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/* Public key cracker.
*
* Can be used to find public keys starting with specific hex (ABCD) for example.
*
* NOTE: There's probably a way to make this faster.
*
* Usage: ./cracker ABCDEF
*
* Will try to find a public key starting with: ABCDEF
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sodium.h>
#include "../../toxcore/ccompat.h"
// Secret key and public key length
#define KEY_LEN 32
static void print_key(const uint8_t *client_id)
{
for (int j = 0; j < KEY_LEN; ++j) {
printf("%02X", client_id[j]);
}
}
int main(int argc, char *argv[])
{
if (argc < 2) {
printf("usage: ./cracker public_key(or beginning of one in hex format)\n");
return 0;
}
long long unsigned int num_tries = 0;
size_t len = strlen(argv[1]) / 2;
unsigned char *key = (unsigned char *)malloc(len);
const char *hex_end = nullptr;
if (sodium_hex2bin(key, len, argv[1], strlen(argv[1]), nullptr, nullptr, &hex_end) != 0
|| hex_end != argv[1] + strlen(argv[1])) {
printf("Invalid key provided\n");
return 1;
}
uint8_t pub_key[KEY_LEN], priv_key[KEY_LEN], c_key[KEY_LEN];
if (len > KEY_LEN) {
printf("%zu characters given, truncating to: %d\n", len * 2, KEY_LEN * 2);
len = KEY_LEN;
}
memcpy(c_key, key, len);
free(key);
randombytes(priv_key, KEY_LEN);
while (1) {
crypto_scalarmult_curve25519_base(pub_key, priv_key);
if (memcmp(c_key, pub_key, len) == 0) {
break;
}
/*
* We can't use the first and last bytes because they are masked in
* curve25519. Using them would generate duplicate keys.
*/
for (int i = (KEY_LEN - 1); i > 1; --i) {
priv_key[i - 1] += 1;
if (priv_key[i - 1] != 0) {
break;
}
}
++num_tries;
}
printf("Public key:\n");
print_key(pub_key);
printf("\nPrivate key:\n");
print_key(priv_key);
printf("\n %llu keys tried\n", num_tries);
return 0;
}
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