# UAV-Based Privacy-Preserved Trustworthy Seamless Service Agility for NextG Cellular Networks
## 2 Related Work
### 5G Security Standard  
The NextG dynamic and highly connected architecture opened the door for several security vulnerabilities, especially with the integration of easily exploited devices such as UAVs. Therefore, an extended security surge is vital to mitigate any malicious attack on the cellular network. The current 5G standard embraces enhanced security protocols that match the new structure to ensure confidentiality, integrity, and authentication [17; 18]. The current 5G authentication protocols relies on a service-based architecture (SBA) known as Authentication and Key Agreement (AKA) to accommodate the 5G service-based structure. The AKA protocol enables key agreement and authentication between the subscribers, the Serving Networks (SNs) that have nearby base stations, and Home Networks (HNs) that corresponds to the subscribers' carriers [19; 20].  
Additionally, UAVs deployment increases security risks as a vulnerable target due to its limited resources and low-security devices. Nevertheless, any attempt to over equip the UAV with traditional security, and authentication protocols can overwhelm the UAV's processor and increase battery draining. Therefore, recent UAV security research works are targeting designing lightweight authentication protocols that will not burden the UAVs. For instance, the authors in [21] proposed a two-stage mutual authentication protocol for Software-Defined Network (SDN)-based multi UAV networks operating in surveillance areas.One of the most recent works is [22], the authors proposed a lightweight Physical Unclonable Function (PUF)-based mutual authentication scheme for UAV flying base station in a 5G network. The authentication in [22] achieves secure authentication without the use of a Public Key Infrastructure (PKI) or any time-consuming encryption. However, the scheme assumes a trusted 5G infrastructure and does not take into consideration mutual authentication. In [23], the authors proposed a lightweight privacy-preserving mutual authentication scheme for UAVs and end-user in WiFi ad hoc networks. The proposed authentication scheme in [23] provides a low computation and communication authentication processing while preserving end-user privacy compared to prior works. However, that protocol adds a large number of communication message toward the gateway node, which will add to the backhaul traffic in the case of cellular networks.  
Proxy signature as a delegation-based algorithm is also an adequate authentication technique for UAVs lightweight authentication. It can provide data security without bringing any extra computational loads to the UAV. Therefore, some recent work utilized proxy signature as an authentication protocol for limited-resource devices such as sensors and UAVs. There have been multiple works that recite different proxy signature approaches for various purposes [24; 25; 26]. For instance, in [27], where the authors proposed a blind ID elliptic Elliptic Curve Cryptography (ECC)-based for UAV network based on Mobile Edge Communication (MEC), while the blind proxy signature is an effective digital signature mechanism, it does not contain any information on the signature's proxy signer (UAV), which increases identity theft attacks [28].  
In [29], the authors proposed a low computational cost short certificate proxy signature for UAV authentication to overcome the integrity attacks on vehicular networks. That certificate-based proxy signature is based on [PERSON], [PERSON], [PERSON] (KPW)'s proxy signature scheme [30], where a proxy key pair depends on the signer's private key for authentic information on the proxy signer's identity. Hence, we utilize [PERSON], [PERSON], and [PERSON]'s proxy signature scheme as a part of our digital signature in our mutual authentication protocol.