数据加密标准 (DES)已被发现容易受到非常强大的攻击，因此，DES 的受欢迎程度略有下降。
DES 是一种分组密码，并以每个 64 位大小的块为单位加密数据，这意味着 64 位纯文本作为 DES 的输入，产生 64 位密文。加密和解密使用相同的算法和密钥，只有细微的差别。密钥长度为 56 位。基本思想如图所示。
_%7C_Set_1_0.jpg)
我们已经提到 DES 使用 56 位密钥。实际上，初始密钥由 64 位组成。然而，在 DES 过程开始之前，密钥的每个第 8 位都被丢弃以生成一个 56 位的密钥。即位位置 8、16、24、32、40、48、56 和 64 被丢弃。
_%7C_Set_1_1.jpg)
因此，丢弃密钥的每 8 位会从原始 64 位密钥生成一个 56 位密钥。
DES 基于密码学的两个基本属性：替换(也称为混淆)和转置(也称为扩散)。 DES 由 16 个步骤组成，每个步骤称为一个回合。每一轮都执行替换和换位的步骤。现在让我们讨论 DES 中的大层次步骤。
- 第一步，将 64 位纯文本块移交给初始排列 (IP)函数。
- 对纯文本执行的初始排列。
- 接下来，初始置换 (IP) 产生置换块的两半；说左纯文本 (LPT) 和右纯文本 (RPT)。
- 现在每个LPT和RPT都要经过16轮加密过程。
- 最后，重新加入 LPT 和 RPT，并对组合块执行最终排列 (FP)
- 此过程的结果产生 64 位密文。
_%7C_Set_1_2.jpg)
初始排列 (IP) –
正如我们所指出的，初始排列 (IP) 只发生一次，并且发生在第一轮之前。它暗示了 IP 中的换位应该如何进行，如图所示。
例如，IP 将原始明文块的第一位替换为原始明文块的第 58 位，第二位替换为原始明文块的第 50 位，依此类推。
这只不过是原始纯文本块的位位置的杂耍。相同的规则适用于图中所示的所有其他位位置。
_%7C_Set_1_3.jpg)
正如我们在 IP 完成后所注意到的，产生的 64 位置换文本块被分成两个半块。每个半块由 32 位组成，而 16 轮中的每一轮又由图中概述的广泛级别步骤组成。
_%7C_Set_1_4.jpg)
步骤 1：关键转换 –
我们已经注意到，通过丢弃初始密钥的每 8 位，将初始 64 位密钥转换为 56 位密钥。因此，每个 56 位密钥都可用。从这个 56 位密钥中，使用称为密钥转换的过程在每一轮中生成不同的 48 位子密钥。为此，56 位密钥被分成两半，每半 28 位。根据回合的不同，这些半部分会向左循环移动一到两个位置。
例如，如果轮数为 1、2、9 或 16，其他轮次仅按位置进行移位，则循环移位由两个位置完成。每轮移位的密钥位数如图所示。
_%7C_Set_1_5.jpg)
经过适当的移位后，56 位中的 48 位被选中。为了选择 56 位中的 48 位，下表显示了下图。例如，移位后，第 14 位移动到第一个位置，第 17 位移动到第二个位置，依此类推。如果我们仔细观察该表，我们会发现它仅包含 48 位位置。位号 18 被丢弃(我们不会在表中找到它)，像其他 7 位一样，将 56 位密钥减少到 48 位密钥。由于密钥转换过程涉及置换以及选择原始 56 位密钥的 48 位子集，因此称为压缩置换。
_%7C_Set_1_6.jpg)
由于这种压缩置换技术，在每一轮中使用不同的密钥位子集。这使得 DES 不容易破解。
步骤 2：扩展排列 –
回想一下，在初始排列之后，我们有两个 32 位纯文本区域，称为左纯文本(LPT)和右纯文本(RPT)。在扩展置换过程中，RPT 从 32 位扩展到 48 位。位也被置换，因此称为扩展置换。这是因为 32 位 RPT 被分成 8 个块，每个块由 4 位组成。然后，将上一步的每个4位块扩展为相应的6位块，即每4位块增加2个位。
_%7C_Set_1_7.jpg)
在创建输出时，此过程会导致输入位的扩展和排列。密钥转换过程将 56 位密钥压缩为 48 位。然后扩展置换过程将 32 位 RPT 扩展到 48 位。现在，48 位密钥与 48 位 RPT 进行 XOR，结果输出被提供给下一步，即 S-Box 替换。
C++
#include
using namespace std;
string hex2bin(string s)
{
// hexadecimal to binary conversion
unordered_map mp;
mp['0'] = "0000";
mp['1'] = "0001";
mp['2'] = "0010";
mp['3'] = "0011";
mp['4'] = "0100";
mp['5'] = "0101";
mp['6'] = "0110";
mp['7'] = "0111";
mp['8'] = "1000";
mp['9'] = "1001";
mp['A'] = "1010";
mp['B'] = "1011";
mp['C'] = "1100";
mp['D'] = "1101";
mp['E'] = "1110";
mp['F'] = "1111";
string bin = "";
for (int i = 0; i < s.size(); i++) {
bin += mp[s[i]];
}
return bin;
}
string bin2hex(string s)
{
// binary to hexadecimal conversion
unordered_map mp;
mp["0000"] = "0";
mp["0001"] = "1";
mp["0010"] = "2";
mp["0011"] = "3";
mp["0100"] = "4";
mp["0101"] = "5";
mp["0110"] = "6";
mp["0111"] = "7";
mp["1000"] = "8";
mp["1001"] = "9";
mp["1010"] = "A";
mp["1011"] = "B";
mp["1100"] = "C";
mp["1101"] = "D";
mp["1110"] = "E";
mp["1111"] = "F";
string hex = "";
for (int i = 0; i < s.length(); i += 4) {
string ch = "";
ch += s[i];
ch += s[i + 1];
ch += s[i + 2];
ch += s[i + 3];
hex += mp[ch];
}
return hex;
}
string permute(string k, int* arr, int n)
{
string per = "";
for (int i = 0; i < n; i++) {
per += k[arr[i] - 1];
}
return per;
}
string shift_left(string k, int shifts)
{
string s = "";
for (int i = 0; i < shifts; i++) {
for (int j = 1; j < 28; j++) {
s += k[j];
}
s += k[0];
