  Cloud business intelligence is an increasingly popular choice to deliver
decision support capabilities via elastic, pay-per-use resources. However, data
security issues are one of the top concerns when dealing with sensitive data.
In this pa-per, we propose a novel approach for securing cloud data warehouses
by flexible verifiable secret sharing, fVSS. Secret sharing encrypts and
distributes data over several cloud ser-vice providers, thus enforcing data
privacy and availability. fVSS addresses four shortcomings in existing secret
sharing-based approaches. First, it allows refreshing the data ware-house when
some service providers fail. Second, it allows on-line analysis processing.
Third, it enforces data integrity with the help of both inner and outer
signatures. Fourth, it helps users control the cost of cloud warehousing by
balanc-ing the load among service providers with respect to their pricing
policies. To illustrate fVSS' efficiency, we thoroughly compare it with
existing secret sharing-based approaches with respect to security features,
querying power and data storage and computing costs.
