#include "../lib/lib.h"
#include "../lib/lib2.h"
#include "../lib/lib3.h"
#include "../lib/lib4.h"
#include <time.h>

/**
  * Assume same key AND same nonce, this leads to the same keystream
  * every time. Than it is easy to discover the keystream with the edit
  * function. Simple XOR cihertext agianst out inserted text.
  *
  * If the nonce change for each edit call, the above won't work. We have for
  * every edit a new keystream, that makes it harder. 
  * 
  *
  **/

int main()
{
	generate_random_bytes(key, 16);
	generate_random_bytes(nonce, 16);

	char *file_content;
	int file_length = read_base64_file("25.txt", &file_content);
	char *base64_decoded = malloc(file_length);
	
	int base64_decoded_length = decode_base64(file_content, base64_decoded);
	// the file ist AES-ECB encrypted
	char *plain_tmp = malloc(base64_decoded_length);
	aes_ecb(base64_decoded, base64_decoded_length, plain_tmp, "YELLOW SUBMARINE",
			16, 0);
	char *ciphertext = malloc(base64_decoded_length);

	aes_ctr(plain_tmp, base64_decoded_length, ciphertext, key, nonce);

	// start the attack
	// recover 4-byte-keystream in each iteration
	char *org_ciphertext = malloc(base64_decoded_length);
	memcpy(org_ciphertext, ciphertext, base64_decoded_length);
	int i, j;
	char keystream[16];
	char *plaintext = malloc(base64_decoded_length);
	char newtext[16] = "ABABABABABABABAB";
	for(i=0;i<(base64_decoded_length/16);i++) {
		aes_ctr_edit(ciphertext, base64_decoded_length, (i*16), newtext);
		for(j=0;j<16;j++) {
			keystream[j] = newtext[j] ^ ciphertext[i*16+j];
			plaintext[i*16+j] = keystream[j] ^ org_ciphertext[i*16+j];
		}
	}

	printf("Recovered plaintext: %s\n", plaintext);
}