藍芽環境中基於通行碼的認證機制

Abstract

藍芽在現今短距離傳輸上扮演著重要的角色。無論是行動裝置或是固定不動的設備，只要運用藍芽，在短距內便能自由的傳輸資料。當兩台俱備藍芽功能的裝置欲互相連結時，需要先經過裝置配對的過程，從安全的角度來看，這個過程主要是認證彼此並建立一把秘密金鑰。本篇論文針對藍芽中基於通行碼認證金鑰交換協定提出安全分析，發現新的認證機制非常易於遭受通行碼猜測攻擊，而我們也明確的點出其設計方法若僅微幅調整將無法完全的抵禦。接著，提出一個能夠有效防禦猜測攻擊的協定，安全層級提升且訊息交換量也可降低。此外，我們正規的證明提出的協定在random oracle model下是安全的。此協定不改變傳統藍芽使用者的操作習慣，且計算複雜度低，適合替代藍芽現有的通行碼驗證機制。

Bluetooth is a popular wireless communication technique, providing connection between portable or stationary devices in close range. A procedure called pairing needs to be performed when two devices intend to connect with each other in order to form a trusted pair and generate secret keys to protect the link. There are several modes of Bluetooth pairing, and password-based is the most convenient and prevalent way. In this paper, we pointed out a potential vulnerability in the password-based pairing protocol of the latest Bluetooth v3.0, which makes password guessing possible. To cope with the problem, a new scheme is proposed which can mitigate the network threats, and is compatible with the hardware of legacy Bluetooth devices. Not only heuristic analysis and its physical meaning will be provided, but also formal proof will be given to make sure that our proposed protocol is secure. Note that our modification does not affect Bluetooth users’ custom, which makes it a suitable replacement for the new Bluetooth pairing protocol.