These papers are unpublished, seminal works in computer security. They are papers every serious student of computer security should read. They are not easy to find. The goal of this collection is to make them widely available.
All papers are stored in Adobe's PDF (Portable Document Format). You need a PDF reader to read them. You can get one free of charge at Adobe's web site; click on the icon there marked "Get Acrobat Reader." The documents were produced with Adobe Acrobat version 3.0.
If you have a web browser you can use this interface to access the papers. If you want to see the PDF description, look at the file called Overview.pdf.
Paper descriptions are in the file Papers.pdf. That file is searchable. The papers themselves are not searchable. They are images, not text.
A copy of these instructions is in the text file README.txt.
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Click on the citation to read a description of the importance of the paper; click on the file to read the paper itself.
|ande72.pdf||James P. Anderson, Computer Security Technology Planning Study, ESD-TR-73-51, ESD/AFSC, Hanscom AFB, Bedford, MA 01731 (Oct. 1972) [NTIS AD-758 206]|
|ande80.pdf||James P. Anderson, Computer Security Threat Monitoring and Surveillance, James P. Anderson Co., Fort Washington, PA (Apr. 1980)|
|bell76.pdf||David E. Bell and Leonard La Padula, Secure Computer System: Unified Exposition and Multics Interpretation, ESD-TR-75-306, ESD/AFSC, Hanscom AFB, Bedford, MA 01731 (1975) [DTIC AD-A023588]|
|bisb78.pdf||Richard Bisbey II and Dennis Hollingworth, Protection Analysis: Final Report, ISI/SR-78-13, USC/Information Sciences Institute, Marina Del Rey, CA 90291 Marina Del Rey, CA 90291 (May 1978)|
|dod85.pdf||Department of Defense, Trusted Computer System Evaluation Criteria (Orange Book), DoD 5200.28-STD (1983, 1985)|
|ford78.pdf||Ford Aerospace, Secure Minicomputer Operating System (KSOS): Executive Summary Phase I: Design, Western Development Labratories Division, Palo Alto, CA 94303 (April 1978)|
|karg74.pdf||Paul A. Karger and Roger R. Schell, MULTICS Security Evaluation: Vulnerability Analysis, ESD-TR-74-193 Vol. II, ESD/AFSC, Hanscom AFB, Bedford, MA 01731 (June 1974).|
|lind76.pdf||Theodore A. Linden, Operating System Structures to Support Security and Reliable Software, NBS Technical Note 919, Institute for Computer Sciences and Technology, National Bureau of Standards, US Department of Commerce, Washington DC 20234 (Aug. 1976)|
|myer80.pdf||Philip Myers, Subversion: The Neglected Aspect of Computer Security, Master Thesis. Naval Postgraduate School, Monterey, CA 93940 (June 1980)|
|neum75.pdf||Peter G. Neumann, L. Robinson, Karl N. Levitt, R. S. Boyer, and A. R. Saxena, A Provably Secure Operating System, M79-225, Stanford Research Institute, Menlo Park, CA 94025 (June 1975)|
|niba79.pdf||Grace H. Nibaldi, Proposed Technical Evaluation Criteria for Trusted Computer Systems, M79-225, The Mitre Corporation, Bedford, MA 01730 (Oct. 1979)|
|scha75.pdf||J. M. Schacht, Jobstream Separator System Design, MTR-3022 Vol. 1, The MITRE Corporation, Bedford, MA 01730 (May 1975).|
|sche73.pdf||Roger R. Schell, Peter J. Downey, and Gerald J. Popek, Preliminary Notes on the Design of Secure Military Computer Systems, MCI-73-1, ESD/AFSC, Hanscom AFB, Bedford, MA 01731 (Jan. 1973)|
|schi75.pdf||W. L. Schiller, The Design and Specification of a Security Kernel for the PDP-11/45, MTR-2934, The MITRE Corporation, Bedford, MA 01730 (Mar. 1975)|
|ware70.pdf||Willis Ware, Security Controls for Computer Systems (U): Report of Defense Science Board Task Force on Computer Security; Rand Report R609-1, The RAND Corporation, Santa Monica, CA (Feb. 1970)|
|whit74.pdf||J. Whitmore, A. Bensoussan, P. Green, D. Hunt, A. Robziar, and J. Stern, Design for MULTICS Security Enhancements, ESD-TR-74-176, ESD/AFSC, Hanscom AFB, Bedford, MA 01731 (Dec. 1973).|
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Computer security as a discipline was first studied in the early 1970s, although the issues had influenced the development of many earlier systems such as the Atlas system and MULTICS. Unfortunately, many of the early seminal papers are often overlooked as developers (and sometimes researchers) rediscover problems and solutions, leading to wasted time and development effort.
