public function getPasswordHasher()
    {
        if ($this->_passwordHasher === null) {
            $passwordHasher = $this->getConfig('passwordHasher');
            if ($passwordHasher !== null) {
                $passwordHasher = PasswordHasherFactory::build($passwordHasher);
            } else {
                $passwordHasher = $this->_getPasswordHasher();
            }
            $this->_passwordHasher = $passwordHasher;
        }

        return $this->_passwordHasher;
    }