The security of Low-Power Wide-Area Network (LPWAN) mainly relies on encryption for ensuring packet integrity and confidentiality. Unfortunately, the latest LPWAN specifications refrain from specifying how to distribute keys for encryption. In this paper, we tackle this problem via physical layer security, which exploits the channel characteristics to generate secret keys at the physical layer. In order to generate consistent keys from noisy feature sources and to achieve high reconciliation success rate, we propose FLoRa, a physical layer key generation system for LPWAN based on sequential fuzzy extractor. An adaptive multi-bit quantization algorithm is first proposed to generate the initial key, which accelerates the bit generation rate at the start-up procedure. We then design a novel fuzzy extractor by sequentially slicing the initial key, which improves the reconciliation success rate, as well as reduces the key reconciliation time. We implement FLoRa in a LoRaWAN based network prototype and evaluate it by conducting extensive indoor and outdoor experiments. Experimental results reveal that FLoRa is capable of generating consistent secret keys with high key generation performance in both static and dynamic network environments.

低功耗广域网 (LPWAN) 的安全性主要依靠加密来确保数据包的完整性和机密性。不幸的是，最新的 LPWAN 规范没有指定如何分发加密密钥。在本文中，我们通过物理层安全来解决这个问题，它利用信道特性在物理层生成密钥。为了从嘈杂的特征源生成一致的密钥并实现高协调成功率，我们提出了 FLoRa，一种基于顺序模糊提取器的 LPWAN 物理层密钥生成系统。首先提出了一种自适应多比特量化算法来生成初始密钥，从而加快了启动过程中的比特生成速率。然后我们通过顺序切片初始键来设计一个新的模糊提取器，提高了对账成功率，减少了密钥对账时间。我们在基于 LoRaWAN 的网络原型中实施 FLoRa，并通过进行广泛的室内和室外实验对其进行评估。实验结果表明，FLoRa 能够在静态和动态网络环境中生成具有高密钥生成性能的一致密钥。