The information in these papers provides a historical record of how computer security developed, and why. It provides a resource for computer security education. Instructors will be able to assign sets of papers for students to analyze without having to assemble the resource materials. Lastly, it provides a resource for practitioners, to which they can turn to see what has been suggested (and tried) before, under what conditions, and with what results.
During a discussion of this problem and the benefits of studying the papers, someone suggested finding these papers and making them available to the community. This project grew from that idea.
This CD-ROM, the first in a series (we hope), contains 16 seminal papers. Only papers without copyright restrictions were considered, because we wanted to put out the first CD-ROM quickly to enable the community to accrue benefits as early as possible. We also needed to determine if the process were feasible. (as proof that the idea of the project has merit).
To determine which papers should be included, we polled 25 security researchers, developers, and educators who were very familiar with the literature of the period in question. We confined our request to those papers produced under government contract and not published in a journal or conference proceeding. The response was overwhelming. We produced a list of 26 papers that respondents believed should be included.
We then gathered as many of the papers as we could find. Many of the polled people sent us copies of the papers. We were able to obtain, and scan in, 16 for this first release.
For the future: we have numerous papers that we did not put onto the CD-ROM for various reasons, and are still receiving suggestions! We have enough suggestions to produce at least 3 more CD-ROMs. We will attempt to do so in the near future.
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We thank Dr. Blaine Burnham of the NSA for his foresight, encouragement and support. Without it, this project would not have gotten off the ground. We thank Dr. John Gannon of the University of Maryland for his support. It was his contract that supplied the money to collect the papers and scan them into CD-ROM format. We thank James P. Anderson for his patience, knowledge, and immeasurable contributions to this project; Jim donated his collection of papers (which filled six boxes!). Last but not least, we thank Dr. Stuart Katzke of the National Institutes of Science and Technology for his generous support in reproducing these CD-ROMs.
In the early days of computer security, virtually all of the important papers were produced under government contract. Since they were reports rather papers presented at conferences, the authors distributed papers to their colleagues. This meant the reports were not widely disseminated among the general computing community. We focused on these reports because they are seminal and are free from any copyright difficulties. We began with the list in Dr. T. M. P. Lees "Lost Treasures of Computer Security" paper. We might have come up with the same list on our own, but Teds effort saved us much time and discussion. We added our own preferences, and solicited suggestions from about 25 practitioners familiar with the unpublished literature of the early days of computer security. The response to the solicitation was overwhelming, and many of the respondents offered copies of papers they had helped produce, or pointed us to other reports and sources.
We thank the many people at UC Davis who helped scan the papers and produce the CD-ROM, in particular Dr. Chris Wee, David OBrien, Anna Mell, and Michael Fitzgerald. We thank Professor Karl Levitt for his help and support as well.
Computer Security Laboratory
Department of Computer Science
University of California at Davis
One Shields Avenue
Davis, CA 95616-8562
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James P. Anderson, Computer Security Technology Planning Study Volume II, ESD-TR-73-51, Vol. II, Electronic Systems Division, Air Force Systems Command, Hanscom Field, Bedford, MA 01730 (Oct. 1972).
audit, log, surveillance, monitoring, variation, intrusion detection
Details of a planning study for USAF computer security requirements are presented. An Advanced development and Engineering program to obtain an open-use, multilevel secure computing capability is described. Plans are also presented for the related developments of communications security products and the interim solution to present secure computing problems. Finally a Exploratory development plan complementary to the recommended Advanced and Engineering development plans is also included.
James P. Anderson, Computer Security Threat Monitoring and Surveillance, James P. Anderson Co, Fort Washington, PA (1980).
audit, log, surveillance, monitoring, variation, intrusion detection
This is the final report of a study, the purpose of which was to improve the computer security auditing and surveillance capability of the customer's systems.
