Vehicular ad-hoc networks (VANETs) have several security issues such as privacy preservation, secure authentication, and system reliability. In the VANET, a vehicle communicates with other vehicles or infrastructures using broadcasting messages. These messages contain not only normal traffic information, but also identification information of sender. In general, the identification information remains encrypted to ensure privacy. However, the conventional centralized system can decrypt the identification information using private information of the sender vehicle. As a result, the central server can often be targeted by adversaries. We propose a message authentication scheme for anonymity and decentralization of information using blockchain technology. Here, we introduce public-private key and message authentication code (MAC) for secure authentication. In this paper, we adopt consensus algorithms for composing blockchain system such as the proof of work (PoW) and Practical Byzantine Fault Tolerance (PBFT) into the proposed authentication process. Finally, we demonstrate that the proposed method is secure from the attacks which include impersonation from internal attacker as well as typical attacks.

With the development of blockchain technology, participants need to have huge storage volumes to deal with the growing blockchain ledger size over time. This requirement leads to the conditional participation and verification of participants, thus weakening the decentralization of a blockchain system. Several compression schemes have been proposed to mitigate this storage problem by compressing a blockchain ledger based on redundancy, modular functions, and hash functions. However, these schemes have the limitation of accumulating the compression results to validate the retained blocks. The accumulation gradually reduces the storage volume for the blockchain ledger within the storage volume of nodes with limited resources, thus reducing the verification capability of the nodes. In this paper, a selective compression scheme using a checkpoint-chain is proposed to prevent the accumulation of compression results. The checkpoint-chain is a second blockchain that stores the checkpoints compressing existing blocks through a block Merkle tree. An update process is also proposed to prevent the accumulation of checkpoints by combining them. As numerous blocks can be verified with only a few updated checkpoints, blockchain nodes with limited resources can reduce the storage volume for the blockchain ledger and achieve high verification capabilities. Finally, compared with the existing compression schemes, the proposed scheme can achieve an average reduction in the storage overhead and an average increase in the verification capability of 76.02% and 13.90%, respectively. Moreover, the corresponding performance improvements are 86.14% and 15.44% when the update process is performed, respectively.

One significant security challenge in vehicular networks is defending against malicious members’ attacks, including insiders and compromised authorities. Insiders are legitimate vehicles who have passed the registration process. Since they can exploit all the information related to the network and other members’ communication, it is easier to perform various attacks with a high impact. In addition, an authority takes charge of registering and managing legitimate vehicles. Thus, if the authority is compromised, it will cause significant damage to the system, including the leaking of private information, such as identity, location, and membership. Many authentication schemes have been proposed to protect vehicular communication from these security issues. However, most existing schemes still face the vulnerability of malicious members. Furthermore, most conventional schemes require additional interactions between the vehicles and infrastructure for authentication, which can cause communication overheads. To overcome these issues, we propose a novel blockchain-based one-time authentication scheme to protect vehicular communication against malicious members. One-time authentication provides higher security and efficiency as every message is authenticated with different proof at a time. We use publicly verifiable secret sharing with blockchain for this property, which brings two benefits. First, it prevents even an authority from obtaining members’ identities by distributing encrypted shares instead of their real identities. Second, it enables robust vehicular communication against insiders’ attacks by allowing a vehicle to send unique proof generated from its private information with messages. Receivers can authenticate the messages by comparing attached values to the information through the blockchain in a noninteractive manner. Security analysis shows that our scheme assures secure vehicle-to-everything communication against insider attacks, and efficiency analysis shows how both authentication and consensus delay change.

This paper proposes a secure key exchange scheme for Wi-Fi Protected Access II preshared key (WPA2-PSK)-based public Wi-Fi networks. The existing public Wi-Fi networks have several vulnerabilities, which are caused by eavesdropping stations in the same network. The main problem is that all stations in the same network have the same pre-shared key after the association. The attackers can derive an encryption key by eavesdropping on the four-way handshake procedure. Thus, we apply an elliptic curve public key cryptography concept to the proposed scheme to keep the key safe. In the proposed scheme, only an access point (AP) has its public key and private key pair. The proposed scheme solves the problem by exchanging a secondary key that each user determines or generated in the station during the authentication procedure. In the proposed scheme, the secondary key is encrypted by a station before it is transmitted to the AP. The AP can only decrypt the encrypted authentication message using its private key. By using the secondary key, each user can generate a unique pre-shared key and other following keys, which are derived from the four-way handshake procedure. Therefore, the exchange of the secondary key can defend against attacks from the malicious station in the same network. The safety of the proposed scheme is analyzed by several attack scenarios defined in this paper. Consequently, the proposed scheme provides more security level, 192 bits or 256 bits, compared with the conventional WPA2-PSK-based public Wi-Fi networks.

본 논문에서는 멀티 모바일 싱크를 사용하는 무선 센서 네트워크에서 블록체인과 비밀 공유 기법을 적용한 안전하고 신뢰성있는 데이터 전송 기법을 제안한다. 무선 센서 네트워크는 다수의 한정된 자원을 가진 센서 노드로 구성된 무선 네트워크이다. 자원이 한정적인 센서 노드들은 저전력 문제를 겪기 때문에 무인 항공 기체 등의 모바일 싱크를 활용하는 방법들이 제안되어 왔다. 하지만 모바일 싱크를 활용하는 시스템에서 센서 노드가 생성한 데이터를 전송할 때 데이터 유출, 데이터 위변조, 기능 장애와 같은 보안 및 신뢰성 문제가 발생할 수 있다. 본 논문에서 제안하는 기법은 비밀 공유 기법을 통해 원본 데이터를 공유값으로 분산저장하여 데이터 유출을 방지할 수 있으며 블록체인 기술을 활용하여 데이터 위변조와 기능 장애와 같은 문제들로부터 견고하다. 또한 보안 분석을 제시하여 제안하는 기법이 고려하고 있는 보안 위협으로부터 안전하다는 것을 증명한다.