Homomorphism is a concept that allows one to perform arbitrary calculations on the cipher text. One of the application of this concept is securing one’s location while one uses location based services(LBS). In this paper I have discussed an approach to preserve mobile user’s location while accessing some location based service. The mobile user is trying to find the nearest locations of his interest using a mobile application. While doing so he wishes to keep his location coordinates a secret from the server. This is because, these days since servers may be maintained by a third party or a middleware might be involved. There is no scope of trusting anyone in this insecure world. Therefore, since in homomorphic encryption offers a way of making calculations on the cipher text thereby not revealing anything about the plaintext to the server, it becomes a more secure and safer choice for making a system which wants to keep the data protected from the server.
Problem Statement: Implementing k-nearest neighbour algorithm while preserving user location privacy using homomorphic encryption.

In 2009 Craig Gentry proved that Fully Homomorphic Encryption can be applied and realized in principle. Homomorphism allowed us to perform arbitrary computations and calculations on encrypted data. With RSA being the first cryptosystem to hold homomorphic properties, there came other additive and multiplicative cryptosystems. However, fully Homomorphic encryption proved to be the ultimate cryptographic solution to ensure security of data on cloud. It enables processing and computing arbitrary functions over the encrypted data thereby reducing the probability of accessing the plain text.