In order to perform a join in a deterministically, adjustably encrypted database one has to re-encrypt at least one column. The problem is to select that column that will result in the minimum number of re-encryptions even under an unknown schedule of joins. Naive strategies may perform too many or even infinitely many re-encryptions. We provide two strategies that allow for a much better performance. In particular the asymptotic behavior is O(n 3/2) resp. O(n logn) re-encryptions for n columns. We show that there can be no algorithm better than O(n logn). We further extend our result to element-wise re-encryptions and show experimentally that our algorithm results in the optimal cost in 41% of the cases. © 2013 IFIP International Federation for Information Processing.
CITATION STYLE
Kerschbaum, F., Härterich, M., Grofig, P., Kohler, M., Schaad, A., Schröpfer, A., & Tighzert, W. (2013). Optimal re-encryption strategy for joins in encrypted databases. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 7964 LNCS, pp. 195–210). https://doi.org/10.1007/978-3-642-39256-6_13
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