class PrivateKey

class PrivateKey {
    
    /**
     * The state service.
     *
     * @var \Drupal\Core\State\StateInterface
     */
    protected $state;
    
    /**
     * Constructs the private key object.
     *
     * @param \Drupal\Core\State\StateInterface $state
     *   The state service.
     */
    public 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);
    }

}