Military Communications and Information Technology: A Trusted ...

444 Military Communications and Information Technology...
The data is assumed to be stored in the “cloud”, i.e. somewhere else than where
the actual creators, modifiers, viewers and removers of the data reside. This cloud
has several storage providers, which collectively are assumed to have the following
properties:
The cloud focuses on availability, and there is always one “clean” copy of a desired
document available (after some time or a number of checks). The cloud is not
able to discern between clean and corrupted documents. The cloud is also able to
push authorized changes to a document eventually to other copies throughout its
sphere of influence
Figure 2. Environment for the CBIS documents
The roles related to handling of data are as follows:
• Data Owner is responsible for the data and decides the access control policy
and approves its change policy. Each document has a unique owner, who
controls all the sub-elements of the document.
• Users are the “consumers” of the data blob. A User has READ- and/or
WRITE-permissions to a set of element. If the user has READ-permissions,
she is able to decrypt the content; if she has WRITE-permissions, her edits
can be considered valid via her digital signature. Some users can act on
the behalf of the Owner, and have ADMIN-permissions (permissions to
order changes to the permissions from the Filter)
• Storage is one element in the cloud where the documents physically may
reside. Storage servers are not trusted to view or modify (including filtering
and other reference monitor duties) content, but they are trusted to handle