On the hardness of separation of duties problems for cloud databases

Abstract

Using cloud databases puts confidential data at risk. We apply vertical fragmentation of data tables in order to obtain insensitive data fragments. These fragments can then be hosted in databases at different cloud providers. Under the assumption that the cloud providers do not communicate, we then obtain a separation of duties such that each provider is unable to recombine the original confidential data set. In this paper, we view this separation of duties as an optimization problem. We show that it is a combination of the two famous NP-hard problems bin packing and vertex coloring. We analyze the complexity of the problem in the standard case (when only confidentiality is required) and the extended case (when also utility is a requirement).