k = s;
s = "";
}
return k;
}
string xor_(string a, string b)
{
string ans = "";
for (int i = 0; i < a.size(); i++) {
if (a[i] == b[i]) {
ans += "0";
}
else {
ans += "1";
}
}
return ans;
}
string encrypt(string pt, vector rkb, vector rk)
{
// Hexadecimal to binary
pt = hex2bin(pt);
// Initial Permutation Table
int initial_perm[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 };
// Initial Permutation
pt = permute(pt, initial_perm, 64);
cout << "After initial permutation: " << bin2hex(pt) << endl;
// Splitting
string left = pt.substr(0, 32);
string right = pt.substr(32, 32);
cout << "After splitting: L0=" << bin2hex(left)
<< " R0=" << bin2hex(right) << endl;
// Expansion D-box Table
int exp_d[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 };
// S-box Table
int s[8][4][16] = { { 14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
0, 15, 7, 4, 14, 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,
13, 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 } };
// Straight Permutation Table
int per[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 };
cout << endl;
for (int i = 0; i < 16; i++) {
// Expansion D-box
string right_expanded = permute(right, exp_d, 48);
// XOR RoundKey[i] and right_expanded
string x = xor_(rkb[i], right_expanded);
// S-boxes
string op = "";
for (int i = 0; i < 8; i++) {
int row = 2 * int(x[i * 6] - '0') + int(x[i * 6 + 5] - '0');
int col = 8 * int(x[i * 6 + 1] - '0') + 4 * int(x[i * 6 + 2] - '0') + 2 * int(x[i * 6 + 3] - '0') + int(x[i * 6 + 4] - '0');
int val = s[i][row][col];
op += char(val / 8 + '0');
val = val % 8;
op += char(val / 4 + '0');
val = val % 4;
op += char(val / 2 + '0');
val = val % 2;
op += char(val + '0');
}
// Straight D-box
op = permute(op, per, 32);
// XOR left and op
x = xor_(op, left);
left = x;
// Swapper
if (i != 15) {
swap(left, right);
}
cout << "Round " << i + 1 << " " << bin2hex(left) << " "
<< bin2hex(right) << " " << rk[i] << endl;
}
// Combination
string combine = left + right;
// Final Permutation Table
int final_perm[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 };
// Final Permutation
string cipher = bin2hex(permute(combine, final_perm, 64));
return cipher;
}
int main()
{
// pt is plain text
string pt, key;
/*cout<<"Enter plain text(in hexadecimal): ";
cin>>pt;
cout<<"Enter key(in hexadecimal): ";
cin>>key;*/
pt = "123456ABCD132536";
key = "AABB09182736CCDD";
// Key Generation
// Hex to binary
key = hex2bin(key);
// Parity bit drop table
int keyp[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 };
// getting 56 bit key from 64 bit using the parity bits
key = permute(key, keyp, 56); // key without parity
// Number of bit shifts
int shift_table[16] = { 1, 1, 2, 2,
2, 2, 2, 2,
1, 2, 2, 2,
2, 2, 2, 1 };
// Key- Compression Table
int key_comp[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 };
// Splitting
string left = key.substr(0, 28);
string right = key.substr(28, 28);
vector rkb; // rkb for RoundKeys in binary
vector rk; // rk for RoundKeys in hexadecimal
for (int i = 0; i < 16; i++) {
// Shifting
left = shift_left(left, shift_table[i]);
