隨著通訊技術的蓬勃發展，網路設備及手持裝置的快速增加，無線通訊已經越來越普及。如何在大量部署的物聯網(Internet of Things, IoT)裝置建立安全通訊，是目前相當重要的研究議題。然而，傳統的公開金鑰演算法(Public Key Cryptography)以及指數運算並已不適用於資源受限(Resource Constrained)裝置，使用對稱式加密演算法(Symmetric Key Cryptography)則是較適合的方式。
本研究提出適用於無線網路的金鑰管理機制，使用階層式的方式，將大群體劃分為不同群體。透過向量外積運算產生群體金鑰，降低運算成本。此外，提出有效率的金鑰更新方法，改善金鑰更新的運算成本，並符合金鑰獨立性、金鑰機密性。

With the advances in communication technology and increased numbers of Internet-connected devices/mobile devices, they have been widely used in wireless communication. It is an important research topic to make secure group communication for multiple IoT devices. However, conventional public key encryption and exponentiation computation are not suitable for resource-constrained devices. Instead, symmetric key encryption is more appropriate for them.
In this paper, we propose a key management mechanism for wireless sensor network. The proposed scheme splits a group of members into hierarchical subgroups of members. And it reduces the computation complexity for group key generation by the cross-product operation. Moreover, we also propose a computation-efficient key updating method to improve computation cost and the number of key-updating requests. It satisfies some properties such as key independence and key confidentiality.

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