Abuse-Resistant Location Tracking: Balancing Privacy and Safety in the Offline Finding Ecosystem

Location tracking accessories (or ``tracking tags\u27\u27) such as those sold by Apple, Samsung, and Tile, allow owners to track the location of their property and devices via offline tracking networks. The tracking protocols have been designed to ensure some level of user privacy against surveillance by the vendor. Such privacy mechanisms, however, seem to be at odds with the phenomenon of tracker-based stalking, where attackers use these very tags to monitor a target\u27s movements. Numerous such criminal incidents have been reported, and in response, manufacturers have chosen to weaken privacy guarantees in order to allow users to detect malicious stalker tags. In this work we show how to achieve an improved trade-off between user privacy and stalker detection within the constraints of existing tracking protocols. We implement our new protocol using families of list-decodable error-correcting codes, and give efficient algorithms for stalker detection under realistic conditions

Fast Decoding of Interleaved Linearized Reed-Solomon Codes and Variants

We construct s-interleaved linearized Reed-Solomon (ILRS) codes and variants and propose efficient decoding schemes that can correct errors beyond the unique decoding radius in the sum-rank, sum-subspace and skew metric. The proposed interpolation-based scheme for ILRS codes can be used as a list decoder or as a probabilistic unique decoder that corrects errors of sum-rank up to $t\leq\frac{s}{s+1}(n-k)$, where s is the interleaving order, n the length and k the dimension of the code. Upper bounds on the list size and the decoding failure probability are given where the latter is based on a novel Loidreau-Overbeck-like decoder for ILRS codes. The results are extended to decoding of lifted interleaved linearized Reed-Solomon (LILRS) codes in the sum-subspace metric and interleaved skew Reed-Solomon (ISRS) codes in the skew metric. We generalize fast minimal approximant basis interpolation techniques to obtain efficient decoding schemes for ILRS codes (and variants) with subquadratic complexity in the code length. Up to our knowledge, the presented decoding schemes are the first being able to correct errors beyond the unique decoding region in the sum-rank, sum-subspace and skew metric. The results for the proposed decoding schemes are validated via Monte Carlo simulations.Comment: submitted to IEEE Transactions on Information Theory, 57 pages, 10 figure