perf: improve speed of cracker.c

- more inteligent secret key generation
- use OpenMP for multithreading
- leave old cracker, because it's simple
- update old cracker to new coding style

Author: sudden6

CMakeLists.txt

@@ -529,6 +529,15 @@ 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 +9,153 @@
  * 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
+// Maximum number of bytes this program can crack in one run
+#define MAX_CRACK_BYTES 8
+// Maximum length of hex encoded prefix
+#define MAX_HEX_PREFIX_LEN (MAX_CRACK_BYTES * 2)
 
-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;
+}
+
+static void cracker_core(uint64_t range_start, uint64_t range_end, uint64_t range_offs, uint64_t priv_key_shadow[4],
+                         uint32_t *longest_match, uint8_t hex_prefix[MAX_CRACK_BYTES], size_t prefix_chars_len)
+{
+    #pragma omp parallel for firstprivate(priv_key_shadow) shared(longest_match, range_start, range_end, range_offs, hex_prefix, prefix_chars_len) schedule(static) default(none)
+
+    for (uint64_t batch = range_start; batch < range_end; batch++) {
+        uint8_t *priv_key = (uint8_t *) priv_key_shadow;
+        /*
+         * 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;
+        /*
+         * Add to `counter` instead of assign here, to preservere more randomness on short runs
+         * There can be an intentional overflow in `batch + range_offs`
+         */
+        *counter += batch + range_offs;
+        uint8_t pub_key[KEY_LEN] = {0};
+
+        crypto_scalarmult_curve25519_base(pub_key, priv_key);
+
+        const unsigned matching = (unsigned) 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("%u chars matching: \n", matching);
+                printf("Public key: ");
+                print_key(pub_key);
+                printf("\nSecret key: ");
+                print_key(priv_key);
+                printf("\n");
+            }
+        }
+    }
+}
+
+void print_stats(double seconds_passed, double keys_tried)
+{
+    printf("Runtime: %10lus, Keys tried %e/%e, Calculating %e keys/s\n",
+           (unsigned long) seconds_passed, keys_tried, (double) UINT64_MAX, keys_tried / seconds_passed);
+}
 
 int main(int argc, char *argv[])
 {
@@ -37,43 +164,89 @@ int main(int argc, char *argv[])
         return 0;
     }
 
-    long long unsigned int num_tries = 0;
+    const 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 (prefix_chars_len > MAX_HEX_PREFIX_LEN) {
+        printf("Finding a key with more than 16 hex chars as prefix is not supported\n");
+        return 1;
+    }
+
+    uint8_t hex_prefix[MAX_CRACK_BYTES] = {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];
+    const size_t prefix_len = hex_string_to_bin(argv[1], prefix_chars_len, hex_prefix);
 
-    if (len > 32) {
-        len = 32;
+    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);
 
-        if (memcmp(c_key, pub_key, len) == 0) {
-            break;
-        }
+    // Declare private key bytes as uint64_t[4] so we can lower the alignment without problems
+    uint64_t priv_key_shadow[KEY_LEN / 8];
+    uint8_t *priv_key = (uint8_t *) priv_key_shadow;
+    //  Put randomness into the key
+    randombytes(priv_key, KEY_LEN);
+    uint32_t longest_match = 0;
 
-        for (i = 32; i != 0; --i) {
-            priv_key[i - 1] += 1;
 
-            if (priv_key[i - 1] != 0) {
-                break;
-            }
+    // Finishes a batch every ~10s on my PC
+    const uint64_t batch_size = (UINT64_C(1) << 18) * NUM_THREADS();
+
+    // calculate remaining batch that doesn't fit the main loop
+    const uint64_t rem_batch_size = UINT64_MAX % batch_size;
+
+    const uint64_t rem_start = UINT64_MAX - rem_batch_size - 1;
+
+    cracker_core(rem_start, UINT64_MAX, 1, priv_key_shadow, &longest_match, hex_prefix, prefix_chars_len);
+
+    double seconds_passed = difftime(time(NULL), start_time);
+    double old_seconds_passed = seconds_passed;
+
+    // Reduce time to first stats output
+    print_stats(seconds_passed, rem_batch_size + 1);
+
+    if (longest_match >= prefix_chars_len) {
+        printf("Found matching prefix, exiting...\n");
+        return 0;
+    }
+
+
+    for (uint64_t tries = 0; tries < rem_start; tries += batch_size) {
+        cracker_core(tries, tries + batch_size, 0, priv_key_shadow, &longest_match, hex_prefix, prefix_chars_len);
+
+        seconds_passed = difftime(time(NULL), start_time);
+        // Use double type to avoid overflow in addition, we don't need precision here anyway
+        double keys_tried = ((double) tries) + rem_batch_size + 1;
+
+        if (longest_match >= prefix_chars_len) {
+            print_stats(seconds_passed, keys_tried);
+            printf("Found matching prefix, exiting...\n");
+            return 0;
         }
 
-        ++num_tries;
+        // Rate limit output
+        if (seconds_passed - old_seconds_passed > 5.0) {
+            old_seconds_passed = seconds_passed;
+            print_stats(seconds_passed, keys_tried);
+            fflush(stdout);
+        }
     }
 
-    printf("Public key:\n");
-    print_key(pub_key);
-    printf("\nPrivate key:\n");
+    printf("Congrats future person who successfully searched a key space of 2^64\n");
+    uint64_t *counter = priv_key_shadow + 2;
+    *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;
 }

other/fun/cracker_simple.c

@@ -0,0 +1,84 @@
+/* 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>
+
+/* Sodium includes*/
+#include <sodium/crypto_scalarmult_curve25519.h>
+#include <sodium/randombytes.h>
+
+#include "../../testing/misc_tools.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 = hex_string_to_bin(argv[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;
+}