Cloud computing offers a few security challenges, including hacking due to misconfigurations or vulnerabilities, as well as complex regulatory and legal issues surrounding data management. Identity and access management in multi-tenant environments increases complexity, as does the potential of data loss due to accidental deletion or criminal activity. Insider threats from workers or outside suppliers amplify these concerns. The shared responsibility model between cloud service providers and clients needs a clear definition of security roles. Also, the availability of malware and advanced persistent threats, combined with differences in security standards across providers, complicates security efforts. Reducing these issues requires a complete plan that includes technical controls, attention to the best security standards, continual monitoring, and regular personnel training. In our work, we are proposing blockchain based decentralized approach for securing a fog computing environment. We have observed the performance of the model in three different scenarios. Results reveal the fact that the proposed model is able to withstand with the attacks and successfully added the candidate block to the existing environment with minimal performance degradation.