A growing trend in today’s society is outsourcing large
databases to the cloud. This permits to move the
management burden from the data owner to external
providers, which can make vast and scalable
infrastructures available at competitive prices. Since
large databases can include sensitive information,
effective protection of data confidentiality is a key issue
to fully enable data owners to enjoy the benefits of
cloud-based solutions. Data encryption and data
fragmentation have been proposed as two natural
solutions for protecting data confidentiality. However,
their adoption does not permit to completely delegate
query evaluation at the provider. In this chapter, we
illustrate some encryption-based and fragmentation-
based solutions for protecting data confidentiality,
discussing also how they support query execution.