Example: XOR Cipher Encryption and Decryption in C

// XOR Cipher Encryption and Decryption
#include <stdio.h>
#include <string.h>

// Function to encrypt/decrypt a message using XOR cipher
void xorCipher(char text[], char key_char) {
    int i;
    for (i = 0; text[i] != '\0'; ++i) {
        text[i] = text[i] ^ key_char; // XOR each character with the key
    }
}

int main() {
    // Step 1: Declare variables for message and key
    char message[100];
    char key_char; // Single character key for simplicity

    printf("Enter a message to encrypt: ");
    fgets(message, sizeof(message), stdin);
    message[strcspn(message, "\n")] = 0; // Remove trailing newline

    printf("Enter a single character key: ");
    scanf(" %c", &key_char); // Note the space before %c to consume newline

    // Step 2: Encrypt the message
    char encryptedMessage[100];
    strcpy(encryptedMessage, message); // Copy original message
    xorCipher(encryptedMessage, key_char);
    printf("Encrypted message: %s\n", encryptedMessage);

    // Step 3: Decrypt the message (XOR is symmetric, same function)
    char decryptedMessage[100];
    strcpy(decryptedMessage, encryptedMessage); // Copy encrypted message
    xorCipher(decryptedMessage, key_char); // Apply XOR again
    printf("Decrypted message: %s\n", decryptedMessage);

    return 0;
}