  Data encryption limits the power and efficiency of queries. Direct processing
of encrypted data should ideally be possible to avoid the need for data
decryption, processing, and re-encryption. It is vital to keep the data
searchable and sortable. That is, some information is intentionally leaked.
This intentional leakage technology is known as "querying over encrypted data
schemes", which offer confidentiality as well as querying over encrypted data,
but it is not meant to provide flexible access control. This paper suggests the
use of Ciphertext Policy Attributes Based Encryption (CP-ABE) to address three
security requirements, namely: confidentiality, queries over encrypted data,
and flexible access control. By combining flexible access control and data
confidentiality, CP-ABE can authenticate who can access data and possess the
secret key. Thus, this paper identifies how much data leakage there is in order
to figure out what kinds of operations are allowed when data is encrypted by
CP-ABE.
