隨著車載隨意行動網路從車用網路邁入車聯網時代，透過裝置間訊息交換而延伸出來的的應用也越來越多，例如透過車輛的位置與速度獲得交通流暢度資訊，或是緊急事故資訊發布等等，而乘載這些資訊的車聯網應用的安全通訊傳輸管道也因此越來越重要。車聯網環境時常仰賴於廣播通訊，如何在安全又有效率的狀況下進行廣播通訊，成為一個很重要的研究課題。

在這篇論文中，我們主要使用基於身分的廣播加密，為車對車通訊打造保有隱私且安全又有效率的廣播通訊協定，透過群體通訊加密機制中，訊息發起者針對每一個廣播訊息只要加密一次，即可發送廣播訊息給群體，讓所有指定的接收者解密，以降低使用的運算與傳輸資源，提升效率。在提供輕量加密機制的同時，也能保有隱私、抵禦重送攻擊與偽造攻擊。我們也提出了透過路邊通訊單元發出群體重組訊號，在車流交會量最大的道路入口處進行重組，以達到最高的群體重組效率。最後，我們也提出了在不更換所有群組成員的公開金鑰下動態加入此群體的方式，避免行駛其間有新成員加入即須所有人都更換金鑰的效能浪費。

As applications of the Vehicles communication transits from Vehicular Ad-hoc Network to Internet of Vehicles era, more and more vehicular and traffic applications arise: real-time traffic condition information, emergency accident information...and so forth. Thus, it is crucial to provide secure transmission channels for the data exchange of these IoV applications. IoV also utilizes broadcast communication primarily, especially for V2V communications. Providing fast and efficient broadcast communication has been a hot research topic.

In this thesis, we constructed a secure and efficient broadcast communication scheme for V2V communications. The message sender only needs to encrypt the message once before broadcasting, and all the eligible receivers in the group can decrypt the message after receiving it, thus lowering the computation and transmission resources requirements. Besides the lightweight encryption mechanism, the scheme also preserves privacy and avoids reply and impersonation attacks. We also provide a way to establish the group and re-grouping in the road entrance of limited access roads through Road Side Units to provide the highest re-grouping efficiency. At last, the mechanism also comes with dynamic group member joining, that the joining of a new member does not require re-keying every other member's public key to avoid the need for resource consumption.

RecommendationLetter ... i
ApprovalLetter ... ii
Abstract in Chinese ... iii
Abstract in English ... iv
Acknowledgements ... v
Contents ... vi
List of Figures ... viii
List of Tables ... ix
1 Introduction ... 1
2 Preliminaries ... 4
2.1 BilinearMaps ... 4
2.2 Identity-Based Broadcast Encryption . . . 4
2.3 Public Key Encryption ... 5
3 RelatedWork ... 8
4 ProposedMechanism ... 11
4.1 RSUBeaconVerificationProtocol . . . 13
4.2 GroupEstablishmentPhase... 13
4.3 GroupKeySetupPhase... 15
4.4 EncryptionPhase ... 16
4.5 DecryptionPhase ... 17
4.6 VehicleLeavingGroup ... 17
4.7 DynamicGroupJoining... 18
5 SecurityAnalysis ... 20
6 Conclusions ... 22
References... 23

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