# SoK: Delegated Security in the Internet of Things
## 5 Security Evaluation of Existing Protocols
### Process and Results of Security Evaluation
#### 5.2.2 Authentication Delegation  
In this application domain, the D2 TLS protocol introduced in [22] (see Section 2.2, Figure 4) is examined. According to Definition 4, \(\mathcal{A}_{weak}\) initially receives as an input list \(F\) identified parties which are remotely reachable by \(\mathcal{A}_{weak}\). \(\mathcal{A}_{middle}\) and \(\mathcal{A}_{strong}\) receive as input the access matrix \(M\); hence, they are aware of all participants of the system, and their legitimate access.  
In this application domain, \(\mathcal{A}_{weak}\) is able to query only Del. As \(\mathcal{A}_{weak}\) does not have corruption capability, they cannot compromise any protocol participants in order to obtain their s. Hence, \(\mathcal{A}_{weak}\) cannot be authenticated instead of legitimate clients and tamper with their resources \(\mathcal{R}\). Based on this, the protocol can be proven secure against \(\mathcal{A}_{weak}\) in terms of confidentiality and integrity. Considering the capability of \(\mathcal{A}_{weak}\) to violate the availability property, \(\mathcal{A}_{weak}\) is able to perform DoS attacks against the SA acting as \(\mathcal{D}\) by sending numerous delegation requests. Additionally, DoS attacks against a client during protocol operation can cause its interruption. Therefore, this protocol is not secure against \(\mathcal{A}_{weak}\) regarding availability.  
\(\mathcal{A}_{middle}\) can query not only Del but also Obs. In the given protocol, in order to be successfully authenticated, the adversary should not only have credentials but also be able to forge the client's signature during run time. We assume that this is likely not feasible even within the asymptotic time available for \(\mathcal{A}_{middle}\), and the given protocol is secure against \(\mathcal{A}_{middle}\) in terms of confidentiality. In this scenario, if confidentiality is not violated, integrity is not violated either. Attacks on communication channels, such as man-in-the-middle (MitM), also cannot be successful because the presented protocol employs the DTLS protocol, which is based on the TLS protocol that ensures the confidentiality and integrity of information during transmission. Therefore, this protocol is likely secure against \(\mathcal{A}_{middle}\) in terms of integrity. Availability of the system can be disrupted by performing DoS attacks against SA and clients.  
As the most powerful adversary, insider \(\mathcal{A}_{strong}\) has access to all available oracles (Del, Cor, Obs) and also has unlimited time \(It\). These resources allow \(\mathcal{A}_{strong}\) to perform spoofing, information disclosure, tampering, repudiation, elevation of privilege, and DoS attacks against clients and the SA. Having enough time, \(\mathcal{A}_{strong}\) can spoof a legitimate client and forge its signature in order to perform the authentication process. Also, \(\mathcal{A}_{strong}\) can compromise the SA and manipulate its decisions, violating the confidentiality and integrity of the data and the availability of the system.