Now a days the security demands of data outsourcing applications is increasing and it is becoming an important issue in sustainable smart cities. Client's data which is encrypted has been widely accepted by industry. As the clouds and edges are not far trusted encryption of data should be done at client side and then it should be outsource. Therefore, it is challenging issue that how to correctly encrypt the data so that encrypted and remotely stored data can be queried to get it back. We

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... d that not so much people have worked on approaches for graph -structured data encryption and support for graph queries answering so it is still lacking in studies. In this paper, we investigate one graph encryption method called top-K Nearest Keyword(kNk) searches .it is an important graph query type, several indexes are design to store information which is necessary to answer queries and to maintain the privacy or security about the graph .It may be vertex identifiers, keywords and edges. Our graph encryption methods are secure or not are demonstrated by theoretical proofs and experiments which is done on real-world datasets.