right = shift_left(right, shift_table[i]);
// Combining
string combine = left + right;
// Key Compression
string RoundKey = permute(combine, key_comp, 48);
rkb.push_back(RoundKey);
rk.push_back(bin2hex(RoundKey));
}
cout << "\nEncryption:\n\n";
string cipher = encrypt(pt, rkb, rk);
cout << "\nCipher Text: " << cipher << endl;
cout << "\nDecryption\n\n";
reverse(rkb.begin(), rkb.end());
reverse(rk.begin(), rk.end());
string text = encrypt(cipher, rkb, rk);
cout << "\nPlain Text: " << text << endl;
} Java
import java.util.*;
class Main {
private static class DES {
// CONSTANTS
// Initial Permutation Table
int[] IP = { 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 };
// Inverse Initial Permutation Table
int[] IP1 = { 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 };
// first key-hePermutation Table
int[] PC1 = { 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 };
// second key-Permutation Table
int[] PC2 = { 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 };
// Expansion D-box Table
int[] EP = { 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 };
// Straight Permutation Table
int[] P = { 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 };
// S-box Table
int[][][] sbox = {
{ { 14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7 },
{ 0, 15, 7, 4, 14, 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 },
{ 13, 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[] shiftBits = { 1, 1, 2, 2, 2, 2, 2, 2,
1, 2, 2, 2, 2, 2, 2, 1 };
// hexadecimal to binary conversion
String hextoBin(String input)
{
int n = input.length() * 4;
input = Long.toBinaryString(
Long.parseUnsignedLong(input, 16));
while (input.length() < n)
input = "0" + input;
return input;
}
// binary to hexadecimal conversion
String binToHex(String input)
{
int n = (int)input.length() / 4;
input = Long.toHexString(
Long.parseUnsignedLong(input, 2));
while (input.length() < n)
input = "0" + input;
return input;
}
// per-mutate input hexadecimal
// according to specified sequence
String permutation(int[] sequence, String input)
{
String output = "";
input = hextoBin(input);
for (int i = 0; i < sequence.length; i++)
output += input.charAt(sequence[i] - 1);
output = binToHex(output);
return output;
}
// xor 2 hexadecimal strings
String xor(String a, String b)
{
// hexadecimal to decimal(base 10)
long t_a = Long.parseUnsignedLong(a, 16);
// hexadecimal to decimal(base 10)
long t_b = Long.parseUnsignedLong(b, 16);
// xor
t_a = t_a ^ t_b;
// decimal to hexadecimal
a = Long.toHexString(t_a);
// prepend 0's to maintain length
while (a.length() < b.length())
a = "0" + a;
return a;
}
// left Circular Shifting bits
String leftCircularShift(String input, int numBits)
{
int n = input.length() * 4;
int perm[] = new int[n];
for (int i = 0; i < n - 1; i++)
perm[i] = (i + 2);
perm[n - 1] = 1;
while (numBits-- > 0)
input = permutation(perm, input);
return input;
}
// preparing 16 keys for 16 rounds
String[] getKeys(String key)
{
String keys[] = new String[16];
// first key permutation
key = permutation(PC1, key);
