Preprint No. 96-2
Ahmad Baraani-Dastjerdi, Josef Pieprzyk, and Reihaneh Safavi-Naini
``Security  In Databases: A Survey Study''

ABSTRACT
In this paper, we survey the security of coventional
databases and object-oriented databases that have been reported in the
current literature. This is an area of substantial interest in databases
because (1) the use of databases is becoming very important in today's
enterprises, (2) databases contain information that is a major enterprise
asset. Security concerns, requirements, and problems that arise in the
pursuit of meeting these requirements for security in databases are
illustrated.  We discuss access control issues in databases, and futher
identify some promising research directions.

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Preprint No. 96-3
Ahmad Baraani-Dastjerdi, Josef Pieprzyk, and Reihaneh Safavi-Naini
``A Security Model for  Multi-level Object-Oriented Databases
Based on Views''

ABSTRACT
In this paper, we employ the view model given  by Bertino to
propose a new design approach for a secure multi-level object-oriented
database system. The central idea is to provide the user with a \em
multi-level view \rm derived from a single-level secure object-oriented
database. Hence the database operations performed on the multi-level views
are
decomposed into a set of operations on the single-level objects which can be
implemented on any conventional mandatory security kernel.

We show that this approach allows us to overcome the difficulties of
handling content and context dependent classification, dynamic
classification, and aggregation and inference problems in multi-level
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Preprint No. 96-4
S.M. Sedighi and J.R. Getta
``Optimization of Query Postprocessing in Heterogeneous
Distributed Multidatabase Systems''

ABSTRACT
Query processing in heterogeneous distributed multidatabase systems
requires decomposition of the queries into subqueries independently
computed in the component databases. In the query postprocessing
stage the partial results are integrated into the final answer.

This paper deals with the efficiency of the integration of partial
results obtained from  component database systems. We propose
several optimization techniques based on transformations of data
integration expression. It is shown that hidden dependencies
between the arguments of a data integration expression can be
used for reduction of the size of partial answers. It is proven
that in specific cases a part of the final answer may be computed
even when not all of the partial results are available.
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Preprint No. 96-5
S.M. Sedighi and J.R. Getta
``Query Processing Strategies in Heterogeneous and Distributed
Multidatabase Systems''

ABSTRACT
This paper addresses a problem of efficient query processing
in heterogeneous and distributed multidatabase systems based
on a global data model architecture.  A query submitted to a
global view of the component database systems is decomposed into
a collection of subqueries.  Selection of the best strategy for
processing of subqueries has an important impact on the response
time.  The paper identifies two generic approaches to submission
and computation of subqueries and proposes two algorithms that
provide a near optimal solution.  Moreover a number of optimization
techniques are proposed for integration of the partial results
into the final answer.
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Preprint No. 96-6
J.P. Pieprzyk
``Cryptographic Algorithms: Properties, Design and Analysis''

ABSTRACT
The paper presents an overview of recent developments
in the design of cryptographic algorithms.
A short historical introduction sheds a ray of light
on some events which contributed to the advancement
of cryptology.
Modern cryptology is intimately tied up to
the fundamental Shannon's work on secrecy systems.
First modern cryptographic algorithms (Lucifer and DES)
are discussed in terms of their impact on the
next generation of conventional crypto-algorithms.
Next algebraic structures of both conventional
and conditionally secure crypto-algorithms are
investigated and an account of the results achieved
is provided.
Later provably secure crypto-algorithms are explored
including pseudorandom bit generators, one-way hashing and
pseudorandom functions.
The work concludes with the review of main
results in the design of S-boxes.
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