# A Blockchain-Based Framework to Enhance Anonymous Services with Accountability Guarantees
## 8 Conclusions and Discussion  
Anonymous services have shown increasing popularity over the years. However, for most of these services, it is crucial to not just provide anonymity to the user but also to implement an accountability mechanism. In this paper, we propose a blockchain-based approach as a solution to the accountability issue in anonymous services. Our solution requires that only the co-operation of three independent parties (\(IG\), \(LA\), and \(SP\)) can de-anonymize a user who is performing illegally on the \(SP\) platform. This fact represents the main advantage of our solution since it makes an illegitimate attempt to de-anonymize the user unlikely. To prove that our solution can be applied in real-life contexts, we provide a prototype that takes into account usability aspects, as it aims to reduce the number of operations performed client-side. Moreover we provide a time and cost analysis of our solution in order to demonstrate its feasibility. According to our cost analysis, the most expensive operation consists in the smart contract deployment in the Ethereum network (approximately USD 5). However, such an operation is meant to be performed only once by \(IG\), \(LA\), and \(SP\). Hence, it is safe to assume that such a cost is sustainable. The other operation that they have to perform is setChallenge, whose cost is estimated to be USD 0.54. Even though this operation has to be performed for each user willing to subscribe to an anonymous service, its results are acceptable for the service providers. However, in a possible business model, the provider can charge the user for this cost. On the other hand, the cost to perform the solveChallenge operation is an equally low price (USD 0.24) and is meant to be paid directly by the user. Considering instead the cost of a complete user registration (which requires the execution of both setChallenge and solveChallenge), it turns out to be very cheap (around USD 2). It is therefore realistic to assume that this cost can be charged to the user in order to not burden the providers. Regarding the time analysis that we conducted, our study shows that the registration procedure with \(IG\) requires less than 1 min, whereas the registration procedure with \(SP\) and \(LA\) requires less than 2 min. It is worth noting that the time intervals related to the operations involving the blockchain are predominant (ranging from 15 to 25 s). However, despite this tolerable drawback, relying on the blockchain for these operations has the advantage of making them immutable and publicly verifiable. Therefore, untrusted parties (\(IG\), \(LA\), and \(SP\)) cannot hold other users accountable instead of the real misbehaving user. Furthermore, as the entire registration process is one time, the overall time taken to perform a complete registration is reasonable. To conclude, our solution is shown to be usable and reasonably time and cost-efficient. As for the cost, we may argue that honest users might be encouraged to pay for a service that, in addition to anonymity, would guarantee them the possibility of reporting dishonest users who might take advantage of the anonymous service to threaten them. Moreover, the anonymous service provider itself might be encouraged to employ our solution since accountability guarantees can discourage users from engaging in illegal behaviour, thus improving the overall reputation of the anonymous service provider. As a future work, we plan to further increase the technology readiness level of our research by proposing its application to real-life environments, possibly with industrial partners. Conceptualization, F.B., V.D.A. and S.L. ; methodology, F.B., V.D.A. and S.L. ; software, V.D.A. and S.L. ; validation, F.B., V.D.A. and S.L. ; formal analysis, F.B., V.D.A. and S.L. ; investigation, F.B., V.D.A. and S.L. ; resources, V.D.A. and S.L. ; data curation, V.D.A. and S.L. ; writing--original draft preparation, F.B., V.D.A. and S.L. ; writing--review and editing, F.B., V.D.A. and S.L. ; visualization, V.D.A. and S.L. ; supervision, F.B.