Audit trails are taken by the customer on a relatively long term (weekly or monthly) basis. This data is accumulated in conjunction with normal systems accounting programs. The audit data is derived from SMF records collected daily from all machines in the main and Special Center. The data is temporarily consolidated into a single file ("dump" data set) from which the various summary accounting and audit trail reports are produced. After the various reports are generated, the entire daily collection of data is transferred to tape. Several years of raw accounting data from all systems are kept in this medium.
Audit trail data is distributed to a variety of individuals for review: a DAC for GIMS applications, activity security officers for some applications located under their purview, but the majority to the customers data processing personnel! For the most part the users and sponsors of a data base or an application are not the recipients of security audit trail data.
Security audit trails can play an important role in the security program for a computer system. As they are presently structured, they are useful primarily in detecting unauthorized access to files. The currently collected customer audit trails are designed to detect unauthorized access to a dataset by user identifiers. However, it is evident that such audit trails are not complete. Users (particularly ODP "personnel" with direct programming access to datasets) may operate at a level of control that bypasses the application level auditing and access controls. In other systems, particularly data management systems, the normal mode of access is expected to be interactive. Programmers with the ability to use access method primitives can frequently access database files directly without leaving any trace in the application access control and audit logs. Under the circumstances, such audit trail concepts can do little more than attempt to detect frontal attacks on some system resource.
Security audit trails can play an important role in a security program for a computer system. As audit trails are presently structured on most machines, they are only useful primarily in detecting unauthorized access to files. For those computers which have no access control mechanisms built into the primary operating systems, the audit trail bears the burden of detecting unauthorized access to system resources. As access control mechanisms are installed in the operating systems, the need for security audit trail data will be even greater: it will not only be able to record attempted unauthorized access, but will be virtually the only method by which user actions which are authorized but excessive can be detected.
In computer installations in general, security audit trails, if taken, are rarely complete and almost never geared to the needs of the security officers whose responsibility it is to protect ADP assets. The balance of this report outlines the considerations and general design of a system which provides an initial set of tools to computer system security officers for use in their jobs. The discussion does not suggest the elimination of any existing security audit data collection and distribution. Rather it suggests augmenting any such schemes with information for the security personnel directly involved.
David E. Bell and Leonard J. LaPadula, Secure Computer System: Unified Exposition and MULTICS Interpretation, MTR-2997 Rev. 1, The MITRE Corporation, Bedford, MA 01730 (Mar. 1976); also ESD-TR-75-306, rev. 1, Electronic Systems Division, Air Force Systems Command, Hanscom Field, Bedford, MA 01731.
security policy, model simple security condition, star property, asterisk-property, mathematical model, secure computer system, security, trusted subject
For the past several years ESD has been involved in various projects relating to secure computer systems design and operation. One of the continuing efforts, started in 1972 at MITRE, has been secure computer system modeling. The effort initially produced a mathematical framework and a model [1, 2] and subsequently developed refinements and extensions to the model  which reflected a computer system architecture similar to that of Multics . Recently a large effort has been proceeding to produce a design for a secure Multics based on the mathematical model given in [l, 2, 3].
Any attempt to use the model, whose documentation existed in three separate reports until this document was produced, would have been hampered by the lack of a single, consistent reference. Another problem for designers is the difficulty of relating the abstract entities of the model to the real entities of the Multics system. These two problems are solved by this document.
All significant material to date on the mathematical model has been collected in one place in the Appendix of this report. A number of minor changes have been incorporated, most of them notational or stylistic , in order to provide a uniform, consistent, and easy-to-read reference. A substantive difference between the model of the Appendix and that of the references [2, 3] is the set of rules: the specific rules presented in Appendix have been adapted to the evolving Multics security kernel design.
Because the model is by nature abstract and, therefore, not understandable in one easy reading, Section II gives a prose description of the model.
In order to relate the mathematical model to the Multics design, Section III exhibits correspondences from Multics and security kernel entities to model entities.
Section IV discusses further considerations--topics which lie outside the scope of the current model but which are important issues for security kernel design.
As background for the remainder of this document, we briefly establish a general framework of related efforts in the rest of this section.
Work on secure computer systems, in one aspect or another, has been reported fairly continuously since the mid 1960s. Three periods are discernible: early history, transitional history, and current events.
The work by Weissmann  on the ADEPT-50 system stands out in the early history period. Not only was a fairly formal structuring of solution to a security problem provided, but ADEPT-50 was actually built and operated. In this early period the work of Lampson  is most representative of attempts to attack security problems rigorously through a formal medium of expression. In Lampson's work, the problem of access control is formulated very abstractly for the first time, using the concepts of "subjects," "object," and "access matrix." The early period, which ended in 1972, understandably did not provide a complete and demonstrable mathematical formulation of a solution.
