# Trusted Third Party Application in Durable Medium e-Service
## 2 Related Works
According to the authors, the advantage of the approach is that TPA is not able to extract the content of data stored on the cloud server during the audit process, which eliminates potentially costly auditing burdens and alleviates CC fears of data leakage. The trusted third party is also present in many other areas. For example, the combination of TTP and agent systems can help to control the quality-of-service contracts and guarantee transparency and symmetry regarding the service level agreement (SLA) between potential signatories [21]. Research on applying TTP in the management of services in automotive clouds is also very interesting [22]. The authors compare two algorithms: service latency sensitive mode (SLSM) and neutral mode for connecting vehicles to the cloud using TTP to provide services. As a result, delays in connecting vehicles with TTP are smaller (depending on the number of suppliers, vehicles, and available service providers). On the other hand, services such as video and audio have a greater improvement in service latency than \"lighter\" services such as fuel price. From the general point of view, the usage of an open or permissioned blockchain can be effective only in the case of many conjointly mistrusting entities that intend to interact and alter the state of the system. Those entities are not eager to reach an agreement on an online TTP. In such a situation, it is assumed that one or many parties relate to an entity with admittance in a distinctive database structure or to a consensus member in a blockchain architecture. In the case where no data ought to be kept, the database is not obligatory at all; that is, a blockchain-form database is useless. Analogously, in the case where there is only one writer, a blockchain does not make extra guarantees available, and an ordered database is much more suitable as it offers better enactment of throughput and reduces latency. Additionally, if a TTP is applied, there are two possibilities. The first one refers to the TTP that is continuously online. Then, tasks regarding storing data can be passed on to it and it can work as a verifier for state transitions. The second possibility relates to the situation where the TTP is typically offline. It can work as a certificate authority in environments of permissioned blockchain, and all writers of the system are identified. In the scenario where all the writers mutually trust each other, it is considered that no member is malicious. In such a case, the database with shared write authority seems to be the best option. Alternatively, if there is no mutual trust between the writers, the permissioned blockchain is a better option. It is liable if public verifiability is obligatory. Then, anyone can be accepted for reading the state (public permissioned blockchain), or several readers can be limited (private permissioned blockchain). If the number of writers is not static, nor identified to the members (like in the case of many cryptocurrencies, such as Bitcoin), a permissionless blockchain is an appropriate resolution. In the area of cryptocurrencies and blockchain technology, researchers point out the problem of lacking the trust associated with transactions in the Bitcoin network. As these transactions are irreversible, consumers may be wary of entering into them [23]. In [24], interesting research is presented. The authors propose the T\({}^{3}\)AB framework to address the transparency and trustworthiness of third-party authorities (TPAs) and honest-but-curious entities in functional encryption (FE) or attribute-based encryption (ABE)-enabled applications, as well as other schemes that have components similar to TPAs. The framework employs the Ethereum blockchain as the underlying public ledger infrastructure, and incorporates a novel smart contract to support accountability with an additional incentive mechanism that motivates participants to engage in auditing and punish misbehaviors or malicious behaviors in the environment.