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代码运行的编译器为CLion或者VS-Code，CMake最低版本要求3.17 代码实现的是一个简易的加密和解密系统，里面包含了移位密码和RC4两种算法。了解【RC4】 移位加解密算法运行描述： 加密：输入一串由小写字母组成的字符串作为明文，输入一个整数作为密码，结果产生一个由大写字母组成的密文 解密：输入待解密的密文，输入一个整数作为密码，结果产生一个由小写字母组成的解密后的明文 RC4加解密算法运行描述： 加密：输入一个整数N，代表你要输入的密钥长度，回车后在输入N个整数，中间用空格隔开，回车后输入待加密的明文，可输入出回车键（\n）之外的任何字符，结果产生的密文会保存在全局变量rc4_cipher中，解密时不需要输入密文。 解密：输入一个整数N，代表代表你要输入的密钥长度，回车后再输入N个整数，中间用空格隔开，结果产生明文 /* * author: surqing */ #include #include #include #define MSG_MAX_LENGTH 1001 // 输入明文的最大长度 #define TABLE_SIZE 256 // RC4加密的S表和K表的大小 unsigned char S[TABLE_SIZE]; unsigned char K[TABLE_SIZE]; unsigned char * rc4_cipher = NULL; void shift(); void shift_encryption(); void shift_decryption(); char* shift_encrypt(const char* msg, const int key); char* shift_decrypt(const char* cipher, const int key); void RC4(); void RC4_encryption(); void RC4_decryption(); void init_S(); void init_K(); int* input_key(int size); void swap(unsigned char * table, int i, int j); void permute_S(); unsigned char* RC4_encrypt(unsigned char * msg); void RC4() { int opt = -1; while (opt) { printf("\n=========================\n" "*** RC4 CIPHER SYSTEM ***\n" "=========================\n"); printf("Please select operation:\n" "1.Encryption.\n" "2.Decryption.\n" "0.Exit.\n"); scanf("%d", &opt); if (opt == 0) { break; } else if (opt == 1) { RC4_encryption(); } else if (opt == 2) { RC4_decryption(); } else { printf("Input error, enter again please!\n"); } } return; } void RC4_encryption() { unsigned char msg[MSG_MAX_LENGTH]; int key_size; int* keys = NULL; // unsigned char *cipher = NULL; printf("Please input length of the key:\n"); scanf("%d", &key_size); printf("Please enter an integer key separated by Spaces:\n"); keys = input_key(key_size); init_S(); init_K(keys, key_size); permute_S(); printf("Please enter the plaintext to be encrypted:\n"); // scanf("%s", msg); getchar(); gets(msg); // cipher = RC4_encrypt(msg); if (rc4_cipher != NULL) free(rc4_cipher); rc4_cipher = RC4_encrypt(msg); printf("Your cipher is:\n"); printf("%s\n", rc4_cipher); printf("========== encryption over! ==========\n\n"); // free(cipher); return; } void RC4_decryption() { if (rc4_cipher == NULL) { printf("rc4_cipher is null, perform encryption first!!!\n"); return; } unsigned char cipher[MSG_MAX_LENGTH]; int key_size; int* keys = NULL; unsigned char *msg = NULL; printf("Please input length of the key:\n"); scanf("%d", &key_size); printf("Please enter an integer key separated by Spaces:\n"); keys = input_key(key_size); init_S(); init_K(keys, key_size); permute_S(); // printf("Please enter the cipher to be decrypted:\n"); // scanf("%s", cipher); msg = RC4_encrypt(rc4_cipher);// RC4是对称加密，通过对密文加密就能得到明文 printf("Your message is:\n%s\n========== Decryption over! ==========\n", msg); free(keys); free(msg); return; } void shift() { int opt = -1; while (opt) { printf("===========================\n" "*** SHIFT CIPHER SYSTEM ***\n" "===========================\n"); printf("Please select operation:\n" "1.Encryption.\n" "2.Decryption.\n" "0.Exit.\n"); scanf("%d", &opt); if (opt == 0) { break; } else if (opt == 1) { shift_encryption(); } else if (opt == 2) { shift_decryption(); } else { printf("Input error, enter again please!