The benefits of distributed systems and shared database resources are widely recognized, but they often cannot be exploited by users who must protect their data by using label-based access controls. In particular, users of label-based data need to read and write data at different security levels within a single database transaction, which is not currently possible without violating multilevel security constraints. The paper presents a formal model of multilevel transactions which provide this capability. We define four ACIS (atomicity, consistency, isolation, and security) correctness properties of multilevel transactions. While atomicity, consistency and isolation are mutually achievable in standard single-site and distributed transactions, we show that the security requirements of multilevel transactions conflict with some of these goals. This forces trade-offs to be made among the ACIS correctness properties, and we define appropriate partial correctness properties. Due to such trade-offs, an important problem is to design multilevel transaction execution protocols which achieve the greatest possible degree of correctness. These protocols must provide a variety of approaches to making trade-offs according to the differing priorities of various users. We present three transaction execution protocols which achieve a high degree of correctness. These protocols exemplify the correctness trade-offs proven in the paper, and offer realistic implementation options.

One of the most important responsibilities of a database management system (DBMS) is maintaining the integrity of data. Traditional database integrity mechanisms have evolved in DBMSs to fulfill this need, including transaction management to maintain

Over the last several years, there has been an emphasis on distributed client/server computing in business as well as government. A useful means of achieving this capability is through the use of object technology. Distributed object systems offer many benefits, such as downsizing and right sizing, resulting in a trend toward small, modular, commercial or government off-the-shelf components as a means of system development. Distributed object management standards, such as the Common Object Request Broker Architecture (CORBA) specification are aiding the integration process. One area of distributed object systems that has received little attention to date is security. Security is a difficult problem in traditional software systems, and adding distribution and use of object-oriented techniques just increases the complexity of the problem. The Object Management Group (OMG) is beginning to solicit proposals from vendors for handling security in a distributed object environment. This paper gives an overview of distributed object management and standards being specified by the OMG. It applies traditional security engineering analysis to CORBA and highlights some of the security function interdependencies among CORBA components.>

Data management applications that use multilevel database management system (DBMS) capabilities have the requirement to read and write objects at multiple levels within the bounds of a multilevel transaction. The authors define a new notion of atomicity that is meaningful within the constraints of the multilevel environment. They offer a model of multilevel atomicity that defines varying degrees of atomicity and recognizes that lower security level operations within a transaction must be able to commit or abort independently of higher security level operations. Execution graphs are provided as a tool for analyzing atomicity requirements in conjunction with internal semantic interdependencies among the operations of a transaction and rules for determining the greatest degree of atomicity are proved that can be attained for a given multilevel transaction. Several alternative transaction management algorithms that can be used to preserve multilevel atomicity are presented.>

Examples of DoD/intelligence data protection requirements are described that cannot be handled through traditional mandatory (MAC) or discretionary (DAC) access controls, and two new forms of access controls to respond to these problems are proposed. First, a user attribute-based access control for enforcement of dissemination controls is introduced. Second, a type of access control known as owner-retained access control is described, to provide a privilege-based form of access control that, unlike DAC, prevents access to data being extended to others without the owner's concurrence. For both types of controls, the access control rules to be enforced and the implications of providing automated enforcement of these controls are discussed. The two forms of control are compared, and an informal model is presented that provides a common framework for representing both. In conclusion, the benefits and drawbacks of this approach are discussed, and some areas for future work are identified.>