| Location-based services(LBS)have developed rapidly in recent years and have been closely related to our daily lives.LBS service needs the geographic information submitted by the user is credible.Proof of Location(PoL)provides location proofs for users through third parties,which can ensure the authenticity and credibility of user location.Traditional PoL models are mostly centralized structures,rely on trusted third parties,which facing the risk of single-point failure and the possibility of data tampering.The distributed architecture of PoL has the problem of trusted cooperation between nodes and the hidden danger of collusion.As a distributed ledger technology,blockchain is trustless,open and resistant to tampering,which can effectively solve the problems existing in the traditional PoL model.It is of great significance to study the blockchainbased proof of location.In recent years,the blockchain-based proof of location has attracted the attention of researchers,and some results have been achieved.However,there are still three outstanding problems to be solved in the blockchainbased proof of location:(1)The location of the witness who provides the location proof is not tightly coupled with the blockchain consensus mechanism,also there is a lack of targeted consensus and incentive mechanisms,resulting in high node deployment costs,overlapping coverage areas,and affecting service quality;(2)The distributed architecture makes it difficult to prevent collusion among users,which reducing the credibility of location proofs;(3)The on-chain storage and location verification stages lack effective privacy protection methods,which may lead to privacy leakage.To solve these problems,this paper deeply studies the blockchainbased proof of location,and proposes solutions for key issues such as the security of location data and privacy leakage.The main innovations of the paper are as follows.(1)Aiming at the problem that the witness location and the consensus mechanism are not tightly coupled,a blockchain proof of location model based on location consensus is proposed.First,a hierarchical proof-oflocation model is proposed,including service layer,network layer and blockchain layer.The security requirements of the model are also analyzed.In the service layer,a blockchain-based proof of location protocol is proposed for the generating and verifying of the location proof secure and reliable,which applies hardened derivation and the interactive zeroknowledge proof to provide external trusted location proof service;In the blockchain layer,aiming at the problem of poor service quality caused by repeated node coverage,a blockchain consensus mechanism DPoL based on node location is proposed.Move the direction to reduce the overall model delay and increase the node coverage area.Finally,security analysis and simulation experiments are carried out.The analysis and experimental results show that the proposed model has low latency and can effectively increase the coverage area of witness nodes while maintaining security.(2)Aiming at the problem that user collusion,especially "proverwitness" collusion in location proof which reduces reliability of PoL,a collusion detection method based on Fuzzy Analytic Hierarchy Process(FAHP)is proposed.Different from traditional research,this method utilizes the trustworthiness and traceability of data on the blockchain to perform user-centered spatiotemporal information correlation and analysis on the location proof records stored on the chain to identify collusion attacks.By defining 12 indicators such as node activity and node correlation in the trajectory,the mapping relationship between node information,trajectory information and the credibility of the location proof is calculated,design the credibility based on the user’s spatiotemporal information.Evaluate the algorithm and calculate the credibility score of each location proof to resist "prover-witness" collusion.Simulation results show that the proposed method can effectively evaluate the credibility of the location proof and identify user collusion more accurately.(3)A privacy protection method based on non-interactive zeroknowledge proof is proposed for the privacy leakage problem in storageand verification stage.Firstly,aiming at privacy leakage problem in the storage stage on blockchain,a Merkel hash tree structure is used to construct a PoL-Rollups on-chain privacy proof storage method,which uses the root of the Merkel hash tree to reduce the storage pressure on blockchain while ensuring privacy.Secondly,aiming at leakage problem in the location verification process,a location verification protocol based on non-interactive zero-knowledge proof is proposed.The protocol is constrained by constraints such as spatiotemporal validity verification,PoL signature verification,Merkle tree existence verification,allowing users to flexibly define privacy indicators and levels,and input PoL-Rollups to generate proofs that meet the constraints,then submit the proof to verifier for non-interactive zero-knowledge verification.The experimental results show that our method has low latency and high flexibility with the privacy is protected. |
