std;
// 构造函数
TDES::TDES() {
keyRead();
generateKeys();
}
// 读取密钥
void TDES::keyRead() {
ifstream fin("key.dat");
if (!fin) {
cout << "ERROR in opening 'key.dat'";
exit(ERROR);
}
string stmp;
for (int i = 0; i < 3; i++) {
fin >> stmp;
bitset<64> btmp(stmp);
k[i] = btmp;
}
fin.close();
}
// 对 56 位密钥的前后部分进行左移
bitset<28> TDES::leftShift(bitset<28> k, int shift) {
bitset<28> tmp = k;
for (int i = 27; i >= 0; i--) {
if (i - shift < 0) {
k[i] = tmp[i - shift + 28];
} else {
k[i] = tmp[i - shift];
}
}
return k;
}
// 64 位密钥转换为 48 位
void TDES::key64To48(bitset<64> key, bitset<48> subkey[16]) {
bitset<56> realKey;
bitset<48> compressKey;
bitset<28> left, right;
// 去掉奇偶校验位,将 64 位密钥变为 56 位
for (int i = 0; i < 56; i++) {
realKey[55 - i] = key[64 - PC1[i]];
}
// 生成子密钥,保存在 subkey[16] 中
for (int r = 0; r < 16; r++) {
// 前后 28 位处理
for (int i = 28; i < 56; i++) {
left[i - 28] = realKey[i];
}
for (int i = 0; i < 28; i++) {
right[i] = realKey[i];
}
// 左移
left = leftShift(left, SHIFTS[r]);
right = leftShift(right, SHIFTS[r]);
// 压缩置换,由 56 位得到 48 位子密钥
for (int i = 28; i < 56; i++) {
realKey[i] = left[i - 28];
}
for (int i = 0; i < 28; i++) {
realKey[i] = right[i];
}
for (int i = 0; i < 48; i++) {
compressKey[47 - i] = realKey[56 - PC2[i]];
}
subkey[r] = compressKey;
}
}
// 为每一个密钥生成 16 个子密钥,存储在 sk 中
void TDES::generateKeys() {
for (int i = 0; i < 3; i++) {
key64To48(k[i], sk[i]);
}
}
// DES 的 f 函数
bitset<32> TDES::function(bitset<32> A, bitset<48> k) {
bitset<48> EXA;
bitset<32> RES;
// 扩展置换,32 -> 48
for (int i = 0; i < 48; i++) {
EXA[47 - i] = A[32 - E[i]];
}
// 异或
EXA = EXA ^ k;
// 使用 S 盒置换
int x = 0;
for (int i = 0; i < 48; i += 6) {
int row = EXA[47 - i] * 2 + EXA[47 - i - 5];
int col = EXA[46 - i] * 8 + EXA[45 - i] * 4 + EXA[44 - i] * 2 + EXA[43 - i];
int num = SBox[i / 6][row][col];
bitset<4> Sbox(num);
for (int j = 0; j < 4; j++) {
RES[31 - x - j] = Sbox[3 - j];
}
x += 4;
}
// P 置换
bitset<32> tmp = RES;
for (int i = 0; i < 32; i++) {
RES[31 - i] = tmp[32 - P[i]];
}
return RES;
}
// DES 加密(单次加密),n 表示第 n 个密钥(可以为 0,1,2)
bitset<64> TDES::desEncrypt(bitset<64> plaintext, int n) {
bitset<64> currentBits, ciphertext;
bitset<32> left, right, newLeft;
// 初始置换 IP
for (int i = 0; i < 64; i++) {
currentBits[63 - i] = plaintext[64 - IP[i]];
}
// 获取 Li 和 Ri
for (int i = 32; i < 64; i++) {
left[i - 32] = currentBits[i];
}
for (int i = 0; i < 32; i++) {
right[i] = currentBits[i];
}
// 16 轮迭代(子密钥逆序使用)
for (int r = 0; r < 16; r++) {
newLeft = right;
right = left ^ function(right, sk[n][r]);
left = newLeft;
}
// 合并 L16 和 R16,合并为 R16L16
for (int i = 0; i < 32; i++) {
ciphertext[i] = left[i];
}
for (int i = 32; i < 64; i++) {
ciphertext[i] = right[i - 32];
}
// 结尾置换 FP
currentBits = ciphertext;
for (int i = 0; i < 64; i++) {
ciphertext[63 - i] = currentBits[64 - FP[i]];
}
return ciphertext;
}
// DES 解密(单次解密),n 表示第 n 个密钥(可以为 0,1,2)
bitset<64> TDES::desDecrypt(bitset<64> ciphertext, int n) {
bitset<64> plaintext, currentBits;
bitset<32> left, right, newLeft;
// 初始置换 IP
for (int i = 0; i < 64; i++) {
currentBits[63 - i] = ciphertext[64 - IP[i]];
}
// 获取 Li 和 Ri
for (int i = 32; i < 64; i++) {
left[i - 32] = currentBits[i];
}
for (int i = 0; i < 32; i++) {
right[i] = currentBits[i];
}
// 16 轮迭代(子密钥逆序使用)
for (int r = 0; r < 16; r++) {
newLeft = right;
right = left ^ function(right, sk[n][15 - r]);
left = newLeft;
}
// 合并 L16 和 R16,合并为 R16L16
for (int i = 0; i < 32; i++) {
plaintext[i] = left[i];
}
for (int i = 32; i < 64; i++) {
plaintext[i] = right[i - 32];
}
currentBits = plaintext;
for (int i = 0; i < 64; i++) {
plaintext[63 - i] = currentBits[64 - FP[i]];
}
return plaintext;
}
// TDES 加密(三重加密)
bitset<64> TDES::TDESEncrypt() {
cipher = desEncrypt(plain, 0);
cipher = desDecrypt(cipher, 1);
cipher = desEncrypt(cipher, 2);
return cipher;
}
// TDES 解密(三重解密)
bitset<64> TDES::TDESDecrypt() {
plain = desDecrypt(cipher, 2);
plain = desEncrypt(plain, 1);
plain = desDecrypt(plain, 0);
return plain;
}