| 摘要: | 如何確保車輛安全訊息傳輸穩定性是一項重要的議題。若訊息能被正確的傳播及儲存，政府及相關單位便可利用記錄之數據進行相關安全應用程式開發。但車載網路中的節點眾多，網路拓樸動態性極高，每個節點傳遞的安全訊息會對儲存空間造成重大負擔。區塊鏈做為新興的分散式資料庫儲存技術，具備難以竄改、去中心化的特性，適合保存車輛傳輸的安全相關訊息，更能應付其動態的拓樸環境。但是區塊鏈同時也有擴充性的挑戰，其無限制增長的特點會隨著運行時間越長，對功耗的需求越大，使車輛無法承擔挖礦的成本。區塊鏈剪枝便是解決區塊鏈擴充性的方案之一，去除區塊中較不重要的資訊，使區塊鏈更適用於車載環境。
本論文提出基於選擇性區塊鏈剪枝的安全訊息傳播機制，訊息傳輸基於WAVE/DSRC通訊協定，並採用SAE J2735標準，將安全訊息封裝成BSM訊息集。同時，藉由PoA共識演算法及剪枝技術來確保區塊鏈的長久運行。PoA機制具備高吞吐量、可擴展性，相較於其他公有鏈共識機制，更適用於車載環境。此外，為減緩PoA機制過度集中化的問題，設計名譽獎懲機制，降低集中化的程度，避免特定節點長期掌握驗證區塊的權力，導致惡意行為的發生。同時，剪枝過程以車輛的速度、事故訊息等，來判斷區塊紀錄的資訊是否重要，在剪枝的同時確保關鍵數據不會遺失。
實驗結果顯示，本論文設計之私有鏈相較於以太坊測試網路Ropsten及Rinkeby有更快的區塊產出速度，分別可降低59.96% 和 64.01% 的區塊產出時間。名譽獎懲機制使區塊驗證權利平均分佈，和估計值僅有10.08% 差異。此外，提出之剪枝演算法能夠降低68.01% 的儲存空間消耗，同時保留重要車載數據。
;How to ensure the stability of vehicle safety information transmission is an important issue. If the information can be properly disseminated and stored, the government and relevant units can use the recorded data to develop relevant security applications. However, there are many nodes in the in-vehicle network, the network topology is extremely dynamic, and the marking information transmitted by each node will cause a heavy burden on the storage space. As an emerging decentralized database storage technology, blockchain has the characteristics of being difficult to tamper with and decentralized management. It is suitable for saving safety-related information transmitted by vehicles, and can better cope with its dynamic topology environment. However, the blockchain also has scalability challenges. The unlimited growth feature will increase the demand for power consumption as the running time increases, making the vehicle unable to bear the cost of mining. Blockchain pruning is one of the solutions to the scalability of the blockchain, removing less important information in the block and making the blockchain more suitable for the vehicle environment.
This paper proposes a secure message dissemination mechanism based on selective blockchain pruning. Blockchain is considered one of the solutions to improve VAENTs architecture because of its non-tamper and decentralized characteristics. But low throughput and scalability of blockchain is a challenge, and the nodes in VAENTs can not handle a large amount of computing demand. The Proof of Authority (PoA) consensus mechanism sacrifices the decentralized nature of blockchain for centralized management in exchange for high throughput and scalability, which is more suitable for VANETs. Also, because there is no miner in PoA, it can avoid the problem of high carbon emissions during blockchain operations and ensure that it does not cause environmental issues. At the same time, design a reputation mechanism to mitigate the centralization situation and avoid malicious behavior to guarantee the average distribution of block generation rights. The proposed selective blockchain pruning mechanism selects the speed of the vehicle and accident information as references to determine whether the data recorded in the blockchain is important or not. The pruning mechanism can reduce storage space consumption while preserving important data.
The experimental results show that the blockchain designed in this paper has a faster block generation speed compared with Ropsten and Rinkeby, the Ethereum test network, which can reduce the block generation time by 59.96% and 64.01%, respectively. The reputation mechanism enables the average distribution of block generation rights, which differs from the estimated value by only 10.08%. In addition, the proposed pruning mechanism can reduce the storage space consumption by 68.01%. |