\n"); } } return; } void shift_encryption() { char msg[MSG_MAX_LENGTH]; char *cipher; int key; printf("Please enter a string to encrypt:\n"); scanf("%s", msg); printf("Please enter an integer as key:\n"); scanf("%d", &key); cipher = shift_encrypt(msg, key); printf("Your cipher is:\n"); printf("%s\n", cipher); printf("========== encryption over! ==========\n\n"); free(cipher); return; } void shift_decryption() { char cipher[MSG_MAX_LENGTH]; char* msg = NULL; int key; printf("Please input cipher to decrypt:\n"); scanf("%s", cipher); printf("Please input integer as key:\n"); scanf("%d", &key); msg = shift_decrypt(cipher, key); printf("Message is:\n"); printf("%s\n========== Decryption over! ==========\n\n", msg); free(msg); return; } char* shift_encrypt(const char* msg, const int key) { int msgLen = strlen(msg); char* cipher = NULL; int i; cipher = (char*) calloc(msgLen + 1, sizeof(char)); for (i = 0; i < msgLen; i++) { cipher[i] = (msg[i] - 'a' + key % 26) % 26 + 'A'; } return cipher; } char* shift_decrypt(const char* cipher, int key) { int cipLen = strlen(cipher); char* msg = NULL; int i; msg = (char*) calloc(cipLen + 1, sizeof(char)); for (i = 0; i < cipLen; i++) { msg[i] = (cipher[i] - 'A' + 26 - key % 26) % 26 + 'a'; } return msg; } void init_S() { int i; for (i = 0; i < TABLE_SIZE; i++) { S[i] = (unsigned char)i; } return; } void init_K(int* seed_key, int seed_key_size) { int i; for (i = 0; i < TABLE_SIZE; i++) { K[i] = (unsigned char)seed_key[i % seed_key_size]; } return; } int* input_key(int size) { int* key_arr = NULL; int i = 0; key_arr = (int*)calloc(size, sizeof(int)); if (key_arr == NULL) { perror("calloc failed in function of input_key!"); exit(1); } while (i < size) { scanf("%d", key_arr + i); key_arr[i] = (abs(key_arr[i])) % TABLE_SIZE; i++; } return key_arr; } void swap(unsigned char* table, int i, int j) { unsigned char t = table[i]; table[i] = table[j]; table[j] = t; return; } void permute_S() { int i = 0; int j = 0; for (i = 0; i < TABLE_SIZE; i++) { j = (j + S[i] + K[i]) % TABLE_SIZE; swap(S, i, j); } return; } unsigned char* RC4_encrypt(unsigned char* msg) { int i = 0; int m = 0; int n = 0; unsigned char* cipher = NULL; int msg_len = strlen(msg); cipher = (unsigned char*)calloc(msg_len + 1, sizeof(unsigned char)); if (cipher == NULL) { perror("calloc failed in function of encrypt!"); exit(1); } for (i = 0; i < msg_len; i++) { m = (m + 1) % TABLE_SIZE; n = (n + S[m]) % TABLE_SIZE; swap(S, m, n); unsigned char t = (S[m] + S[n]) % TABLE_SIZE; unsigned char k = S[t]; cipher[i] = k ^ msg[i]; } return cipher; } int main() { int opt = -1; while (opt != 0) { printf("================================\n" "********** SYSTEM **********\n" "================================\n"); printf("Please select operation:\n" "1. Shift encryption/decryption.\n" "2. RC4 encryption/decryption.\n" "0. Exit system.\n"); scanf("%d",&opt); if (opt == 0) { break; } else if (opt == 1) { shift(); } else if (opt == 2) { RC4(); } else { printf("Input error, please enter again:\n"); } } free(rc4_cipher); return 0; } |
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