## 2 Related Research
### Intelligent Transportation System
#### 2.1.3 Security Threats
In addition, when connecting a vehicle's device, a malware-infected mobile device can interfere with the vehicle's normal V2N service. The bigger problem is that V2N is also closely related to the connection between the vehicle and the cloud. That is not a problem for the vehicle's internal system, but the data stored in the cloud server could be damaged or lost because of poor cloud management. The point is that the integrity of the data can be compromised. The infringement can be an attack such as DoS or signal jamming and can create problems such as software bugs, malfunctions due to malware, and reduced service availability due to cloud server problems. Confidentiality breaches can occur, such as the code of various services through V2N being leaked through attack methods such as eavesdropping, and these threats are introduced earlier, not just breach of confidentiality. Modifying and distributing the application through reverse engineering can result in infringement of both integrity and availability, such as enabling remote forced control of the vehicle ECU as the attacker intended. Threats to Authentication  
If a private key is obtained through physical access to a vehicle, authentication can be bypassed, and the attacker can impersonate a legitimate vehicle user. In the V2I environment, communication entities such as onboard units (OBUs) and roadside units (RSUs) go through an entity authentication process that must determine that the ID is for a legitimate owner. Therefore, if a private key is obtained through physical access to an RSU or an OBU, one concern is that authentication will be bypassed. In order to receive various services using V2N, it is necessary to go through the authentication process, but if the authentication information is stolen, the service can be used without permission by pretending to be the legitimate authority. In addition, if an appropriate authentication procedure is not in place between the vehicle and the mobile device in a service implementation, an attacker can take advantage of this vulnerability and take control of the vehicle through a mobile device or the like. Repudiation Vulnerability  
Nonrepudiation threats can include extracting private keys and message forgery/ alteration. When a hacker manipulates traffic to impersonate or disguise a specific vehicle or extracts a private key to create and distribute a fake message, it becomes impossible to deny transmission of messages to/from the spoofed vehicle. Conversely, a threat may occur when the fact of message transmission to/from a vehicle is denied. If a message can be forged or altered, it may not be possible to deny that the message was ever sent or received; it may not be possible to grasp a clear meaning when deciding where responsibility lies. In the V2V method, if an attacker manipulates traffic to spoof a specific vehicle, V2I can spoof not only the vehicle but also an RSU, or the attacker can create a false message through the extraction of the private key. A user could arbitrarily change or modify software or hardware in order to use a service through V2N as he/she likes. If an accident occurs, however, that user could deny any operational fact that might be available before the change was made. After restoring the default state, problems such as blaming the manufacturer or the service provider for an accident can occur. In such cases, the manufacturer or service provider must be held liable for the accident, even without negligence, if the user is unable to prove that the system was arbitrarily modified or forged. This can be seen as belonging to the nonrepudiation threat. In addition, there may be a problem with a user not updating software properly. Generally, to repair various bugs and vulnerabilities, service providers send security updates on a regular basis, but users might continue to use systems without updating them. By delaying the update, in the event of damage, the user could hold the service provider responsible for an accident.