Added a RandomString class from stackoverflow, to generate random alphanumeric strings (to be used as passwords).

Added some code to VaultDoor, including random password generation and code to encrypt/decrypt under a Vernam-like cypher.
Modified door opening policy to include the possibility of keeping the door open.

Plugin Vault/src/main/java/net/simon987/vaultplugin/InvalidCharsetException.java

@@ -0,0 +1,16 @@
+public class InvalidCharsetException extends Exception {
+    public InvalidCharsetException () {
+
+    }
+
+    public InvalidCharsetException (String message) {
+        super (message);
+    }
+
+    public InvalidCharsetException (Throwable cause) {
+        super (cause);
+    }
+
+    public InvalidCharsetException (String message, Throwable cause) {
+        super (message, cause);
+    }

Plugin Vault/src/main/java/net/simon987/vaultplugin/RandomString.java

@@ -0,0 +1,68 @@
+/**
+ *
+ * RandomString class by erickson
+ * https://stackoverflow.com/questions/41107/how-to-generate-a-random-alpha-numeric-string
+ *
+ */
+
+
+import java.security.SecureRandom;
+import java.util.Locale;
+import java.util.Objects;
+import java.util.Random;
+
+public class RandomString {
+
+    /**
+     * Generate a random string.
+     */
+    public String nextString() {
+        for (int idx = 0; idx < buf.length; ++idx)
+            buf[idx] = symbols[random.nextInt(symbols.length)];
+        return new String(buf);
+    }
+
+    public static final String upper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+    public static final String lower = upper.toLowerCase(Locale.ROOT);
+
+    public static final String digits = "0123456789";
+
+    public static final String alphanum = upper + lower + digits;
+
+    private final Random random;
+
+    private final char[] symbols;
+
+    private final char[] buf;
+
+    public RandomString(int length, Random random, String symbols) {
+        if (length < 1) throw new IllegalArgumentException();
+        if (symbols.length() < 2) throw new IllegalArgumentException();
+        this.random = Objects.requireNonNull(random);
+        this.symbols = symbols.toCharArray();
+        this.buf = new char[length];
+    }
+
+    /**
+     * Create an alphanumeric string generator.
+     */
+    public RandomString(int length, Random random) {
+        this(length, random, alphanum);
+    }
+
+    /**
+     * Create an alphanumeric strings from a secure generator.
+     */
+    public RandomString(int length) {
+        this(length, new SecureRandom());
+    }
+
+    /**
+     * Create session identifiers.
+     */
+    public RandomString() {
+        this(21);
+    }
+
+}

Plugin Vault/src/main/java/net/simon987/vaultplugin/VaultDoor.java

@@ -6,6 +6,7 @@ import net.simon987.server.game.GameObject;
 import net.simon987.server.game.Programmable;
 import net.simon987.server.game.Updatable;
 import net.simon987.server.logging.LogManager;
+import net.simon987.vaultplugin.RandomString;
 
 import java.util.Arrays;
 
@@ -19,77 +20,148 @@ public class VaultDoor extends GameObject implements Programmable, Enterable, Up
      */
     private char[] password;
 
+    private RandomString random_string_generator;
+
     /**
      * Whether or not the vault door is opened
      */
-    private boolean opened;
+    private boolean open = false;
 
-    private int openedTimer;
 
     /**
      * Number of ticks to remain the door open
      */
-    private static final int OPEN_TIME = 4; //todo load from config
+    private int OPEN_TIME = GameServer.INSTANCE.getConfig().getInt("vault_door_open_time");
+    private int openedTimer = 0;
+
+    private int password_length;
+    private int cypher_id;
+
+    public VaultDoor(int password_length, int cypher_id){
+        this.password_length = password_length;
+        this.cypher_id = cypher_id;
+        this.random_string_generator = new RandomString(password_length);
+
+        password = getRandomPassword();
+    }
 
 
     @Override
     public void update() {
-
+        if (open){
             if (openedTimer <= 0) {
-
+                //Door was open for OPEN_TIME, close it and regen password
-            //Door was opened for OPEN_TIME, close it and regen password
                 password = getRandomPassword();
-            opened = false;
+                open = false;
-
+                openedTimer = 0;
                 LogManager.LOGGER.fine("Closed Vault door ID: " + getObjectId());
-        } else {
+            } 
+            else{
                 openedTimer--;
             }
+        }
 
