DESアルゴリズムC言語実装
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DESアルゴリズムC言語実装
アルゴリズムの概要
DESアルゴリズムは対称ブロック暗号化法であり,暗号化と復号化の両方に長さ64ビットの鍵を用いる.64ビットを1パケット長とし、各パケットについて、置換、Feistel輪関数、サブ鍵生成などの一連の動作により、64ビットの暗号文を出力する.復号中は,サブキー入力の順序を交換することで,元の明文を解くことができる.
全体構造入力された64ビット暗号文を一度IP置換してL 0 R 0 L_を得る0R_0 L0R0 はIP置換の結果を16回反復し,反復の規則はL i=R(i−1),R i=L(i−1)f(R(i−1),K i)L_である.i = R_(i-1), R_i = L_(i-1)\bigoplus f(R_(i-1),K_i) Li=R(i−1),Ri=L(i−1)⨁f(R(i−1),Ki) サブ鍵の生成は入力された64鍵を元にPC 1置換,循環シフト,PC 2置換などの過程を経て16個の48ビットのワード鍵を生成し,Feistel関数に順次入力する. 16回の反復が完了した後、前32ビットと後32ビットの交換位置をIP逆置換し、最終的な暗号文を得る.
コード実装 tables.h:DESアルゴリズムプロセスで使用されるすべての配列を定義する utility.h:すべてのモジュール関数の定義と実装 main.cpp:入出力を処理します.
アルゴリズムの概要
DESアルゴリズムは対称ブロック暗号化法であり,暗号化と復号化の両方に長さ64ビットの鍵を用いる.64ビットを1パケット長とし、各パケットについて、置換、Feistel輪関数、サブ鍵生成などの一連の動作により、64ビットの暗号文を出力する.復号中は,サブキー入力の順序を交換することで,元の明文を解くことができる.
全体構造
コード実装
#pragma once
#include
int IP_Table[64] = {
58, 50, 42, 34, 26, 18, 10, 2,
60, 52, 44, 36, 28, 20, 12, 4,
62, 54, 46, 38, 30, 22, 14, 6,
64, 56, 48, 40, 32, 24, 16, 8,
57, 49, 41, 33, 25, 17, 9, 1,
59, 51, 43, 35, 27, 19, 11, 3,
61, 53, 45, 37, 29, 21, 13, 5,
63, 55, 47, 39, 31, 23, 15, 7 };
int IP_Reverse_Table[64] = {
40, 8, 48, 16, 56, 24, 64, 32,
39, 7, 47, 15, 55, 23, 63, 31,
38, 6, 46, 14, 54, 22, 62, 30,
37, 5, 45, 13, 53, 21, 61, 29,
36, 4, 44, 12, 52, 20, 60, 28,
35, 3, 43, 11, 51, 19, 59, 27,
34, 2, 42, 10, 50, 18, 58, 26,
33, 1, 41, 9, 49, 17, 57, 25 };
int Extension_Table[48] = {
32, 1, 2, 3, 4, 5,
4, 5, 6, 7, 8, 9,
8, 9, 10, 11, 12, 13,
12, 13, 14, 15, 16, 17,
16, 17, 18, 19, 20, 21,
20, 21, 22, 23, 24, 25,
24, 25, 26, 27, 28, 29,
28, 29, 30, 31, 32, 1 };
int S_Box[8][64] = {
{
14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
0, 15, 7, 4, 15, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13
},
{
15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,
3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9
},
{
10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,
13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12
},
{
7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,
12, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14
},
{
2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,
14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3
},
{
12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,
10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13
},
{
4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,
13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12
},
{
13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,
1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11
}
};
int PC1_Table[56] = {
57, 49, 41, 33, 25, 17, 9,
1, 58, 50, 42, 34, 26, 18,
10, 2, 59, 51, 43, 35, 27,
19, 11, 3, 60, 52, 44, 36,
63, 55, 47, 39, 31, 23, 15,
7, 62, 54, 46, 38, 30, 22,
14, 6, 61, 53, 45, 37, 29,
21, 13, 5, 28, 20, 12, 4 };
int PC2_Table[48] = {
14, 17, 11, 24, 1, 5,