for (int i = 0; i < 16; i++) {
key = leftCircularShift(
key.substring(0, 7), shiftBits[i])
+ leftCircularShift(key.substring(7, 14),
shiftBits[i]);
// second key permutation
keys[i] = permutation(PC2, key);
}
return keys;
}
// s-box lookup
String sBox(String input)
{
String output = "";
input = hextoBin(input);
for (int i = 0; i < 48; i += 6) {
String temp = input.substring(i, i + 6);
int num = i / 6;
int row = Integer.parseInt(
temp.charAt(0) + "" + temp.charAt(5), 2);
int col = Integer.parseInt(
temp.substring(1, 5), 2);
output += Integer.toHexString(
sbox[num][row][col]);
}
return output;
}
String round(String input, String key, int num)
{
// fk
String left = input.substring(0, 8);
String temp = input.substring(8, 16);
String right = temp;
// Expansion permutation
temp = permutation(EP, temp);
// xor temp and round key
temp = xor(temp, key);
// lookup in s-box table
temp = sBox(temp);
// Straight D-box
temp = permutation(P, temp);
// xor
left = xor(left, temp);
System.out.println("Round "
+ (num + 1) + " "
+ right.toUpperCase()
+ " " + left.toUpperCase() + " "
+ key.toUpperCase());
// swapper
return right + left;
}
String encrypt(String plainText, String key)
{
int i;
// get round keys
String keys[] = getKeys(key);
// initial permutation
plainText = permutation(IP, plainText);
System.out.println(
"After initial permutation: "
+ plainText.toUpperCase());
System.out.println(
"After splitting: L0="
+ plainText.substring(0, 8).toUpperCase()
+ " R0="
+ plainText.substring(8, 16).toUpperCase() + "\n");
// 16 rounds
for (i = 0; i < 16; i++) {
plainText = round(plainText, keys[i], i);
}
// 32-bit swap
plainText = plainText.substring(8, 16)
+ plainText.substring(0, 8);
// final permutation
plainText = permutation(IP1, plainText);
return plainText;
}
String decrypt(String plainText, String key)
{
int i;
// get round keys
String keys[] = getKeys(key);
// initial permutation
plainText = permutation(IP, plainText);
System.out.println(
"After initial permutation: "
+ plainText.toUpperCase());
System.out.println(
"After splitting: L0="
+ plainText.substring(0, 8).toUpperCase()
+ " R0=" + plainText.substring(8, 16).toUpperCase()
+ "\n");
// 16-rounds
for (i = 15; i > -1; i--) {
plainText = round(plainText, keys[i], 15 - i);
}
// 32-bit swap
plainText = plainText.substring(8, 16)
+ plainText.substring(0, 8);
plainText = permutation(IP1, plainText);
return plainText;
}
}
public static void main(String args[])
{
String text = "123456ABCD132536";
String key = "AABB09182736CCDD";
DES cipher = new DES();
System.out.println("Encryption:\n");
text = cipher.encrypt(text, key);
System.out.println(
"\nCipher Text: " + text.toUpperCase() + "\n");
System.out.println("Decryption\n");
text = cipher.decrypt(text, key);
System.out.println(
"\nPlain Text: "
+ text.toUpperCase());
}
}
// code contributed by Abhay BhatPython
# Hexadecimal to binary conversion
def hex2bin(s):
mp = {'0' : "0000",
'1' : "0001",
'2' : "0010",
'3' : "0011",
'4' : "0100",
'5' : "0101",
'6' : "0110",
'7' : "0111",
'8' : "1000",
'9' : "1001",
'A' : "1010",
'B' : "1011",
'C' : "1100",
