# Blockchain for Future Wireless Networks: A Decade Survey
## 2 Background
### Security in Wireless Networks (From 4G to 6G)  
This section highlights network security issues associated with different generations of WN, such as 4G, 5G, and 6G. In WN, a sender can share information via the Internet with the receiver. The Internet has an intricate design principle using network devices such as routers, switches, hubs, and cables, connected with simple topologies without a stronger security mechanism. This entices the attackers to scan the network devices and interfaces to find potential vulnerabilities which can further be exploited for their own benefit [32; 33]. Figure 2: Organization of the paper. Thus, security and privacy play an essential role in protecting user data in the wireless medium [34]. To overcome that, security specialists have proposed several design factors that pave the way in thwarting the malicious attempts of the attackers. Figure 3 shows the design factors, such as authorization, authentication, encryption, intercept probability, and channel characteristics, that confront the security attacks and improve the reliability of the WN communication. A summarized explanation of each design factor is given as follows. * Authentication--A standard example of WN is the internet, where tons of internet services serve the end users. A sender sends confidential information from these services to the receiver, which in return, the sender expects that the information reaches the correct receiver. Thus, before sending the data, both users have to authenticate themselves for reliable communication. Formally, authentication states that a user has to validate who he/she claims to be with the help of authentication factors, such as a strong password, personal identification number (PIN), one-time password (OTP), and biometrics. However, the attackers can attack the single layer authentication; for example, a password can be cracked using dictionary attacks, OTP can be brute-forced, and biometrics can be manipulated using masterprints or techniques, such as image processing, which generates similar finger prints of the authentic user. Therefore, multi-layer authentication systems are adopted by several organizations to secure their sensitive resources and provide seamless services to the users without any security hindrances. * Authorization--Once the user in the public internet is authenticated, he/she can utilize various internet applications. However, from the security perspective, an attacker can impersonate the authentic user to maliciously read and write confidential information of the validated user or may use the services that are not meant for him. Therefore, there is a need to regulate access control mechanisms after authenticating the user, permitting only authorized users to access the system's services and resources. For that, the administrator has to assign roles and permission to the legitimate user in the access control list. For example, a person can authenticate himself by inserting a username and password into the website; once authenticated, based on the roles and permission assigned, he can access or deny the further services in the website. This helps in poising the security and privacy of the WN-based application. * Encryption--Authentication and authorization help in preserving the privacy of the system. For instance, a web application utilizes the WN to transmit messages from one user to another. One can guarantee that the users who are enrolled with the application are authenticated and authorized to use this service. This is because they are validated and verified by the authentication scheme and authorization mechanism prior to using this application. Nevertheless, the security is violated when the message is in transit; an adversary can access the transit message and try to manipulate it, disobeying the data integrity principles. Therefore, there is a need for incorporating proper encryption standards that obfuscate the message in a way that is not readable by the attackers.