3, 28, 15, 6, 21, 10,
23, 19, 12, 4, 26, 8,
16, 7, 27, 20, 13, 2,
41, 52, 31, 37, 47, 55,
30, 40, 51, 45, 33, 48,
44, 49, 39, 56, 34, 53,
46, 42, 50, 36, 29, 32
};
int P_Table[32] = {
16, 7, 20, 21,
29, 12, 28, 17,
1, 15, 23, 26,
5, 18, 31, 10,
2, 8, 24, 14,
32, 27, 3, 9,
19, 13, 30, 6,
22, 11, 4, 25
};
#pragma once
#include "tables.h"
void charToBit(char * msg, int* msgBit) {
for (int i = 0; i < 8; i++) {
for (int j = 0; j < 8; j++) {
msgBit[(i + 1) * 8 - j - 1] = (msg[i] >> j) & 1;
}
}
}
void BitToChar(int* msgBit, char* msg) {
int sum = 0;
int count = 0;
for (int i = 0; i < 64; i++) {
sum = sum * 2 + msgBit[i];
if (i % 8 == 7) {
msg[count++] = sum;
sum = 0;
}
}
}
void IP_Permutation(int* input, int* output) {
for (int i = 0; i < 64; i++) {
output[i] = input[IP_Table[i] - 1];
}
}
void IP_Reverse_Permutation(int* input, int* output) {
for (int i = 0; i < 64; i++) {
output[i] = input[IP_Reverse_Table[i] - 1];
}
}
void devision(int* input, int *L, int* R) {
for (int i = 0; i < 32; i++) {
L[i] = input[i];
R[i] = input[i + 32];
}
}
void Extension(int* R, int* extendedR) {
for (int i = 0; i < 48; i++) {
extendedR[i] = R[Extension_Table[i] - 1];
}
}
void Xor48(int* R, int* subkey) {
for (int i = 0; i < 48; i++) {
if (R[i] != subkey[i]) {
R[i] = 1;
}
else {
R[i] = 0;
}
}
}
void Xor32(int* R, int* subkey) {
for (int i = 0; i < 32; i++) {
if (R[i] != subkey[i]) {
R[i] = 1;
}
else {
R[i] = 0;
}
}
}
void SBox(int* input, int start, int* output, int* SBox) {
int row = input[start] * 2 + input[start + 5];
int col = 0;
for (int i = 1; i <= 4; i++) {
col = col * 2 + input[start + i];
}
int result = SBox[row * 16 + col];
for (int i = 0; i < 4; i++) {
output[3 - i] = (result >> i) & 1;
}
}
void P_Permutation(int* input, int* output) {
for (int i = 0; i < 32; i++) {
output[i] = input[P_Table[i] - 1];
}
}
void Feistel(int* R, int* subkey, int* output) {
int extendedR[48] = { 0 };
Extension(R, extendedR);
Xor48(extendedR, subkey);
int SBoxResult[8][4] = { 0 };
for (int i = 0; i < 8; i++) {
SBox(extendedR, i * 6, SBoxResult[i], S_Box[i]);
}
// SBox
int totalSBox[32] = { 0 };
for (int i = 0; i < 32; i++) {
totalSBox[i] = SBoxResult[i / 4][i % 4];
}
P_Permutation(totalSBox, output);
}
void leftShift(int* input) {
int first = input[0];
for (int i = 0; i < 27; i++) {
input[i] = input[i + 1];
}
input[27] = first;
}
void PC1(int* input, int* key) {
for (int i = 0; i < 56; i++) {
input[i] = key[PC1_Table[i] - 1];
}
}
void PC2(int* input, int* subkey) {
for (int i = 0; i < 48; i++) {
subkey[i] = input[PC2_Table[i] - 1];
}
}
void generateSubkeys(int key[64], int subkeys[16][48]) {
int pc1[56] = { 0 };
int pc2[56] = { 0 };
int C[28] = { 0 };
int D[28] = { 0 };
PC1(pc1, key);
for (int i = 0; i < 28; i++) {
C[i] = pc1[i];
D[i] = pc1[i + 28];
}
for (int i = 1; i < 17; i++) {
if (i == 1 || i == 2 || i == 9 || i == 16) {
leftShift(C);
leftShift(D);
}
else {
leftShift(C);
leftShift(C);
