Abstract: With the continuous proliferation of location-based service applications, indoor positioning technology has become an important foundational technology for location-based services. When users request positioning services from a service provider, protecting users’ location privacy becomes an important issue that needs to be addressed. For scenarios where only specific personnel are allowed to enter and service providers need to collect user access statistics for specific areas in an anonymous state, this paper proposed a three-party protocol that combines an improved spatial Bloom filter with the Paillier encryption algorithm to achieve secure and efficient anonymous statistics on users accessing specific areas. In the protocol, the service provider used multiple Hash functions to generate Bloom filters for each specific area, which were then encrypted and sent to the cloud server. By leveraging the homomorphic properties of the encryption scheme, the cloud server performed the matching operation between the user’s location and the Bloom filter of a specific area, and the service provider obtained secure user access statistics after decryption. Theoretical analysis and experimental results show that, compared with existing secure query schemes, the proposed protocol achieves a lower false positive rate and reduces computational and communication overhead.

Key words: location privacy, Bloom filter, Hash algorithm, Paillier encryption