With the greatly increased use of electronic media for processing and
storing data, data security became an important practical issue. This is
especially true for the extensively shared and distributed systems which
are more and more being accepted in commercial operations. Essen-
tially, the problem is that of protecting data, including all the impli-
cations which this has to the end user as well as the systems or
database designer. However, usually the term data security refers to
protection by technical, i.e., computer science specific, means; if one
wants to in- clude issues such as physical security, how to select the
group of people who should have authority to perform certain operations,
etc., the term computer security is more appropriate. The object of this
book is to provide technical solutions to (facets of) the problem of
achieving data security. The reader who hopes to find clever recipes
which allow circumventing protection mechanisms will, however, be sadly
disappointed. In fact, we deliberately kept the presentation of the
material at a fairly general level. While the short- term benefit of
such an approach may be somewhat smaller, we feel that without a
thorough understanding of the fundamental issues and problems in data
security there will never be secure systems. True, peo- ple probably
always considered certain security aspects when designing a system.
However, an integrated approach is absolutely imperative.