Spatial Replay Protection for Proximity Services : Security and privacy aspects

Abstract: Proximity Services is a new feature in the 3rd Generation Partnership Project (3GPP) standard for mobile communication. This features gives the opportunity to provide services locally if the targets are sufficiently close. However, in the current version of the proposed specification, there is no protection against a malicious user tunneling messages to a remote location to give the impression of proximity. This thesis proposes solutions to protect against such a spatial replay attack and evaluates these solutions based on how the user’s integrity is preserved, their complexity, and the added overhead. It is not obvious today what the consequences of a spatial replay attack are and how serious such an attack could be. However, once the feature is deployed and people start using it, it could prove to be a major vulnerability. The methods presented in this thesis could be used to prevent spatial replay in 3GPP or similar standards proximity services. The chosen method is a geographical packet leash based on a poly-cylindrical grid for which only a certain amount of Least Significant Bits of the grid cell identifier is included in the initial Discovery Message and the rest could be used in the calculation of the Message Authentication Code.