1 files changed, 56 insertions, 0 deletions
diff --git a/day4/day4.c b/day4/day4.c
new file mode 100644
index 0000000..339ea1a
--- /dev/null
+++ b/day4/day4.c
@@ -0,0 +1,56 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <openssl/md5.h>
+
+unsigned char secret[10];
+unsigned char target[10];
+unsigned char result[MD5_DIGEST_LENGTH];
+
+void hash(int i) {
+  char num[12];
+  sprintf(num, "%d", i);
+  char str[22] = "";
+  strcat(str, secret);
+  strcat(str, num);
+
+  MD5(str, strlen(str), result);
+}
+
+int tohex() {
+  int i, dg = 0;
+  for(i = 0; i < 4; i++) {
+    dg <<= 8;
+    dg += result[i];
+  }
+  return dg;
+}
+
+int check(int len) {
+  unsigned char str[8];
+  int dg = tohex();
+  sprintf(str, "%08x", dg);
+  return strncmp(str, target, len) == 0;
+}
+
+int main() {
+  int i = 1, got5 = 0, got6 = 0;
+
+  scanf("%s", secret);
+  scanf("%s", target);
+
+  while(!(got5 && got6)) {
+    hash(i);
+    if(!got5 && check(5)) {
+      got5 = 1;
+      printf("Lowest number for 5-zeroes hash: %d\n", i);
+    }
+    if(!got6 && check(6)) {
+      got6 = 1;
+      printf("Lowest number for 6-zeroes hash: %d\n", i);
+    }
+    i++;
+  }
+
+  return 0;
+}