Simple XOR encryption program for Capsaicin Kaiten Variant

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

char *xor(char *string, char *key) {
    int i;
    int n = strlen(string);
    for( i = 0 ; i < n ; i++) {
        if(string[i] != key[i]) {
            string[i] = string[i] ^ key[i];
        }
    }
    return string;
}

int print_string_literal(char *s) {
    putchar('\"');

    while (*s) {
        unsigned cp = (unsigned char)*s++;
        printf("\\x%.2x", cp);
    }

    putchar('\"');
}

int main(int argc, char **argv[]) {
    if(argc < 3) {
        printf("Usage : %s <key> <string>\n", argv[0]);
        exit(1);
    }
    char *key = argv[1];
    char *string = argv[2];
    printf("Key: \"%s\"\n", key);
    printf("Original: \"%s\"\n", string);
    printf("Original (Hex): ");
    print_string_literal(string);
    printf("\n");
    printf("Encrypted: ");
    print_string_literal(xor(string, key));
    printf("\n");
    return 0;
}