Added entry to TODO and a public key cracker (vanity key finder) to other/fun.

docs/TODO

@@ -28,6 +28,7 @@ Lossless UDP:
 
 Friend_requests.c:
     [NOT STARTED] What happens when a friend request is recieved needs to be changed.
+    [NOT STARTED] Add multiple nospam functionality.
 
 [DONE] File transfers
 [NOT STARTED] Offline messaging

other/fun/cracker.c

@@ -0,0 +1,75 @@
+/* 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 "../../testing/misc_tools.c"
+#include <time.h>
+
+/* NaCl includes*/
+#include <crypto_scalarmult_curve25519.h>
+#include <randombytes.h>
+
+/* Sodium include*/
+//#include <libsodium.h>
+
+void print_key(uint8_t *client_id)
+{
+    uint32_t j;
+
+    for (j = 0; j < 32; j++) {
+        printf("%02hhX", client_id[j]);
+    }
+}
+
+
+int main(int argc, char *argv[])
+{
+    if (argc < 2) {
+        printf("usage: ./cracker public_key(or beggining of one in hex format)\n");
+        return 0;
+    }
+
+    long long unsigned int num_tries = 0;
+
+    uint32_t len = strlen(argv[1]) / 2;
+    unsigned char *key = hex_string_to_bin(argv[1]);
+    uint8_t pub_key[32], priv_key[32], c_key[32];
+
+    if (len > 32)
+        len = 32;
+
+    memcpy(c_key, key, len);
+    free(key);
+    randombytes(priv_key, 32);
+
+    while (1) {
+        crypto_scalarmult_curve25519_base(pub_key, priv_key);
+        uint32_t i;
+
+        if (memcmp(c_key, pub_key, len) == 0)
+            break;
+
+        for (i = 32; i != 0; --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;
+}