leftShift(D);
leftShift(D);
}
for (int i = 0; i < 28; i++) {
pc2[i] = C[i];
pc2[i + 28] = D[i];
}
PC2(pc2, subkeys[i - 1]);
}
}
void Swap(int* L, int * R) {
int* temp = L;
L = R;
R = temp;
}
void DES(int* msgBit, char* key) {
int keyBit[64] = { 0 };
int permutationBit[64] = { 0 }; //IP
int L[32] = { 0 }; // 32
int R[32] = { 0 }; // 32
int subkeys[16][48] = { 0 };
int iterationL[32] = { 0 }; // L R
int iterationR[32] = { 0 };
int cryptedMsg[64] = { 0 };
charToBit(key, keyBit);
IP_Permutation(msgBit, permutationBit);
devision(permutationBit, L, R);
generateSubkeys(keyBit, subkeys);
// T
int FeistelResult[32] = { 0 };
for (int i = 0; i < 16; i++) {
for (int j = 0; j < 32; j++) {
iterationL[j] = R[j];
iterationR[j] = L[j];
}
Feistel(R, subkeys[i], FeistelResult);
Xor32(iterationR, FeistelResult);
for (int j = 0; j < 32; j++) {
L[j] = iterationL[j];
R[j] = iterationR[j];
}
}
// L R
int iterationTotal[64] = { 0 }; //
for (int i = 0; i < 32; i++) {
iterationTotal[i] = iterationR[i];
iterationTotal[i + 32] = iterationL[i];
}
IP_Reverse_Permutation(iterationTotal, cryptedMsg);
printf("
The crypeted message is :
");
for (int i = 0; i < 64; i++) {
printf("%d", cryptedMsg[i]);
}
}
void Decrypt(int* msgBit, char* key) {
int keyBit[64] = { 0 };
int permutationBit[64] = { 0 }; //IP
int L[32] = { 0 }; // 32
int R[32] = { 0 }; // 32
int subkeys[16][48] = { 0 };
int iterationL[32] = { 0 }; // L R
int iterationR[32] = { 0 };
int decryptedBit[64] = { 0 };
charToBit(key, keyBit);
IP_Permutation(msgBit, permutationBit);
devision(permutationBit, L, R);
generateSubkeys(keyBit, subkeys);
// T
int FeistelResult[32] = { 0 };
for (int i = 0; i < 16; i++) {
for (int j = 0; j < 32; j++) {
iterationL[j] = R[j];
iterationR[j] = L[j];
}
Feistel(R, subkeys[15 - i], FeistelResult);
Xor32(iterationR, FeistelResult);
for (int j = 0; j < 32; j++) {
L[j] = iterationL[j];
R[j] = iterationR[j];
}
}
// L R 。
int iterationTotal[64] = { 0 };
for (int i = 0; i < 32; i++) {
iterationTotal[i] = iterationR[i];
iterationTotal[i + 32] = iterationL[i];
}
IP_Reverse_Permutation(iterationTotal, decryptedBit);
char decryptedMsg[9] = { 0 };
BitToChar(decryptedBit, decryptedMsg);
printf("
The decrypeted message is :
");
for (int i = 0; i < 8; i++) {
printf("%c", decryptedMsg[i]);
}
printf("
");
}
#include
#include
#include "utility.h"
int main() {
char msg[9] = { 0 };
char key[9] = { 0 };
int msgBit[64] = { 0 };
char cryptedMsg[65] = { 0 };
int cryptedMsgBit[64] = { 0 };
printf("Encrypting process
");
printf("Please enter the message:");
gets_s(msg);
printf("Please enter the key:");
gets_s(key);
charToBit(msg, msgBit);
DES(msgBit, key);
printf("
Decrypting process
");
printf("Please enter the crypted message:
");
gets_s(cryptedMsg);
for (int i = 0; i < 64; i++) {
cryptedMsgBit[i] = cryptedMsg[i] - '0';
}
printf("Please enter the key:");
gets_s(key);
Decrypt(cryptedMsgBit,key);
system("pause");
return 0;
}