# Blockchain-Based Licensed Spectrum Fair Distribution Method towards 6G-Envisioned Communications
## 3 BEAST System Model
### System Process
However, the practical landscape is often marred by self-interested entities that prioritize their personal gains, potentially undermining the welfare of other stakeholders. In the ensuing discussion, we delve into two distinct but concerning attack vectors: overbooking attacks and repudiation attacks, respectively orchestrated with malicious PBS and MNOs. Subsequently, we present compelling proof demonstrating our system's resilience against these adversarial maneuvers. **Definition 1**. : _Ensuring Security against Overbooking Attacks._

Assume the presence of an adversary denoted as \(\mathcal{A}\), endowed with control over a set of available spectrum resources, \(SR_{A}\), within a defined geographical area, \(SA\). Concurrently, we have honest PBS and PUs that have articulated their spectrum requirements, therebyestablishing a spectrum demand set, \(SR_{P}\). We declare that \(\mathcal{A}\) has successfully executed an overbooking attack if, during any stage of system execution, a subset of demands, \(SR^{\prime}\), extracted from \(SR_{P}\), is deceitfully deemed as satisfactorily fulfilled, and significantly, the cardinality of \(SR^{\prime}\) surpasses that of \(SR_{A}\). We assert that a system can effectively thwart \(\mathcal{A}\)'s overbooking attacks if the probability of their successful execution is insubstantial and negligible. This formal articulation encapsulates our commitment to fortify a system against overbooking attacks. By stipulating conditions that deter the illicit expansion of resource allocations with adversarial agents, we ensure the equitable distribution of spectrum resources to legitimate users, precluding any undue advantages from being exploited. Our comprehensive defense strategy effectively safeguards against overbooking attacks through a meticulous amalgamation of the following technologies: blockchain, digital signatures and public key encryption. This harmonious blend forms a potent one-shot solution that guarantees a system's resilience against the insidious overbooking menace. We will now delve into the intricate workings of this defense mechanism, expounding upon the intricate interplay of these components and elucidating how they collectively form an impregnable barrier. The crux of our approach hinges upon a fundamental protocol that mandates each MNO to proactively publish authorization information tailored for the intended PBS or PU beneficiary. This authorization information, crucial for delineating resource access rights, is meticulously endorsed with a digital signature, which is subsequently embedded within the unalterable fabric of the blockchain. In this context, the blockchain stands as an immutable ledger, a distributed network of trust where every participant's contribution is validated with the majority. Herein lies the first line of defense. A potential attacker's capability to tamper with this transcript of authorization information is severely restricted. The steadfast integrity of the blockchain rests upon the collective honesty of the majority of its validators. Thus, the attacker's capacity to manipulate the information is negated by the robustness of this decentralized consensus. The second layer of defense materializes through the indomitable unforgeability of digital signatures. These cryptographic seals unequivocally link each authorization entry to a specific MNO, establishing an incontrovertible connection between the sender and the content. Any attempt to counterfeit or fabricate this signature, a herculean endeavor, is met with insurmountable cryptographic barriers. As such, the authenticity of the transcript is unassailable, preserving the sanctity of the authorization process. A convergence of these elements culminates in the crystallization of the transcript as irrefutable evidence of rendered services. This transcript holds not merely a testament of authorization, but an immutable record of service provisioning, indelibly inscribed in the blockchain's annals.