  In past years, cloud storage systems saw an enormous rise in usage. However,
despite their popularity and importance as underlying infrastructure for more
complex cloud services, today's cloud storage systems do not account for
compliance with regulatory, organizational, or contractual data handling
requirements by design. Since legislation increasingly responds to rising data
protection and privacy concerns, complying with data handling requirements
becomes a crucial property for cloud storage systems. We present PRADA, a
practical approach to account for compliance with data handling requirements in
key-value based cloud storage systems. To achieve this goal, PRADA introduces a
transparent data handling layer, which empowers clients to request specific
data handling requirements and enables operators of cloud storage systems to
comply with them. We implement PRADA on top of the distributed database
Cassandra and show in our evaluation that complying with data handling
requirements in cloud storage systems is practical in real-world cloud
deployments as used for microblogging, data sharing in the Internet of Things,
and distributed email storage.
