xor.c

/*
Author: chankruze ([email protected])
Created: Wed Mar 09 2022 10:06:36 GMT+0530 (India Standard Time)

Copyright (c) geekofia 2022 and beyond
*/

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

#define MAX_TEXT_LEN 100
#define MAX_KEY_LEN 10
// #define printld(x) printf("%ld\n", x)
// #define printd(x) printf("%d\n", x)
// #define what_char(x) printf("c = %c, ord(c) = %d\n", x, ord(x))

int ord(char c) {
    return c;
}

char chr(int x) {
    return x;
}

char* encrypt(char* plain_text, char* xor_key) {
    // length of plain text
    size_t len_plain_text = strlen(plain_text);
    // length of key
    size_t len_xor_key = strlen(xor_key);
    // empty character array of encrypted text
    char* encrypted = malloc(len_plain_text);

    // loop over each character in plain text
    for (size_t i = 0; i < len_plain_text; i++) {
        // xor each character's int with key's correspondence character's int
        char x = chr(ord(plain_text[i]) ^ ord(xor_key[i % len_xor_key]));
        // what_char(x);
        encrypted[i] = x;
    }

    return encrypted;
}

char* decrypt(char* cipher_text, char* xor_key) {
    // length of cipher text
    size_t len_cipher_text = strlen(cipher_text);
    // length of key
    size_t len_xor_key = strlen(xor_key);
    // empty character array of cipher text
    char* decrypted = malloc(len_cipher_text);

    // loop over each character in cipher text
    for (size_t i = 0; i < len_cipher_text; i++) {
        // xor each character's int with key's correspondence character's int
        char x = chr(ord(cipher_text[i]) ^ ord(xor_key[i % len_xor_key]));
        // what_char(x);
        decrypted[i] = x;
    }

    return decrypted;
}

int main() {
    // plain text user input
    char plain_text[MAX_TEXT_LEN];
    scanf("%s", plain_text);

    // xor key
    char xor_key[MAX_KEY_LEN];
    scanf("%s", xor_key);

    char* encrypted = encrypt(plain_text, xor_key);
    char* decrypted = decrypt(encrypted, xor_key);

    // ui
    printf("original = %s\n", plain_text);
    printf("encrypted = %s\n", encrypted);
    printf("decrypted = %s\n", decrypted);

    // cleanup
    free(encrypted);
    free(decrypted);
}