Video Evidence Preservation: A Blockchain Perspective

Video surveillance has emerged to be a common supervision method for various situations.In case of unexpected emergencies,these supervision data can be used as important evidence in forensic auditing.However,traditional digital evidence preservation systems mostly adopt centralized design.Given that no sufficient storage and computing capacity,it takes longer period of time to verify the integrity and authenticity of the video files.This paper presents a blockchain-based approach that stores video data in a distributed cloud so as to prevent data from being tampered,leveraging the Hash function to encrypt the original files stored in the blockchain.With the timestamp,sequential data strings that are trackable are formed,which can help identify whether the data is tempered in a timely fashion.The system adopts the P2 P internet structure to eliminate the single point failure,increasing the robustness for our system.The forensic evidence is also required to be released in the blockchain.All of these data are available to the users on the internet,which significantly enhances the transparency of the forensic process.First,an analysis is made to clarify different requirements of users in this system.Then,the system framework is built with the help of the Ethereum platform.Second,in order to reduce the delay of uploading raw data,a bandwidth allocation optimization algorithm is introduced to easy the latency of the process.The algorithm takes into account the impact on bandwidth such as the channel transmission error rate,the probability of collision and the lengths of different file.The parameters in the protocol calculate the bandwidth of each node,and the TXOPlimit parameter is used to improve the performance of bandwidth allocation.The Ethereum private chain is set up and smart contract is written to implement the system.Meta Mask,the Ethereum wallet,is used to help with the management of users.Finally,by testing the performance of the system,and analyzing the video digest processing time,system throughput and CPU utilization,the results show that our system is full of efficiency,safe and scalability.The required gas cost is also estimated to deploy the smart contract or call the functions.In doing so,the newly added nodes could participate in the system in a convenient manner.