Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/lib/Drupal/Core/PrivateKey.php

@@ -0,0 +1,70 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\PrivateKey.
+ */
+
+namespace Drupal\Core;
+
+use Drupal\Core\State\StateInterface;
+use Drupal\Component\Utility\Crypt;
+
+/**
+ * Manages the Drupal private key.
+ */
+class PrivateKey {
+
+  /**
+   * The state service.
+   *
+   * @var \Drupal\Core\State\StateInterface
+   */
+  protected $state;
+
+  /**
+   * Constructs the token generator.
+   *
+   * @param \Drupal\Core\State\StateInterface $state
+   *   The state service.
+   */
+  function __construct(StateInterface $state) {
+    $this->state = $state;
+  }
+
+  /**
+   * Gets the private key.
+   *
+   * @return string
+   *   The private key.
+   */
+  public function get() {
+    if (!$key = $this->state->get('system.private_key')) {
+      $key = $this->create();
+      $this->set($key);
+    }
+
+    return $key;
+  }
+
+  /**
+   * Sets the private key.
+   *
+   * @param string $key
+   *  The private key to set.
+   */
+  public function set($key) {
+    return $this->state->set('system.private_key', $key);
+  }
+
+  /**
+   * Creates a new private key.
+   *
+   * @return string
+   *   The private key.
+   */
+  protected function create() {
+    return Crypt::randomBytesBase64(55);
+  }
+
+}