/*
* Encrypt a plaintext message using the mt19937 generator as keystream
*/
size_t encrypt( uint8_t *ctext[], const uint8_t ptext[], const size_t len)
{
size_t i;
uint8_t *keystream;
if (!random_prefix_len)
random_prefix_len = 1 + (get_random_value() % 15);
// Init MT19937 prng to a new seed
password_token_reset();
keystream = malloc(len*sizeof(uint8_t));
if (NULL == keystream)
return 0x00;
*ctext = malloc((random_prefix_len + len)*sizeof(uint8_t));
if (NULL == *ctext)
{
free(keystream);
return 0x00;
}
for (i = 0; i < random_prefix_len; i++)
(*ctext)[i] = (uint8_t) get_random_value();
mt19937_init( &cipher_mt, cipher_mt.seed);
for (i = 0; i < len; i++)
keystream[i] = mt19937_get_value(&cipher_mt);
xor_encode(&((*ctext)[random_prefix_len]), ptext, len, keystream, len);
free(keystream);
return random_prefix_len + len;
}
/*
* Decrypt a ciphertext message using the mt19937 generator as keystream
*/
unsigned int decrypt( uint8_t *ptext[], const uint8_t ctext[], const size_t len)
{
size_t i;
uint8_t *keystream;
// MT PRNG not init
if (!token_init)
return 0x01;
keystream = malloc(len*sizeof(uint8_t));
if (NULL == keystream)
return 0x01;
*ptext = malloc((len - random_prefix_len)*sizeof(uint8_t));
if (NULL == ptext)
{
free(keystream);
return 0x01;
}
mt19937_init( &cipher_mt, cipher_mt.seed);
for (i = 0; i < len; i++)
keystream[i] = mt19937_get_value(&cipher_mt);
xor_encode(*ptext , ctext + random_prefix_len, len, keystream, len);
free(keystream);
return 0x00;
}
int main(int argc, char *argv[])
{
clock_t start, finish;
FILE *in, *out;
if (argc != 4) {
fprintf(stderr,
"Usage: xe <key> <input file name> <output file name>\n");
return EXIT_FAILURE;
}
in = fopen(argv[2], "rb");
out = fopen(argv[3], "wb");
if (in == NULL || out == NULL) {
if (in != NULL)
fclose(in);
if (out != NULL) {
fclose(out);
remove(argv[3]);
}
fprintf(stderr, "One or more files can't be opened.\n");
return EXIT_FAILURE;
}
fprintf(stderr, "Encrypting...\t");
start = clock();
if (!xor_encode(atoi(argv[1]), in, out)) {
perror("Unexpected error occured.\n" \
"Details of the last error (if any)");
return errno;
}
finish = clock();
fprintf(stderr, "done! (%g seconds)\n",
(float)(finish - start) / CLOCKS_PER_SEC);
return EXIT_SUCCESS;
}
