Web application security: In applications that are oriented
cloud data storage, encryption can be integrated into the
different level of the storage process . First, we find the
server-side encryption where the data are stored encrypted in
the storage servers. In this case, the keys are usually user
independent and are managed by the server owner. The second
level is the data transmission. It is based on the encryption of
the traffic between the client and the server. Some storage
applications use merely the encrypted transmission such as
Google Drive. Others combine it with the server-side encryption,
such as Dropbox. In the case of Dropbox, the connection
between the client and the server is secured with SSLffLS and
the uploaded data are stored in Amazon S3 storage service
encrypted with AES-256 [17]. The last level is the client side.
Thereby, the Cloud is considered as an encrypted blob store.
In this case, all the elements related to the security, such as the
keys and the encryption functions, are managed by the client.
Among the Cloud storage solutions that follow this strategy,
we find Amazon S3, CloudFogger [18] , Amazon S3 with
SafeNet integration and Wuala .