protected function getAuthForLogin()
	{
		// If a "key" was specified in the auth credentials, we will load it into a
		// secure RSA key instance, which will be used to connect to the servers
		// in place of a password, and avoids the developer specifying a pass.
		if ($this->hasRsaKey())
		{
			return $this->loadRsaKey($this->auth);
		}

		// If a plain password was set on the auth credentials, we will just return
		// that as it can be used to connect to the server. This will be used if
		// there is no RSA key and it gets specified in the credential arrays.
		elseif (isset($this->auth['password']))
		{
			return $this->auth['password'];
		}

		throw new \InvalidArgumentException('Password / key is required.');
	}