Optimal Re-encryption Strategy for Joins in Encrypted Databases [chapter]

Florian Kerschbaum, Martin Härterich, Patrick Grofig, Mathias Kohler, Andreas Schaad, Axel Schröpfer, Walter Tighzert
2013 Lecture Notes in Computer Science  
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 log n) re-encryptions for n
more » ... s. We show that there can be no algorithm better than O(n log n). 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.
doi:10.1007/978-3-642-39256-6_13 fatcat:lynliha2njcahgoalhaetz3kfq