The transitional period (1972 - 1974) is characterized by markedly increased interest in computer security issues as evidenced by the Anderson panel . One of the principal results of this panel was the characterization of a solution to the problem of secure computing (using the concept of a "reference monitor") together with the reasoned dictum that comprehensive and rigorous modeling is intrinsic to a solution to the problem. This period also saw the development of the first demonstrated mathematical models [l, 2, 13] as well as ancillary mathematical results which characterized the nature of the correctness proof demonstration [2, 8]. A second modeling effort, also sponsored by the Electronic Systems Division of the United States Air Force and performed at Case-Western Reserve University, was also undertaken in this period . In this model, the flow of information between repositories was investigated, initially in a static environment (that is, one in which neither creation nor deletion of agents or repositories is allowed) and subsequently in a dynamic environment. Many other papers appeared during this period. An implementation of a system based on a mathematical model was carried out at MITRE by W. L. Schiller . An extension and refinement of the first model was developed  to tailor the model to the exigencies of a proposed Multics implementation of the model; included in this extension was a concept promulgated at Case-Western Reserve concerning compatibility between the Multics directory structure and the classifications of the individual files. A great number of other computer security issues were investigated and characterized [11, 12, 13, 14, 15] during this time.
Current work succeeding the work reported above is a project sponsored by ESD and ARPA. In this project, the Air Force, the MITRE Corporation, and Honeywell are working cooperatively to develop a design for a security kernel for the Honeywell Multics (HIS level 68) computer system. Other significant efforts include work at UCLA , and the Stanford Research Institute .
This report summarizes, both narratively and formally, the particular version of the mathematical model that is relevant to the development of a Multics security kernel. The report not only presents the model in convenient and readable form, but also explicitly relates the model to the emerging Multics kernel design to help bridge the gap between the mathematical notions of the model and their counterparts in the Multics security kernel.
Richard Bisbey II and Dennis Hollingworth, Protection Analysis: Final Report, ISI/SR-78-13, University of Southern California/Information Sciences Institute, Marina Del Rey, CA 96291 (May 1978).
vulnerability, penetration, access control, error analysis, error-driven evaluation, error type, operating system security, protection evaluation, protection policy, software security
The Protection Analysis project was initiated at ISI by ARPA IPTO to further understand operating system security vulnerabilities and, where possible, identify automatable techniques for detecting such vulnerabilities in existing system software. The primary goal of the project was to make protection evaluation both more effective and more economical by decomposing it into more manageable and methodical subtasks so as to drastically reduce the requirement for protection expertise and make it as independent as possible of the skills and motivation of the actual individuals involved. The project focused on near-term solutions to the problem of improving the security of existing and future operating systems in an attempt to have some impact on the security of the systems which would be in use over the next ten years.
A general strategy was identified, referred to as "pattern-directed protection evaluation" and tailored to the problem of evaluating existing systems. The approach provided a basis for categorizing protection errors according to their security-relevant properties; it was successfully applied for one such category to the MULTICS operating system, resulting in the detection of previously unknown security vulnerabilities.
Department of Defense, Trusted Computer System Evaluation Criteria, DoD 5200.28-STD, National Computer Security Center, Ft. Meade, MD 20755 (Dec. 1985). Also known as the "Orange Book."
Standard, trusted system, evaluation, Orange Book, protection, class, security requirement
The trusted computer system evaluation criteria defined in this document classify systems into four broad hierarchical divisions of enhanced security protection. They provide a basis for the evaluation of effectiveness of security controls built into automatic data processing system products. The criteria were developed with three objectives in mind: (a) to provide users with a yardstick with which to assess the degree of trust that can be placed in computer systems for the secure processing of classified or other sensitive information; (b) to provide guidance to manufacturers as to what to build into their new, widely-available trusted commercial products in order to satisfy trust requirements for sensitive applications; and (c) to provide a basis for specifying security requirements in acquisition specifications. Two types of requirements are delineated for secure processing: (a) specific security feature requirements and (b) assurance requirements. Some of the latter requirements enable evaluation personnel to determine if the required features are present and functioning as intended. The scope of these criteria is to be applied to the set of components comprising a trusted system, and is not necessarily to be applied to each system component individually. Hence, some components of a system may be completely untrusted, while others may be individually evaluated to a lower or higher evaluation class than the trusted product considered as a whole system. In trusted products at the high end of the range, the strength of the reference monitor is such that most of the components can be completely untrusted. Though the criteria are intended to be application-independent, the specific security feature requirements may have to be interpreted when applying the criteria to specific systems with their own functional requirements, applications or special environments (e.g., communications processors, process control computers, and embedded systems in general). The underlying assurance requirements can be applied across the entire spectrum of ADP system or application processing environments without special interpretation.
