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文章目录
一、DES算法原理二、相关说明1.初始置换IP2.子密钥 Ki 的获取3.密码函数 f4.尾置换IP-1
三、DES算法具体实现(C++）
一、DES算法原理
DES算法是一种最通用的对称密钥算法，因为算法本身是公开的，所以其安全性在于密钥的安全性。基于密钥的算法通常有两类：对称算法和公开密钥算法。对称算法的对称性体现在加密密钥能够从解密密钥推算出来，反之亦然。在大多数对称算法中，加解密的密钥是相同的，DES就是这样。可见，对称密钥算法的加解密密钥都是保密的。而公开密钥算法的加密密钥是公开的，解密密钥是保密的。
二、相关说明
首先对输入明文转换后的0/1二进制字符串进行填充，确保我们处理的每个明文分组都是64位，在该函数中也把输入的密钥转换为了0/1字符串：
string chardeel(string& str1, string& str2) {
string temp_str = "";
int divi_times = (str1.size() % 8 ? str1.size() / 8 + 1 : str1.size() / 8); //计算分组个数
for (int i = 0; i
jude = true;
addchar = 8 - str1_temp.size() % 8;
}
int sub = str1_temp.size() * 8;
if (jude) {
for (int i = 0; i
for (int i = 0; i 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 };
/**
*密钥初始置换表
*/
int T2[8][7] = { 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,
3,55,47,39,31,23,15,
7,62,54,46,38,30,22,
14,6,61,53,45,37,29,
21,13,5,28,20,12,4 };
/**
*密钥循环左移位数表
*/
int T3[16] = { 1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1 };
/**
*密钥压缩置换表
*/
int T4[8][6] = { 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 };
/**
*数据扩展表
*/
int T5[8][6] = { 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盒置换表
*/
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}} };
/**
*P盒置换表
*/
int P[4][8] = { 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 };
/**
*最终置换表
*/
int T6[8][8] = { 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 };
/**
*最终置换函数 64位->64位
*函数说明：s为完成最后一轮循环得到的64为数据
*返回值为密文或明文
*/
string final_permutation(string s)
{
string rs = "";
for (int i = 0; i
rs += s[T6[i][j] - 1];
}
}
return rs;
}
/**
*P盒置换函数 32位->32位
*函数说明：s为S盒的输出
*/
string P_box(string s)
{
string rs = "";
for (int i = 0; i
rs += (s[P[i][j] - 1]);
}
}
return rs;
}
/**
*S盒置换函数 48位->32位
*函数说明：s为48位数据
*返回值为32位
*/
string S_box(string s)
{
string rs = "";
string s1;
int k1, k2;//S盒的行号和列号
int h = 1;//决定使用那个S盒
for (int i = 0; i
if (x
s1 += "1";
x = x % y;
y /= 2;
}
}
rs += s1;
}
return rs;
}
/**
*异或运算函数
*要求位数相同
*/
string desXOR(string s1, string s2)
{
string rs = "";
for (int i = 0; i
string rs = "";
for (int i = 0; i
rs += s[T5[i][j] - 1];
}
}
return rs;
}
/**
*密钥压缩置换函数 56位->48位
*函数说明：s为56为的密钥
*输出为48位的子密钥
*/
string secret_key_compression_replacement(string s)
{
string rs = "";
for (int i = 0; i
rs += s[T4[i][j] - 1];
}
}
return rs;
}
/**
*密钥循环左移函数 56位->56位
*函数说明：k为左移位数 s为密钥
*返回值位数不变
*/
string secret_ket_left_move(int k, string s)//密钥循环左移k位
{
string s1 = s.substr(0, 28);
string s2 = s.substr(28, 28);
string rs = s1.substr(k, 28 - k) + s1.substr(0, k) + s2.substr(k, 28 - k) + s2.substr(0, k);
return rs;
}
/**
*密钥初始置换函数 64位->56位
*函数说明：s为64位的初始密钥
*返回值为56位
*/
string secret_key_initial_permutation(string s)
{
string rs = "";
for (int i = 0; i
rs += s[T2[i][j] - 1];
}
}
return rs;
}
/**
*明文初始置换函数 64位->64位
*函数说明：s为初始明文 64位
*返回值为6位
*/
string plaintext_initial_permutation(string s)//明文初始置换
{
string rs = "";
for (int i = 0; i
rs += s[T1[i][j] - 1];
}
}
return rs;
}
/**
*16进制转2进制函数
*函数说明：s为16进制字符串
*返回为2进制字符串
*/
string des_H(string s)
{
string s1;
string rs = "";
for (int i = 0; i
x = s[i] - '0';
}
else
{
x = s[i] - 'A' + 10;
}
s1 = "";
int y = 8;
for (int j = 1; j
y /= 2;
s1 += "0";
}
else
{
s1 += "1";
x = x % y;
y = y / 2;
}
}
rs += s1;
}
return rs;
}
/**
*2进制转16进制函数
*str为2进制字符串
*返回值为16进制字符串
*/
string des_G(string str)
{
string rs = "";
char temp;
for (int i = 0; i
temp = (char)(x - 10 + 'A');
}
else
{
temp = (char)(x + '0');
}
rs += temp;
}
return rs;
}
/**
*封装函数f
*函数说明：接收32位数据和48位的子密钥 产生一个32位的输出
*str1:32位数据 str2:48位的子密钥
*返回值32位
*/
string des_f(string str1, string str2)
{
string expendR = plaintext_righthalf_extended_permutation(str1);
//cout
s = secret_ket_left_move(T3[i - 1], s);
desKeys[i] = secret_key_compression_replacement(s);
}
}
/*
* 明文字符串转换成0/1字符串
*/
string des_StrToBitStr(string str)
{
bitset bstr;
for (int i = 0; i
bstr[i * 8 + j] = bits[7 - j];
}
}
string s = bstr.to_string();
//添加一个翻转操作
reverse(begin(s), end(s));
return s;
}
/*
* 0/1字符串装换为字符形式的字符串
*/
string des_BitStrToStr(string bstr)
{
string str = "";
//每八位转化成十进制，然后将数字结果转化成字符
int sum;
for (int i = 0; i
string temp_str = "";
int divi_times = (str1.size() % 8 ? str1.size() / 8 + 1 : str1.size() / 8); //计算分组个数
for (int i = 0; i
jude = true;
addchar = 8 - str1_temp.size() % 8;
}
int sub = str1_temp.size() * 8;
if (jude) {
for (int i = 0; i
for (int i = 0; i
str1 = chardeel(str1, str2); //明文分组和填充，返回01字符串
des_generateKeys(str2); //生成16个子密钥
int divi_times = str1.size() / 64; //分成多少组去进行des
string rs_temp = "";
for (int i = 0; i
newleft = right;
right = desXOR(left, des_f(right, desKeys[i]));
left = newleft;
}
//第四步:合并数据 注意位R16L16
string rs = right + left;
//结尾置换
rs = final_permutation(rs);
rs_temp = rs_temp + rs;
}
return rs_temp;
}
/**
*解密函数
*str为密文
*输出明文
*/
string des_decrypt(string str)
{
int divi_times = str.size() / 64; //分成多少组去进行des
string rs_temp = "";
for (int i = 0; i
newleft = right;
right = desXOR(left, des_f(right, desKeys[i]));
left = newleft;
}
//合并
string rs = right + left;
//最后置换
rs = final_permutation(rs);
rs_temp = rs_temp + rs;
}
rs_temp = des_BitStrToStr(rs_temp);
return rs_temp;
}
int main()
{
/*string str1 = "abc";
cout |