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/* strkey -- String in Public Key
*
* Generates Tox's key pairs, checking if a certain string is in the public key.
*
* Requires sodium or nacl library.
*
* There seem to be some problems with the code working on Windows -- it works
* when built in debug mode with MinGW 4.8, but it doesn't work correctly when
* built in release.
*
* Usage: strkey <offset> <string>
*
* Offset - an integer specifying exact byte offset position of the string you
* are looking for within a public key. When offset is negative, the program
* just looks for the desired string being somewhere, doesn't matter where, in
* the public key.
*
* String - a hex string that you want to have in your public key. It must have
* an even number of letters, since every two hexes map to a single byte of
* the public key.
*
* Examples:
* strkey 0 0123
* Looks for a public key that begins with "0123".
*
* strkey 1 0123
* Looks for a public key that has "0123" starting at its second byte, i.e. "XX0123...".
*
* strkey 2 0123
* Looks for a public key that has "0123" starting at its third byte, i.e. "XXXX0123...".
* (each two hexes represent a single byte of a public key)
*
* strkey -1 AF57CC
* Looks for a public key that contains "AF57CC", regardless of its position.
*
* To compile with gcc and sodium: gcc strkey.c -o strkey -lsodium
*/
#include <stdio.h>
#include <string.h>
#include <sodium.h>
#define PRINT_TRIES_COUNT
static void print_key(unsigned char *key)
{
size_t i;
for (i = 0; i < crypto_box_PUBLICKEYBYTES; i++) {
if (key[i] < 16) {
fprintf(stdout, "0");
}
fprintf(stdout, "%hhX", key[i]);
}
}
int main(int argc, char *argv[])
{
unsigned char public_key[crypto_box_PUBLICKEYBYTES]; // null terminator
unsigned char secret_key[crypto_box_SECRETKEYBYTES];
int offset = 0;
size_t len;
unsigned char desired_bin[crypto_box_PUBLICKEYBYTES]; // null terminator
if (argc == 3) {
offset = atoi(argv[1]);
char *desired_hex = argv[2];
len = strlen(desired_hex);
if (len % 2 != 0) {
fprintf(stderr, "Desired key should have an even number of letters\n");
exit(1);
}
size_t block_length = (offset < 0 ? 0 : offset) + len / 2;
if (block_length > crypto_box_PUBLICKEYBYTES) {
fprintf(stderr, "The given key with the given offset exceed public key's length\n");
exit(1);
}
// convert hex to bin
char *pos = desired_hex;
size_t i;
for (i = 0; i < len; pos += 2) {
unsigned int value;
sscanf(pos, "%02x", &value);
desired_bin[i] = value;
++i;
}
} else {
fprintf(stdout, "Usage: executable <byte offset> <desired hex string with even number of letters>\n");
exit(1);
}
len /= 2;
#ifdef PRINT_TRIES_COUNT
long long unsigned int tries = 0;
#endif
if (offset < 0) {
int found = 0;
do {
#ifdef PRINT_TRIES_COUNT
tries ++;
#endif
crypto_box_keypair(public_key, secret_key);
int i;
for (i = 0; i <= crypto_box_PUBLICKEYBYTES - len; i ++) {
if (memcmp(public_key + i, desired_bin, len) == 0) {
found = 1;
break;
}
}
} while (!found);
} else {
unsigned char *p = public_key + offset;
do {
#ifdef PRINT_TRIES_COUNT
tries ++;
#endif
crypto_box_keypair(public_key, secret_key);
} while (memcmp(p, desired_bin, len) != 0);
}
fprintf(stdout, "Public key: ");
print_key(public_key);
fprintf(stdout, "\n");
fprintf(stdout, "Private key: ");
print_key(secret_key);
fprintf(stdout, "\n");
#ifdef PRINT_TRIES_COUNT
fprintf(stdout, "Found the key pair on %llu try.\n", tries);
#endif
return 0;
}
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