Ford Aerospace and Communications Corporation, Secure Minicomputer Operating System (KSOS) Executive Summary: Phase I: Design of the Department of Defense Kernelized Secure Operating System, WDL-781, Palo Alto, CA 94303 (Mar. 1978).
trusted system, UNIX, formal specification, multilevel, security kernel, KSOS
The long-term goal of the KSOS effort is to develop a commercially viable computer operating system for the DEC PDP-11/70 that
In order to achieve this goal, the Phase I effort described here has designed a trusted Security Kernel and associated trusted Non-Kernel Security-Related Software, such that the trusted software:
The security of the overall KSOS system must be convincingly demonstrated. This will be accomplished by formal verification of the security properties of the design (i.e., the formal specifications) and selected proofs of correspondence between the delivered code and the design. In addition, KSOS will be rigorously tested to lend added confidence in the in the system.
Although the Security Kernel is intended initially to support an Emulator providing a UNIX*tm-like user environment, the Kernel has been designed to be used by itself, or with an Emulator providing a different user environment. Typical uses of the Kernel by itself would be dedicated secure systems such as military message processing systems, or secure network front ends.
Paul A. Karger and Roger R. Schell, MULTICS Security Evaluation, Volume II: Vulnerability Analysis, ESD-TR-74-193, Vol. II, Electronic Systems Division, Air Force Systems Command, Hanscom Field, Bedford, MA 01731 (June 1974).
access control, multi-level system, operating system vulnerability, privacy, monitor, secure computer system, security kernel, penetration, security testing, segmentation
A security evaluation of Multics for potential use as a two-level (Secret/Top Secret) system in the Air Force Data Services Center (AFDSC) is presented. An overview is provided of the present implementation of the Multics Security controls. The report then details the results of a penetration exercise of Multics on the HIS 645 computer. In addition, preliminary results of a penetration exercise of Multics on the new HIS 6180 computer are presented. The report concludes that Multics as implemented today is not certifiably secure and cannot be used in an open use multi-level system- However, the Multics security design principles are significantly better than other contemporary systems. Thus, Multics as implemented today, can be used in a benign Secret/Top Secret environment . In addition, Multics forms a base from which a certifiably secure open use multi-level system can be developed.
Theodore Linden, Operating System Structures to Support Security and Reliable Software NBS Technical Note 919, Institute for Computer Sciences and Technology, National Bureau of Standards, Department of Commerce, Washington DC 20234 (Aug. 1976).
capability, capability-based addressing, extended-type objects, operating system structures, protection, reliable software, reliability, security, small protection domains, types.
Security has become an important and challenging goal in the design of computer systems. This survey focuses on two system structuring concepts that support security; namely, small protection domains and extended-type objects. These two concepts are especially promising because they also support reliable software by encouraging and enforcing highly modular software structures--in both systems software and in applications programs. Small protection domains allow each subunit or module of a program to be executed in a restricted environment that can prevent unanticipated or undesirable actions by that module. Extended-type objects provide a vehicle for data abstraction by allowing objects of new types to be manipulated in terms of operations that are natural for these objects. This provides a way to extend system protection features so that protection can be enforced in terms of applications-oriented operations on objects. This survey also explains one approach toward implementing these concepts thoroughly
Philip A. Myers, Subversion: The Neglected Aspect of Computer Security, Master Thesis, Naval Postgraduate School, Monterey CA 93940 (June 1980).
subversion, protection policy, trap door, Trojan horse, penetration, access control, evaluation criteria, protection system, leakage of data, security kernel
This thesis distinguishes three methods of attacking internal protection mechanisms of computers: inadvertent disclosure, penetration, and subversion. Subversion is shown to be the most attractive to the serious attacker. Subversion is characterized by three phases of operations: the inserting of trap doors and Trojan horses, the exercising of them, and the retrieval of the resultant unauthorized information. Insertion occurs over the entire life cycle of the system from the system design phase to the production phase. This thesis clarifies the high risk of using computer systems, particularly so-called 'trusted' subsystems for the protection of sensitive information. This leads to a basis for countermeasures based on the lifetime protection of security related system components combined with the application of adequate technology as exemplified in the security kernel concept.
