Reverse-safe data structures for text indexing

Giulia Bernardini, Huiping Chen, Gabriele Fici, Grigorios Loukides, Solon P. Pissis

Research output: Chapter in Book / Report / Conference proceedingConference contributionAcademicpeer-review


We introduce the notion of reverse-safe data structures. These are data structures that prevent the reconstruction of the data they encode (i.e., they cannot be easily reversed). A data structure D is called z-reverse-safe when there exist at least z datasets with the same set of answers as the ones stored by D. The main challenge is to ensure that D stores as many answers to useful queries as possible, is constructed efficiently, and has size close to the size of the original dataset it encodes. Given a text of length n and an integer z, we propose an algorithm which constructs a z-reverse-safe data structure that has size O(n) and answers pattern matching queries of length at most d optimally, where d is maximal for any such z-reverse-safe data structure. The construction algorithm takes O(nω log d) time, where ω is the matrix multiplication exponent. We show that, despite the nω factor, our engineered implementation takes only a few minutes to finish for million-letter texts. We further show that plugging our method in data analysis applications gives insignificant or no data utility loss. Finally, we show how our technique can be extended to support applications under a realistic adversary model.

Original languageEnglish
Title of host publication2020 Proceedings of the Symposium on Algorithm Engineering and Experiments, ALENEX 2020
EditorsGuy Blelloch, Irene Finocchi
PublisherSociety for Industrial and Applied Mathematics Publications
Number of pages15
ISBN (Electronic)9781611976007
Publication statusPublished - 1 Jan 2020
Externally publishedYes
Event2020 Symposium on Algorithm Engineering and Experiments, ALENEX 2020 - Salt Lake City, United States
Duration: 5 Jan 20206 Jan 2020

Publication series

NameProceedings of the Workshop on Algorithm Engineering and Experiments
ISSN (Print)2164-0300


Conference2020 Symposium on Algorithm Engineering and Experiments, ALENEX 2020
Country/TerritoryUnited States
CitySalt Lake City


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