置换密码原理：把明文中的字母重新排列，字母本身不变，但其位置改变了，这样编成的密码称为置换密码。置换密码又称为移位密码，因为对照明密文来看，字母的位置被移动了。
加密代码实现：
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#include <iostream> #include <string> #include <string.h> #include <unistd.h> using namespace std; struct group { char ch = '\0'; int num = -1; }; int Check(string s) { //检查输入的字符串是否为纯英文 int i = 0; while (s[i] != '\0') { if (!((s[i] >= 'a'&&s[i] <= 'z') || (s[i] >= 'A'&&s[i] <= 'Z'))) { cout << "Error!Please enter again!" << endl; return 1; } i++; } return 0; } //处理密钥,返回指针数组 int *wordKey(string key, int k[20]) { int i, j; // int k[20] = { 0 }; int *p = k; int flag = 0; char temp1; char tem[20] = { 0 }; char keygroup[20] = { 0 }; for (i = 0; i < key.length(); i++) {//设置临时数组 keygroup[i] = key[i]; } //冒泡排序 for (i = 0; i < key.length(); i++) { flag = 0; for (j = 0; j < key.length() - i - 1; j++) { if (keygroup[j] > keygroup[j + 1]) { temp1 = keygroup[j]; keygroup[j] = keygroup[j + 1]; keygroup[j + 1] = temp1; flag = 1; } } if (flag == 0) break; } //设置临时数组 for (i = 0; i < key.length(); i++) { tem[i] = keygroup[i]; } //对应的密钥顺序 cout << endl << "key = (d, f)" << endl; cout << "d = " << key.length() << " "; cout << "f = ("; for (i = 0; i < key.length(); i++) { for (j = 0; j < key.length(); j++) { if (keygroup[j] == key[i] && tem[j] != '#') { k[i] = j + 1; tem[j] = '#'; cout << " " << k[i]; break; } } } cout << " )" << endl << endl; return p; } int main(){ int flag = 0; int i, j, t; int k[20] = { 0 }; int *p; char tem[20] = { 0 }; char keygroup[20] = { 0 }; char plain[30] = { 0 }; char cipher[30] = { 0 }; string st, key; group list[10]; do { fflush(stdin); cout << "-------------Permutation cipher(Encryption)------------" << endl; cout << " the null letter is 'x' " << endl; cout << "Please enter the plaintext:"; cin >> st; flag = Check(st); } while (flag); do { //输入key fflush(stdin); cout << "Please enter the key: "; cin >> key; flag = Check(key); } while (flag); //明文不是key的整数倍补'x' t = st.length(); if (t%key.length() != 0) t = ((t / (key.length()) + 1)*key.length()); for (i = 0; i < t; i++) { if (i < st.length()) plain[i] = st[i]; else plain[i] = 'x'; } p = wordKey(key, k); //展示 cout << " "; for (i = 0; i < (strlen(plain) / key.length()); i++) { for (j = 0; j < key.length(); j++) { cout << p[j]; } cout << " "; } cout << endl; for (i = 0; i < strlen(plain); i++) { if ((i%key.length()) == 0) cout << " "; cout << plain[i]; } cout << endl << endl; //整理密文 for (i = 0; i < t / (key.length()); i++) { for (j = 0; j < key.length(); j++) { cipher[i*key.length() + p[j] - 1] = plain[i*key.length() + j]; } } //输出密文 cout << "CipherText:"; for (i = 0; i < strlen(cipher); i++) { cout << cipher[i]; } cout << endl << endl; return 0; } |
解密代码实现：
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#include <iostream> #include <string> #include <string.h> #include <unistd.h> using namespace std; struct group { char ch = '\0'; int num = -1; }; int Check(string s) { //检查输入的字符串是否为纯英文 int i = 0; while (s[i] != '\0') { if (!((s[i] >= 'a'&&s[i] <= 'z') || (s[i] >= 'A'&&s[i] <= 'Z'))) { cout << "Error!Please enter again!" << endl; return 1; } i++; } return 0; } //处理密钥,返回指针数组 int *wordKey(string key, int k[20]) { int i, j; // int k[20] = { 0 }; int *p = k; int flag = 0; char temp1; char tem[20] = { 0 }; char keygroup[20] = { 0 }; for (i = 0; i < key.length(); i++) {//设置临时数组 keygroup[i] = key[i]; } //冒泡排序 for (i = 0; i < key.length(); i++) { flag = 0; for (j = 0; j < key.length() - i - 1; j++) { if (keygroup[j] > keygroup[j + 1]) { temp1 = keygroup[j]; keygroup[j] = keygroup[j + 1]; keygroup[j + 1] = temp1; flag = 1; } } if (flag == 0) break; } //设置临时数组 for (i = 0; i < key.length(); i++) { tem[i] = keygroup[i]; } //对应的密钥顺序 cout << endl << "key = (d, f)" << endl; cout << "d = " << key.length() << " "; cout << "f = ("; for (i = 0; i < key.length(); i++) { for (j = 0; j < key.length(); j++) { if (keygroup[j] == key[i] && tem[j] != '#') { k[i] = j + 1; tem[j] = '#'; cout << " " << k[i]; break; } } } cout << " )" << endl << endl; return p; } int main(){ int flag = 0; int i, j; int k[20] = { 0 }; int *p; char tem[20] = { 0 }; char keygroup[20] = { 0 }; char plain[30] = { 0 }; char cipher[30] = { 0 }; string st, key; group list[10]; do { fflush(stdin); system("cls"); cout << "-------------Permutation cipher(Decryption)------------" << endl; cout << "Please enter the ciphertext:"; cin >> st; flag = Check(st); } while (flag); do { //输入key fflush(stdin); cout << "Please enter the key: "; cin >> key; flag = Check(key); } while (flag); if (((st.length()) % (key.length())) != 0) { cout << endl << "Error!The length of the ciphertext must be an integral multiple of the length of the key!" << endl << endl; exit(-1); } p = wordKey(key, k); //展示 cout << " "; for (i = 0; i < (st.length() / key.length()); i++) { for (j = 0; j < key.length(); j++) { cout << p[j]; } cout << " "; } cout << endl; for (i = 0; i < st.length(); i++) { if ((i%key.length()) == 0) cout << " "; cout << st[i]; } cout << endl << endl; cout << "PlainText:"; for (i = 0; i < (st.length() / key.length()); i++) { for (j = 0; j < key.length(); j++) { cout << st[(i*key.length() + p[j] - 1)]; } } cout << endl << endl; return 0; } |
（编译运行环境：g++ [Debian 7.3.0-19] 7.3.0）
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