Use of Bloom Filters to convey identity of surveillance targets

Local data offload performed at a small cell is not commercially deployed as a result of lawful interception issues. Previous work has described a solution to address these issues where a local node performs the same lawful interception functions as is done within the mobile core network for traffic that is offloaded at that local node. However, one issue with this solution is how to transfer the identities of those under surveillance to the local node. Passing the actual identities of targets of surveillance could comprise the required secretive nature of the surveillance. Another issue with the original solution is that by examining the traffic through a small cell, an unauthorized person could determine that a user´s traffic is not being locally offloaded; thereby perhaps indicating that person is a target of surveillance. In this paper, we propose the use of Bloom Filters to convey the identities of those subscribers who are the target of surveillance. The solution is presented and an analysis is included to demonstrate the benefits of the solution. This paper demonstrates that the use of the Bloom Filter hides the identities of the subscribers who are under surveillance. As well, the paper demonstrates that the false positives that occur with a Bloom Filter are actually a benefit from a perspective of obfuscating who is the actual target of surveillance.