vigenere密码算法c语言

以下是 Vigenere 密码算法的 C 语言实现代码示例：

#include <stdio.h>
#include <string.h>

void vigenere_encrypt(char plain_text[], char key[]) {
    int len_plain_text = strlen(plain_text);
    int len_key = strlen(key);

    for(int i = 0, j = 0; i < len_plain_text; i++, j++) {
        if(j >= len_key) {
            j = 0;
        }

        plain_text[i] = ((plain_text[i] + key[j]) % 26) + 'A';
    }
}

void vigenere_decrypt(char cipher_text[], char key[]) {
    int len_cipher_text = strlen(cipher_text);
    int len_key = strlen(key);

    for(int i = 0, j = 0; i < len_cipher_text; i++, j++) {
        if(j >= len_key) {
            j = 0;
        }

        cipher_text[i] = ((cipher_text[i] - key[j] + 26) % 26) + 'A';
    }
}

int main() {
    char plain_text[100];
    char key[100];
    char cipher_text[100];

    printf("Enter plain text: ");
    scanf("%s", plain_text);

    printf("Enter key: ");
    scanf("%s", key);

    // Encrypt the plain text
    vigenere_encrypt(plain_text, key);
    printf("Encrypted text: %s\n", plain_text);

    // Decrypt the cipher text
    vigenere_decrypt(plain_text, key);
    printf("Decrypted text: %s\n", plain_text);

    return 0;
}

注意：此代码只用于学习和理解 Vigenere 密码算法，不应用于实际安全需求。