Grace H. Nibaldi, Proposed Technical Evaluation Criteria for Trusted Computer Systems, M79-225, The MITRE Corporation, Bedford, MA 01730 (Oct. 1979).
formal verification, classification, secure computer system, trusted computing base, evaluation criteria, evaluation process, policy, mechanism, assurance, level
The DoD has established a Computer Security Initiative to foster the wide-spread availability of trusted computer systems. An essential element of the Initiative is the identification of criteria and guidelines for evaluating the internal protection mechanisms of computer systems. This report documents a proposed set of technical evaluation criteria. These criteria and any evaluation process that they might imply represent one approach to how trusted systems might be evaluated.
J. M. Schacht, Jobstream Separator System Design, MTR-3022 Vol. 1, The MITRE Corporation, Bedford, MA 01730 (May 1975).
Job stream separator, jobstream, isolation, security level, add on, reference monitor
The Jobstream Separator (JSS) has been proposed to automate the costly, inefficient, and inconvenient manual process utilized to "change colors" (security levels) at AF WWMCCS sites. The JSS would provide complete isolation among WWMCCS users and data at differing levels by introducing a secure, centralized, certifiably correct, minicomputer system to control electronic switching of peripheral devices during the system reconfiguration phase of the color change. The system would eliminate extensive operator intervention, reduce the delays incurred in the physical removal of storage media and enable the operator to change security states while maintaining overall security. This report presents a technical and economic assessment of the JSS and recommends development of a prototype system.
Roger R. Schell, Peter J. Downey, and Gerald J. Popek, Preliminary Notes on the Design of Secure Military Computer Systems, MCI-73-1, The MITRE Corporation, Bedford, MA 01730 (Jan. 1973).
secure computer system, secure model, secure design
The military has a heavy responsibility for protection of information in its shared computer systems. The military must insure the security of its computer systems before they are put into operational use. That is, the security must be "certified", since once military information is lost it is irretrievable and there are no legal remedies for redress.
Most contemporary shared computer systems are not secure because security was not a mandatory requirement of the initial hardware and software design. The military has reasonably effective physical, communication, and personnel security, so that the nub of our computer security problem is the information access controls in the operating system and supporting hardware. We primarily need an effective means for enforcing very simple protection relationships, (e.g., user clearance level must be greater than or equal to the classification level of accessed information); however, we do not require solutions to some of the more complex protection problems such as mutually suspicious processes.
Based on the work of people like Butler Lampson we have espoused three design principles as a basis for adequate security controls:
These three principles are central to the understanding of the deficiencies of present systems and provide a basis for critical examination of protection mechanisms and a method for insuring a system is secure. It is our firm belief that by applying these principles we can have secure shared systems in the next few years.
W. L. Schiller, The Design and Specification of a Security Kernel for the PDP-11/45, MTR-2934, The MITRE Corporation, Bedford, MA 01730 (Mar. 1975).
security kernel, secure computer system, specification, model
This paper presents the design of a kernel for certifiably secure computer systems being built on the Digital Equipment Corporation PDP-11/45. The design applies a general purpose mathematical model of secure computer systems to an off-the-shelf computer. An overview of the model is given. The paper includes a specification of the design that will be the basis for a rigorous proof of the correspondence between the model and the design. This design and implementation has demonstrated the technical feasibility of the security kernel approach for designing secure computer systems.
The security kernel design given in this paper is a major revision of a kernel design described in [Schiller]. In the original design a distinction was made between the information and control structures of a computer system, and the access controls dictated by our mathematical model of secure computer systems were only applied to the information structure. To protect the control structure we stated that "it is the responsibility of the system designer to systematically determine all possible channels through the control structure . . . (and prevent) the associated state variable from being controlled and/or observed". After that design was published it became obvious that the approach to protecting the control structure was not adequate. The systematic determination of channels was equivalent to having a model that protected the control structure.