'D' : "1101",
'E' : "1110",
'F' : "1111" }
bin = ""
for i in range(len(s)):
bin = bin + mp[s[i]]
return bin
# Binary to hexadecimal conversion
def bin2hex(s):
mp = {"0000" : '0',
"0001" : '1',
"0010" : '2',
"0011" : '3',
"0100" : '4',
"0101" : '5',
"0110" : '6',
"0111" : '7',
"1000" : '8',
"1001" : '9',
"1010" : 'A',
"1011" : 'B',
"1100" : 'C',
"1101" : 'D',
"1110" : 'E',
"1111" : 'F' }
hex = ""
for i in range(0,len(s),4):
ch = ""
ch = ch + s[i]
ch = ch + s[i + 1]
ch = ch + s[i + 2]
ch = ch + s[i + 3]
hex = hex + mp[ch]
return hex
# Binary to decimal conversion
def bin2dec(binary):
binary1 = binary
decimal, i, n = 0, 0, 0
while(binary != 0):
dec = binary % 10
decimal = decimal + dec * pow(2, i)
binary = binary//10
i += 1
return decimal
# Decimal to binary conversion
def dec2bin(num):
res = bin(num).replace("0b", "")
if(len(res)%4 != 0):
div = len(res) / 4
div = int(div)
counter =(4 * (div + 1)) - len(res)
for i in range(0, counter):
res = '0' + res
return res
# Permute function to rearrange the bits
def permute(k, arr, n):
permutation = ""
for i in range(0, n):
permutation = permutation + k[arr[i] - 1]
return permutation
# shifting the bits towards left by nth shifts
def shift_left(k, nth_shifts):
s = ""
for i in range(nth_shifts):
for j in range(1,len(k)):
s = s + k[j]
s = s + k[0]
k = s
s = ""
return k
# calculating xow of two strings of binary number a and b
def xor(a, b):
ans = ""
for i in range(len(a)):
if a[i] == b[i]:
ans = ans + "0"
else:
ans = ans + "1"
return ans
# Table of Position of 64 bits at initial level: Initial Permutation Table
initial_perm = [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]
# Expansion D-box Table
exp_d = [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 ]
# Straight Permutaion Table
per = [ 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 ]
# S-box Table
sbox = [[[14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7],
[ 0, 15, 7, 4, 14, 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],
[13, 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] ] ]
# Final Permutaion Table
final_perm = [ 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 ]
def encrypt(pt, rkb, rk):
pt = hex2bin(pt)
# Initial Permutation
pt = permute(pt, initial_perm, 64)
print("After initial permutation", bin2hex(pt))
# Splitting
left = pt[0:32]
right = pt[32:64]
for i in range(0, 16):
# Expansion D-box: Expanding the 32 bits data into 48 bits
right_expanded = permute(right, exp_d, 48)
# XOR RoundKey[i] and right_expanded
xor_x = xor(right_expanded, rkb[i])
# S-boxex: substituting the value from s-box table by calculating row and column
sbox_str = ""
for j in range(0, 8):
row = bin2dec(int(xor_x[j * 6] + xor_x[j * 6 + 5]))
col = bin2dec(int(xor_x[j * 6 + 1] + xor_x[j * 6 + 2] + xor_x[j * 6 + 3] + xor_x[j * 6 + 4]))
val = sbox[j][row][col]
sbox_str = sbox_str + dec2bin(val)
# Straight D-box: After substituting rearranging the bits
sbox_str = permute(sbox_str, per, 32)
# XOR left and sbox_str
result = xor(left, sbox_str)
left = result
# Swapper
if(i != 15):
left, right = right, left