     }
 
     @Override
     public boolean sendMessage(char[] message) {
 
-        System.out.println("VAULT: sendMessage" + new String(message));//todo rmv
-
-        if (!opened) {
-
         if (Arrays.equals(message, password)) {
-                opened = true;
+            if (!open) {
-                openedTimer = OPEN_TIME;
+                openVault();
+            } 
+            else{
+                keepVaultOpen();
+            }
+            return true;
+        }
+        else {
+            return false;
+        }
+    }
 
+    private void openVault(){
+        open = true;
+        openedTimer = OPEN_TIME;
         LogManager.LOGGER.fine("Opened Vault door ID: " + getObjectId());
     }
 
-            return true;
+    private void keepVaultOpen(){
-        } else {
+        open = true;
-            //Can't receive messages when opened
+        openedTimer = OPEN_TIME;
-            return false;
-        }
     }  
 
     @Override
     public boolean enter(GameObject object) {
 
-        LogManager.LOGGER.fine("VAULT enter " + opened);
+        LogManager.LOGGER.fine("VAULT enter " + open);
-
-        if (opened) {
 
+        if (open) {
             //TODO: Enter in the vault
-
-
             return true;
         } else {
             return false;
         }
-
     }
 
+    /**
+     * Generates a random alphanumeric string using the RandomString class
+     */
     private static char[] getRandomPassword() {
-        return "12345678".toCharArray();//todo actual random password
+        return random_string_generator.nextString().toCharArray();
     }
 
+
+
+    private char[] encryptVernam(char[] plaintext){
+        String charset = random_string_generator.alphanum;
+        int charset_length = charset.length();
+        int plaintext_length = plaintext.length;
+        char[] cyphertext = new char[plaintext_length];
+        for (int i = 0; i< plaintext_length; i++){
+            int j = i % password_length;
+            char p = plaintext[i];
+            char q = password[j];
+            int p_ind = charset.indexOf(p);
+            if (p_ind == -1){
+                throw InvalidCharsetException("Plaintext contains non-alphanumeric character: "+p);
+            }
+            int q_ind = charset.indexOf(q);
+            if (q_ind == -1){
+                throw InvalidCharsetException("Password contains non-alphanumeric character: "+q); // this should NEVER happen
+            }
+            int c_int = (p_ind+q_ind)%charset_length;
+            char c = charset.charAt(c_int);
+            cyphertext[i] = c;
+        }
+        return cyphertext;
+    }
+
+    private char[] decryptVernam(char[] cyphertext){
+        String charset = random_string_generator.alphanum;
+        int charset_length = charset.length();
+        int cyphertext_length = cyphertext.length;
+        char[] plaintext = new char[cyphertext_length];
+        for (int i = 0; i< cyphertext_length; i++){
+            int j = i % password_length;
+            char c = cyphertext[i];
+            char q = password[j];
+            int c_ind = charset.indexOf(c);
+            if (c_ind == -1){
+                throw InvalidCharsetException("Cyphertext contains non-alphanumeric character: "+c);
+            }
+            int q_ind = charset.indexOf(q);
+            if (q_ind == -1){
+                throw InvalidCharsetException("Password contains non-alphanumeric character: "+q); // this should NEVER happen
+            }
+            int p_int = (c_ind-q_ind)%charset_length;
+            char p = charset.charAt(p_int);
+            plaintext[i] = p;
+        }
+        return plaintext;
+    }
+
+
     @Override
     public char getMapInfo() {
         return MAP_INFO;
@@ -99,4 +171,5 @@ public class VaultDoor extends GameObject implements Programmable, Enterable, Up
     public BasicDBObject mongoSerialise() {
         return null;
     }
+
 }

Server/src/main/resources/config.properties

@@ -84,3 +84,7 @@ wg_maxCopperCount=2
 # ----------------------------------------------
 # Maximum execution time of user code in ms
 user_timeout=100
+
+
+# ----------------------------------------------
+vault_door_open_time=4