rev/vault_door_6

rev/vault_door_6/VaultDoor6.java

@@ -0,0 +1,42 @@
+import java.util.*;
+
+class VaultDoor6 {
+    public static void main(String args[]) {
+        VaultDoor6 vaultDoor = new VaultDoor6();
+        Scanner scanner = new Scanner(System.in);
+        System.out.print("Enter vault password: ");
+        String userInput = scanner.next();
+	String input = userInput.substring("picoCTF{".length(),userInput.length()-1);
+	if (vaultDoor.checkPassword(input)) {
+	    System.out.println("Access granted.");
+	} else {
+	    System.out.println("Access denied!");
+        }
+    }
+
+    // Dr. Evil gave me a book called Applied Cryptography by Bruce Schneier,
+    // and I learned this really cool encryption system. This will be the
+    // strongest vault door in Dr. Evil's entire evil volcano compound for sure!
+    // Well, I didn't exactly read the *whole* book, but I'm sure there's
+    // nothing important in the last 750 pages.
+    //
+    // -Minion #3091
+    public boolean checkPassword(String password) {
+        if (password.length() != 32) {
+            return false;
+        }
+        byte[] passBytes = password.getBytes();
+        byte[] myBytes = {
+            0x3b, 0x65, 0x21, 0xa , 0x38, 0x0 , 0x36, 0x1d,
+            0xa , 0x3d, 0x61, 0x27, 0x11, 0x66, 0x27, 0xa ,
+            0x21, 0x1d, 0x61, 0x3b, 0xa , 0x2d, 0x65, 0x27,
+            0xa , 0x33, 0x34, 0x34, 0x30, 0x6d, 0x37, 0x61,
+        };
+        for (int i=0; i<32; i++) {
+            if (((passBytes[i] ^ 0x55) - myBytes[i]) != 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+}

rev/vault_door_6/solve.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+
+# byte[] myBytes = {
+#     0x3b, 0x65, 0x21, 0xa , 0x38, 0x0 , 0x36, 0x1d,
+#     0xa , 0x3d, 0x61, 0x27, 0x11, 0x66, 0x27, 0xa ,
+#     0x21, 0x1d, 0x61, 0x3b, 0xa , 0x2d, 0x65, 0x27,
+#     0xa , 0x33, 0x34, 0x34, 0x30, 0x6d, 0x37, 0x61,
+# };
+# for (int i=0; i<32; i++) {
+#     if (((passBytes[i] ^ 0x55) - myBytes[i]) != 0) {
+#         return false;
+#     }
+# }
+
+my_bytes = [
+    0x3b, 0x65, 0x21, 0xa , 0x38, 0x0 , 0x36, 0x1d,
+    0xa , 0x3d, 0x61, 0x27, 0x11, 0x66, 0x27, 0xa ,
+    0x21, 0x1d, 0x61, 0x3b, 0xa , 0x2d, 0x65, 0x27,
+    0xa , 0x33, 0x34, 0x34, 0x30, 0x6d, 0x37, 0x61,
+];
+
+def main():
+    print('picoCTF{', end='')
+    for x in my_bytes:
+        print(chr(x ^ 0x55), end='')
+    print('}')
+
+if __name__ == '__main__':
+    main()
+