perf: improve speed of cracker.c

- more inteligent secret key generation
- use OpenMP for multithreading

CMakeLists.txt

@@ -532,6 +532,15 @@ if (BUILD_MISC_TESTS)
   add_executable(save-generator
     other/fun/save-generator.c)
   target_link_modules(save-generator toxcore misc_tools)
+
+  add_executable(cracker
+    other/fun/cracker.c)
+  target_link_modules(cracker ${LIBSODIUM_LIBRARIES})
+  find_package(OpenMP)
+  if(OpenMP_C_FOUND)
+      target_link_libraries(cracker OpenMP::OpenMP_C)
+  endif()
+
   add_executable(afl_toxsave
     testing/afl_toxsave.c)
   target_link_modules(afl_toxsave toxcore)

other/fun/cracker.c

@@ -9,26 +9,98 @@
  * Will try to find a public key starting with: ABCDEF
  */
 
+#include <inttypes.h>
+#include <stdbool.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <time.h>
 
 /* Sodium includes*/
 #include <sodium/crypto_scalarmult_curve25519.h>
 #include <sodium/randombytes.h>
 
-#include "../../testing/misc_tools.h"
-#include "../../toxcore/ccompat.h"
+#define KEY_LEN 32
 
-static void print_key(uint8_t *client_id)
-{
-    uint32_t j;
+#if defined(_OPENMP)
+#include <omp.h>
+#define NUM_THREADS() ((unsigned) omp_get_max_threads())
+#else
+#define NUM_THREADS() (1U)
+#endif
 
-    for (j = 0; j < 32; j++) {
+static void print_key(const uint8_t *client_id)
+{
+    for (uint32_t j = 0; j < 32; j++) {
         printf("%02X", client_id[j]);
     }
 }
 
+/// bytes needs to be at least (hex_len+1)/2 long
+static size_t hex_string_to_bin(const char *hex_string, size_t hex_len, uint8_t *bytes)
+{
+    size_t i;
+    const char *pos = hex_string;
+    // make even
+
+    for (i = 0; i < hex_len / 2; ++i, pos += 2) {
+        uint8_t val;
+
+        if (sscanf(pos, "%02hhx", &val) != 1) {
+            return 0;
+        }
+
+        bytes[i] = val;
+    }
+
+    if (i * 2 < hex_len) {
+        uint8_t val;
+
+        if (sscanf(pos, "%hhx", &val) != 1) {
+            return 0;
+        }
+
+        bytes[i] = (uint8_t)(val << 4);
+        ++i;
+    }
+
+    return i;
+}
+
+static size_t match_hex_prefix(const uint8_t *key, const uint8_t *prefix, size_t prefix_len)
+{
+    size_t same = 0;
+    uint8_t diff = 0;
+    size_t i;
+
+    for (i = 0; i < prefix_len / 2; i++) {
+        diff = key[i] ^ prefix[i];
+
+        // First check high nibble
+        if ((diff & 0xF0) == 0) {
+            same++;
+        }
+
+        // Then low nibble
+        if (diff == 0) {
+            same++;
+        } else {
+            break;
+        }
+    }
+
+    // check last high nibble
+    if ((prefix_len % 2) && diff == 0) {
+        diff = key[i] ^ prefix[i];
+
+        // First check high nibble
+        if ((diff & 0xF0) == 0) {
+            same++;
+        }
+    }
+
+    return same;
+}
 
 int main(int argc, char *argv[])
 {
@@ -37,43 +109,126 @@ int main(int argc, char *argv[])
         return 0;
     }
 
-    long long unsigned int num_tries = 0;
+    size_t prefix_chars_len = strlen(argv[1]);
+
+    /*
+     * If you can afford the hardware to crack longer prefixes, you can probably
+     * afford to rewrite this program.
+     */
+    if (strlen(argv[1]) > 16) {
+        printf("Finding a key with more than 16 hex chars as prefix is not supported\n");
+        return -1;
+    }
 
-    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];
+    uint8_t hex_prefix[8] = {0};
 
-    if (len > 32) {
-        len = 32;
+    size_t prefix_len = hex_string_to_bin(argv[1], prefix_chars_len, hex_prefix);
+
+    if (prefix_len == 0) {
+        printf("Invalid hex key specified\n");
+        return -1;
     }
 
-    memcpy(c_key, key, len);
-    free(key);
-    randombytes(priv_key, 32);
+    printf("Searching for key with prefix: %s\n", argv[1]);
 
