Abstract: In order to ensure the location privacy of mobile nodes when using location-based services,a mobile privacy protection scheme for location based service(LBS)based on random onion routing is proposed.This scheme integrates random onion routing and hybrid encryption to ensure the privacy of mobile node location and the security of query requests.The mobile node randomly selects several nodes in the network before sending the query request to the LBS server to build an onion path,and forwards the query request along this path in turn until the LBS server receives the message.Then,the LBS sends the query result to the sen-ding node along the reverse direction of the onion path.In order to realize the anonymity of the sending node,the addresses of each layer on the randomly constructed onion path are encrypted with a combination of symmetric encryption and asymmetric encryption.In this way,layers of encryption are used to generate the final onion path.Each hop node in the path can get only its next-hop node.Neither the LBS server nor any relay node in the onion routing path can know which node is the sending node,so that the location privacy of the sending node can be kept.On the other hand,in order to ensure that no third party can get the query request or query result,the sending node first uses a symmetric key to encrypt the query request.Then it uses the public key of the LBS server to encrypt the symmetric key.Finally it attaches the symmetric key ciphertext to the query request ciphertext and send it to the LBS server.The LBS server will also return the encrypted query result.Experimental results show that the average response time of this scheme increases slowly with the increase of the number of nodes in the system.The average response time will not increases sharply with the increase of the number of nodes,which will lead to system paralysis.So the system has good stability and scalability.The onion path is randomly selected which does not depend on a specific node,so the scheme has better robustness.

Key words: Mobile location privacy, Onion routing, Hybrid encryption, Cyber security