print("Round ", i + 1, " ", bin2hex(left), " ", bin2hex(right), " ", rk[i])
# Combination
combine = left + right
# Final permutaion: final rearranging of bits to get cipher text
cipher_text = permute(combine, final_perm, 64)
return cipher_text
pt = "123456ABCD132536"
key = "AABB09182736CCDD"
# Key generation
# --hex to binary
key = hex2bin(key)
# --parity bit drop table
keyp = [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 ]
# getting 56 bit key from 64 bit using the parity bits
key = permute(key, keyp, 56)
# Number of bit shifts
shift_table = [1, 1, 2, 2,
2, 2, 2, 2,
1, 2, 2, 2,
2, 2, 2, 1 ]
# Key- Compression Table : Compression of key from 56 bits to 48 bits
key_comp = [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 ]
# Splitting
left = key[0:28] # rkb for RoundKeys in binary
right = key[28:56] # rk for RoundKeys in hexadecimal
rkb = []
rk = []
for i in range(0, 16):
# Shifting the bits by nth shifts by checking from shift table
left = shift_left(left, shift_table[i])
right = shift_left(right, shift_table[i])
# Combination of left and right string
combine_str = left + right
# Compression of key from 56 to 48 bits
round_key = permute(combine_str, key_comp, 48)
rkb.append(round_key)
rk.append(bin2hex(round_key))
print("Encryption")
cipher_text = bin2hex(encrypt(pt, rkb, rk))
print("Cipher Text : ",cipher_text)
print("Decryption")
rkb_rev = rkb[::-1]
rk_rev = rk[::-1]
text = bin2hex(encrypt(cipher_text, rkb_rev, rk_rev))
print("Plain Text : ",text)
# This code is contributed by Aditya Jain输出：
Encryption:
After initial permutation: 14A7D67818CA18AD
After splitting: L0=14A7D678 R0=18CA18AD
Round 1 18CA18AD 5A78E394 194CD072DE8C
Round 2 5A78E394 4A1210F6 4568581ABCCE
Round 3 4A1210F6 B8089591 06EDA4ACF5B5
Round 4 B8089591 236779C2 DA2D032B6EE3
Round 5 236779C2 A15A4B87 69A629FEC913
Round 6 A15A4B87 2E8F9C65 C1948E87475E
Round 7 2E8F9C65 A9FC20A3 708AD2DDB3C0
Round 8 A9FC20A3 308BEE97 34F822F0C66D
Round 9 308BEE97 10AF9D37 84BB4473DCCC
Round 10 10AF9D37 6CA6CB20 02765708B5BF
Round 11 6CA6CB20 FF3C485F 6D5560AF7CA5
Round 12 FF3C485F 22A5963B C2C1E96A4BF3
Round 13 22A5963B 387CCDAA 99C31397C91F
Round 14 387CCDAA BD2DD2AB 251B8BC717D0
Round 15 BD2DD2AB CF26B472 3330C5D9A36D
Round 16 19BA9212 CF26B472 181C5D75C66D
Cipher Text: C0B7A8D05F3A829C
Decryption
After initial permutation: 19BA9212CF26B472
After splitting: L0=19BA9212 R0=CF26B472
Round 1 CF26B472 BD2DD2AB 181C5D75C66D
Round 2 BD2DD2AB 387CCDAA 3330C5D9A36D
Round 3 387CCDAA 22A5963B 251B8BC717D0
Round 4 22A5963B FF3C485F 99C31397C91F
Round 5 FF3C485F 6CA6CB20 C2C1E96A4BF3
Round 6 6CA6CB20 10AF9D37 6D5560AF7CA5
Round 7 10AF9D37 308BEE97 02765708B5BF
Round 8 308BEE97 A9FC20A3 84BB4473DCCC
Round 9 A9FC20A3 2E8F9C65 34F822F0C66D
Round 10 2E8F9C65 A15A4B87 708AD2DDB3C0
Round 11 A15A4B87 236779C2 C1948E87475E
Round 12 236779C2 B8089591 69A629FEC913
Round 13 B8089591 4A1210F6 DA2D032B6EE3
Round 14 4A1210F6 5A78E394 06EDA4ACF5B5
Round 15 5A78E394 18CA18AD 4568581ABCCE
Round 16 14A7D678 18CA18AD 194CD072DE8C
Plain Text: 123456ABCD132536请参阅 – AES 和 DES 密码之间的区别