-    while (1) {
-        crypto_scalarmult_curve25519_base(pub_key, priv_key);
-        uint32_t i;
+    time_t start_time = time(NULL);
+    uint8_t pub_key[KEY_LEN];
+    uint64_t priv_key_shadow[KEY_LEN / 8];
+    uint8_t *priv_key = (uint8_t *) priv_key_shadow;
+    randombytes(priv_key, 32);
 
-        if (memcmp(c_key, pub_key, len) == 0) {
-            break;
+    /*
+     * We can't use the first and last bytes because they are masked in
+     * curve25519. Offset by 16 bytes to get better alignment.
+     */
+    uint64_t *counter = priv_key_shadow + 2;
+
+    // Can't check this case inside the loop because of uint64_t overflow
+    *counter += UINT64_MAX;
+
+    uint32_t longest_match = 0;
+
+    /* Maybe we're lucky */
+    crypto_scalarmult_curve25519_base(pub_key, priv_key);
+    uint32_t matching = (uint32_t) match_hex_prefix(pub_key, hex_prefix, prefix_chars_len);
+
+    if (matching > 0) {
+        longest_match = matching;
+        printf("Longest match after ~1 tries\n");
+        printf("Public key: ");
+        print_key(pub_key);
+        printf("\nSecret key: ");
+        print_key(priv_key);
+        printf("\n");
+
+        if (longest_match >= prefix_chars_len) {
+            printf("Found matching prefix, exiting...\n");
+            return 0;
         }
+    }
+
+    // Finishes a batch every ~10s on my PC
+    uint64_t batch_size = (UINT64_C(1) << 17) * NUM_THREADS();
 
-        for (i = 32; i != 0; --i) {
-            priv_key[i - 1] += 1;
+    double seconds_passed = 0.0;
+    double old_seconds_passed = seconds_passed;
 
-            if (priv_key[i - 1] != 0) {
-                break;
+    for (uint64_t tries = 0; tries < UINT64_MAX; tries += batch_size) {
+        #pragma omp parallel for firstprivate(priv_key_shadow) shared(longest_match, tries, batch_size, hex_prefix, prefix_chars_len) schedule(static) default(none)
+
+        for (uint64_t batch = tries; batch < (tries + batch_size); batch++) {
+            uint8_t *priv_key = (uint8_t *) priv_key_shadow;
+            uint64_t *counter = priv_key_shadow + 2;
+            *counter += batch;
+            uint8_t pub_key[KEY_LEN] = {0};
+
+            crypto_scalarmult_curve25519_base(pub_key, priv_key);
+
+            uint32_t matching = (uint32_t) match_hex_prefix(pub_key, hex_prefix, prefix_chars_len);
+
+            // Global compare and update
+            uint32_t l_longest_match;
+            #pragma omp atomic read
+            l_longest_match = longest_match;
+
+            if (matching > l_longest_match) {
+                #pragma omp atomic write
+                longest_match = matching;
+
+                #pragma omp critical
+                {
+                    printf("Longest match after ~%e tries\n", (double)batch);
+                    printf("Public key: ");
+                    print_key(pub_key);
+                    printf("\nSecret key: ");
+                    print_key(priv_key);
+                    printf("\n");
+                }
             }
         }
 
-        ++num_tries;
+        seconds_passed = difftime(time(NULL), start_time);
+
+        if (longest_match >= prefix_chars_len) {
+            printf("Runtime: %lus, Calculating %e keys/s\n", (unsigned long) seconds_passed, (tries + batch_size) / seconds_passed);
+            printf("Found matching prefix, exiting...\n");
+            return 0;
+        }
+
+        if (seconds_passed - old_seconds_passed > 5.0) {
+            old_seconds_passed = seconds_passed;
+            printf("Runtime: %lus, Calculating %e keys/s\n", (unsigned long) seconds_passed, (tries + batch_size) / seconds_passed);
+            fflush(stdout);
+        }
+
     }
 
-    printf("Public key:\n");
-    print_key(pub_key);
-    printf("\nPrivate key:\n");
+    *counter = 0;
+    printf("Didn't find anything from:\n");
+    print_key(priv_key);
+    printf("\nto:\n");
+    *counter = UINT64_MAX;
     print_key(priv_key);
-    printf("\n %llu keys tried\n", num_tries);
-    return 0;
+    printf("\n");
+    return -2;
 }