Consequently, refinements were added to the model to allow the same mechanisms to protect both the information and control structure objects of a system. The basic technique used is to organize all of the data objects in the system into a tree-like hierarchy, and to assign each data and control object explicit security attributes. The major difference between the revised design given in this paper and the original design is the incorporation of the model refinements. In addition, this paper benefits from an additional years study and understanding of the computer security problem. Familiarity with the original design is not required.
Willis H. Ware, Security Controls for Computer Systems (U): Report of Defense Science Board Task Force on Computer Security, The RAND Corporation, Santa Monica, CA (Feb. 1970).
secure computing, trap door, Trojan horse, penetration, disclosure, physical security
With the advent of resource-sharing computer systems that distribute the capabilities and components of the machine configuration among several users or several tasks, a new dimension has been added to the problem of safeguarding computer-resident classified information. The basic problems associated with machine processing of classified information are not new. They have been encountered in the batch-processing mode of operation and, more recently, in the use of remote job-entry systems; the methods used to safeguard information in these systems have, for the most part, been extensions of the traditional manual means of handling classified documents.
The increasingly widespread use of resource-sharing systems has introduced new complexities to the problem. Moreover, the use of such systems has focused attention on the broader issue of using computers, regardless of the configuration, to store and process classified information.
Resource-sharing systems are those that distribute the resources of a computer system (e.g., memory space, arithmetic units, peripheral equipment, channels) among a number of simultaneous users. The term includes systems commonly called time-sharing, multiprogrammed, remote batch, on-line, multi-access, and, where two or more processors share all of the primary memory, multiprocessing. The principle distinction among the systems is whether a user must be present (at a terminal, for example) to interact with his job (time-sharing, on-line, multi-access), or whether the jobs execute autonomously (multiprogrammed, remote batch). Resource-sharing allows many people to use the same complex of computer equipment concurrently. The users are generally, although not necessarily, geographically separated from the central processing equipment and interact with the machine via remote terminals or consoles. Each users program is executed in some order and for some period of time, not necessarily to completion. The central processing equipment devotes its resources to servicing users in turn, resuming with each where it left off in the previous processing cycle. Due to the speeds of modern computers, the individual user is rarely aware that he is receiving only a fraction of the systems attention or that his job is being fragmented into pieces for processing.
Multiprogramming is a technique by which resource-sharing is accomplished. Several jobs are simultaneously resident in the system, each being handled by the various system components so as to maximize efficient utilization of the entire configuration. The operating system switches control from one job to another in such a way that advantage is taken of the machines most
Jerold Whitmore, Andre Bensoussan, Paul Green, Douglas Hunt, Andrew Kobziar, and Jerry Stern, Design for MULTICS Security Enhancements, ESD-TR-74-176, Electronic Systems Division, Air Force Systems Command, Hanscom Field, Bedford, MA 01731 (Dec. 1973).
MULTICS, containment, access control, operating system secure computing
The results of a 1973 security study of the Multics Computer System are presented detailing requirements for a new access control mechanism that would allow two levels of classified data to be used simultaneously on a single Multics system. The access control policy was derived from the Department of Defense Information Security Program. The design decisions presented were the basis for subsequent security enhancements to the Multics system.
This report documents the results of a 1973 study to identify a set of security enhancements for Honeywells Multics operating system. These enhancements were derived from the Department of Defense Information Security Program. The purpose of these enhancements was to permit users of two different security levels to simultaneously access classified information stored on the Multics system at the Air Force Data Services Center (AFDSC). This report served as a design document for the subsequent implementation of the security enhancements for use at the AFOSC.
The implementation of the design was based upon the "non-malicious" user concept. This concept is predicated upon the assumption that none of the user population would attempt malicious, concerted efforts to circumvent the enhanced security controls. The issues of guaranteeing the impenetrability of the security enhancements were not completely addressed, and the report makes no claim to the systems impenetrability. However, the proposed security controls are thought to be representative of those controls which could be provided on a certifiably secure system. The issues involved in the development of a certifiably secure system are the subject of a separate effort sponsored by the Information Systems Technology Applications Office of the Air Forces Electronic Systems Division.
During the course of the implementation of the security enhancements proposed in this report, several minor design changes were made. This report has not been updated to reflect these changes. This report should be taken neither as a precise description of the enhanced Multics system implemented for AFOSC nor as a description of Honeywells Multics Product--current or future.
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Computer Security Paper Archive Project