Blind Nearest Neighbor Query Evaluation via Encoded Spatial Transformations
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Solution Overview
Problem
Existing location-based services face challenges in preserving user privacy during K-nearest neighbor and range queries, as they often require revealing location information, which can lead to information leakage and compromise user anonymity and location privacy.
Innovation Solution
The method involves encoding user locations and points of interest into a transformed space using space-filling curves like Hilbert curves, ensuring relative proximity is maintained, and providing encrypted results, with users possessing keys for reverse transformation, thus preventing location information exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If location information is revealed to perform K-nearest neighbor queries, then query accuracy is improved, but user privacy and anonymity are compromised
Solution Approach 1:
The patent introduces a location server as an intermediary that operates in a transformed space rather than directly accessing user locations. The server receives encoded location data, performs queries in the transformed space, and returns encrypted results, thereby mediating between query accuracy requirements and user privacy protection without requiring direct revelation of user locations
Solution Approach 2:
The patent transforms user locations from original coordinate space into a transformed space using space-filling curves (such as Hilbert curves). This parameter transformation preserves spatial relationships while obfuscating actual location data, allowing queries to be performed without revealing user privacy information
2Loss of information
If space transformation is applied to encode locations, then user privacy is protected, but computation complexity increases
Solution Approach 1:
The patent performs space transformation and encoding operations in advance during system initialization or data loading phases. By pre-computing and storing transformed location data and spatial indices, the system reduces computation complexity during actual query processing while maintaining privacy protection
Solution Approach 2:
The patent creates a transformed copy of the spatial data structure (such as a quadtree or grid) where locations are represented in the transformed space rather than original coordinates. This copying approach allows queries to be performed on the transformed data structure without repeatedly performing complex transformation operations
3Reliability
If encoded locations are stored in transformed space, then query results remain encrypted, but access to location data becomes more difficult
Solution Approach 1:
The patent implements a system where only the user who issued the query possesses the decryption key and can access their own location information. The location server cannot decrypt or access user locations, and other users cannot access anyone's location data, creating a self-service model where each user independently manages their own data accessibility
Solution Approach 2:
The patent applies different accessibility qualities to different data: location data is encrypted and inaccessible to servers and other users, while query results are selectively decrypted and accessible only to the querying user. This local quality differentiation ensures security for stored data while maintaining operational ease for authorized access
Data Source
AI summary
Systems and techniques are described for blind evaluation of nearest neighbor queries. Locations of multiple users in an original space are received. The locations in the original space are encoded into encoded locations in a transformed space. A relative proximity of the encoded locations in the transformed space is maintained after the encoding. Multiple keys corresponding to the multiple users are generated. Each key enables a reverse transformation of an encoded user location in the transformed space to an original user location in the original space. The multiple keys are provided to the corresponding multiple users, and the encoded locations in the transformed space are provided to a device. An order of computations required to reverse transform the encoded locations in the transformed space to the locations in the original space in the absence of a key is greater than a computational threshold.