diff --git a/legal.install b/legal.install
index f46c194..67dda30 100644
--- a/legal.install
+++ b/legal.install
@@ -159,6 +159,13 @@ function legal_update_6003() {
 }
 
 /**
+ * Clear the menu cache.
+ */
+function legal_update_6004() {
+  menu_rebuild();
+}
+
+/**
  * Implementation of hook_uninstall().
  */
 function legal_uninstall() {
diff --git a/legal.module b/legal.module
index e6a658b..7671319 100644
--- a/legal.module
+++ b/legal.module
@@ -82,10 +82,10 @@ function legal_menu() {
     'file' => 'legal.pages.inc',
   );
 
-  $items['legal_accept/%/%'] = array(
+  $items['legal_accept'] = array(
     'title' => 'Terms and Conditions',
     'page callback' => 'drupal_get_form',
-    'page arguments' => array('legal_login', 1, 2),
+    'page arguments' => array('legal_login'),
     'access callback' => TRUE,
     'type' => MENU_CALLBACK,
   );
@@ -305,8 +305,15 @@ function legal_user($op, &$edit, &$account, $category = FALSE) {
       unset($_REQUEST['destination']);
 
       $signatory = db_fetch_object(db_query_range('SELECT * FROM {users} WHERE uid = %d', $uid, 0, 1));
+      $token = drupal_base64_encode(hash('sha256', drupal_random_bytes(55), TRUE));
+      $hash = user_pass_rehash($signatory->pass, $token, $signatory->login, $uid);
 
-      drupal_goto('legal_accept/' . $signatory->uid . '/' . md5($signatory->name . $signatory->pass . $signatory->login), $query);
+      setcookie('legal_hash', $hash, 0, '/');
+      setcookie('legal_id', $uid, 0, '/');
+
+      $query['token'] = $token;
+
+      drupal_goto('legal_accept', $query);
       break;
 
     case 'form':
@@ -465,9 +472,38 @@ function legal_user($op, &$edit, &$account, $category = FALSE) {
 /**
  * Require registered users to accept new T&C.
  */
-function legal_login($constructor, $uid, $id_hash = NULL) {
+function legal_login($constructor) {
   global $language;
 
+  // Check we have all the data and there are no shenanigans.
+  if (!isset($_GET['token']) || !isset($_COOKIE['legal_id']) || !is_numeric($_COOKIE['legal_id']) || !isset($_COOKIE['legal_hash'])) {
+    // Delete these cookies.
+    setcookie('legal_hash', '', REQUEST_TIME - 3600, '/');
+    setcookie('legal_id', '', REQUEST_TIME - 3600, '/');
+    drupal_set_message(t('Operation timed out. Please try to log in again.'));
+    drupal_goto();
+  }
+
+  $hash = $_COOKIE['legal_hash'];
+  $uid = $_COOKIE['legal_id'];
+  $token = $_GET['token'];
+
+  $account = db_fetch_object(db_query("SELECT u.* FROM {users} u WHERE uid = %d", $uid));
+
+  // Make sure the account is real and has a last login value.
+  if (!isset($account->login)) {
+    drupal_goto();
+  }
+
+  // Limit how long $hash can be used to 1 hour.
+  // Timestamp and $hash are used to generate the authentication token.
+  if ((REQUEST_TIME - $account->login) > 3600) {
+    // Delete these cookies.
+    setcookie('legal_hash', '', REQUEST_TIME - 3600, '/');
+    setcookie('legal_id', '', REQUEST_TIME - 3600, '/');
+    drupal_goto();
+  }
+
   // Get last accepted version for this account.
   $legal_account = legal_get_accept($uid);
 
@@ -499,9 +535,14 @@ function legal_login($constructor, $uid, $id_hash = NULL) {
     '#value' => $uid,
   );
 
-  $form['id_hash'] = array(
+  $form['token'] = array(
+    '#type' => 'value',
+    '#value' => $token,
+  );
+
+  $form['hash'] = array(
     '#type' => 'value',
-    '#value' => $id_hash,
+    '#value' => $hash,
   );
 
   $form['tc_id'] = array(
@@ -543,17 +584,31 @@ function legal_login($constructor, $uid, $id_hash = NULL) {
 
 function legal_login_validate($form, &$form_state) {
   $account = db_fetch_object(db_query_range('SELECT * FROM {users} WHERE uid = %d', $form_state['values']['uid'], 0, 1));
-  $id_hash = md5($account->name . $account->pass . $account->login);
 
-  if ($id_hash != $form_state['values']['id_hash']) {
+  $hash = user_pass_rehash(
+    $account->pass,
+    $form_state['values']['token'],
+    $account->login,
+    $form_state['values']['uid']
+  );
+
+  if ($hash !== $form_state['values']['hash']) {
     form_set_error('legal_accept', t('User ID cannot be identified.'));
+    // Delete these cookies.
+    setcookie('legal_hash', '', REQUEST_TIME - 3600, '/');
+    setcookie('legal_id', '', REQUEST_TIME - 3600, '/');
     drupal_goto();
   }
 }
 
 function legal_login_submit($form, &$form_state) {
   global $user;
-    $values = $form_state['values'];
+
+  // Delete these cookies.
+  setcookie('legal_hash', '', REQUEST_TIME - 3600, '/');
+  setcookie('legal_id', '', REQUEST_TIME - 3600, '/');
+
+  $values = $form_state['values'];
   $user = user_load(array('uid' => $values['uid']));
 
   legal_save_accept($values['version'], $values['revision'], $values['language'], $user->uid);