Support resetting user's master password.

platform-independent/java/model/src/main/java/com/lyndir/masterpassword/model/MPUser.java

@@ -77,8 +77,18 @@ public interface MPUser<S extends MPSite<?>> extends Comparable<MPUser<?>> {
     void authenticate(MPMasterKey masterKey)
             throws MPIncorrectMasterPasswordException, MPKeyUnavailableException, MPAlgorithmException;
 
+    /**
+     * Clear all authentication tokens and secrets from memory, effectively logging the user out.
+     */
     void invalidate();
 
+    /**
+     * Wipe the key ID, allowing the user to {@link #authenticate(char[])} with any master password.
+     *
+     * Note: Authenticating with a different master password will cause all of the user's results to change.
+     */
+    void reset();
+
     boolean isMasterKeyAvailable();
 
     @Nonnull

platform-independent/java/model/src/main/java/com/lyndir/masterpassword/model/impl/MPBasicUser.java

@@ -97,12 +97,14 @@ public abstract class MPBasicUser<S extends MPBasicSite<?, ?>> extends Changeabl
     @Override
     public byte[] getKeyID() {
         try {
-            return getMasterKey().getKeyID( getAlgorithm() );
+            if (isMasterKeyAvailable())
+                return getMasterKey().getKeyID( getAlgorithm() );
         }
         catch (final MPException e) {
             logger.wrn( e, "While deriving key ID for user: %s", this );
-            return null;
         }
+
+        return null;
     }
 
     @Nullable
@@ -143,23 +145,29 @@ public abstract class MPBasicUser<S extends MPBasicSite<?, ?>> extends Changeabl
     public void invalidate() {
         if (masterKey == null)
             return;
-        
-        this.masterKey = null;
+
+        masterKey.invalidate();
+        masterKey = null;
 
         for (final Listener listener : listeners)
             listener.onUserInvalidated( this );
     }
 
+    @Override
+    public void reset() {
+        invalidate();
+    }
+
     @Override
     public boolean isMasterKeyAvailable() {
-        return masterKey != null;
+        return (masterKey != null) && masterKey.isValid();
     }
 
     @Nonnull
     @Override
     public MPMasterKey getMasterKey()
             throws MPKeyUnavailableException {
-        if (masterKey == null)
+        if ((masterKey == null) || !masterKey.isValid())
             throw new MPKeyUnavailableException( "Master key was not yet set for: " + this );
 
         return masterKey;

platform-independent/java/model/src/main/java/com/lyndir/masterpassword/model/impl/MPFileUser.java

@@ -169,6 +169,13 @@ public class MPFileUser extends MPBasicUser<MPFileSite> {
         }
     }
 
+    @Override
+    public void reset() {
+        keyID = null;
+
+        super.reset();
+    }
+
     @Override
     public MPFileSite addSite(final String siteName) {
         return addSite( new MPFileSite( this, siteName ) );