The Dyad project at Carnegie Mellon University is using physically secure coprocessors to achieve new protocols and systems addressing a number of perplexing security problems. These coprocessors can be produced as boards or integrated circuit chips and can be directly inserted in standard workstations or PC-style computers. This paper presents a set of security problems and easily implementable solutions that exploit the power of physically secure coprocessors: (1) protecting the integrity of publicly accessible workstations, (2) tamper-proof accounting/audit trails, (3) copy protection, and (4) electronic currency without centralized servers. We outline the architectural requirements for the use of secure coprocessors. 1 Introduction and Motivation The Dyad project at Carnegie Mellon University is using physically secure coprocessors to achieve new protocols and systems addressing a number of perplexing security problems. These coprocessors can be produced as boards or integrated ...

Many distributed systems manage some form of long-lived data, such as files or data bases. The performance and fault-tolerance of such systems may be enhanced if the repositories for the data are physically distributed. Nevertheless, distribution makes security more difficult, since it may be difficult to ensure that each repository is physically secure, particularly if the number of repositories is large. This paper proposes new techniques for ensuring the security of long-lived, physically distributed data. These techniques adapt replication protocols for fault-tolerance to the more demanding requirements of security. For a given threshold value, one set of protocols ensures that an adversary cannot ascertain the state of a data object by observing the contents of fewer than a threshold of repositories. These protocols are cheap; the message traffic needed to tolerate a given number of compromised repositories is only slightly more than the message traffic needed to tolerate the same number of failures. A second set of protocols ensures that an object’s state cannot be altered by an adversary who can modify the contents of fewer than a threshold of repositories. These protocols are more expensive; to tolerate t-1 compromised repositories, clients executing certain operations must communicate with t-1 additional sites.

: This report summarizes the analysis of survivability-related requirements and their interdependence. It also identifies inadequacies in existing commercial systems and the absence of components that hinder the attainment of survivability. It recommends specific architectural structures and other approaches that can help overcome those inadequacies. The field of endeavor addressed in this report is inherently open ended. New research results and new software components are emerging at a rapid pace. For this reason, the report stresses fundamentals, and is intended to be a guide to certain principles and architectural directions whose systematic use can lead to better survivability. In that spirit, the report is intended to serve as a coherent resource from which many further resources can be gleaned by following the cited references and URLs. The report is quite modest in its intent. It does not try to solve all the problems of how to develop, maintain, and use highly survivable syste...

Abstract. Redundancy and diversity are commonly applied principles for fault tolerance against accidental faults. Their use in security, which is attracting increasing interest, is less general and less of an accepted principle. In particular, redundancy without diversity is often argued to be useless against systematic attack, and diversity to be of dubious value. This paper discusses their roles and limits, and to what extent lessons from research on their use for reliability can be applied to security, in areas such as intrusion detection. We take a probabilistic approach to the problem, and argue its validity for security. We then discuss the various roles of redundancy and diversity for security, and show that some basic insights from probabilistic modelling in reliability and safety indeed apply to examples of design for security. We discuss the factors affecting the efficacy of redundancy and diversity, the role of “independence ” between layers of defense, and some of the trade-offs facing designers. 1.

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Introduction Security is a pressing problem for distributed systems. Distributed systems exchange data among a variety of users over a variety of sites, which may be geographically separated. A user who stores important data on processor A must trust not just processor A but also the processors B; C;D; . . . with which A communicates. The distributed security problem is difficult, and few major distributed systems attempt to address it. In fact, conventional approaches to computer security are so complex that they actually discourage designers from trying to build a secure distributed system: A software engineer who wishes to build a secure distributed data application finds that he or she must depend on the security of a distributed database which depends on the security of a distributed file system which depends on the security of a distributed operating system kernel, etc. Under

As Century 21 just opened up, it is a fitting time to reflect on the evolution of the fault-tolerant distributed computing technology that occurred in the last century. The author's view of that evolution is sketched in this paper with emphasis on the major issues insufficiently resolved in Century 20. Such issues are naturally among what this author believes to be the prime subjects that need to be addressed in this decade by the research community. A substantial part of this paper deals with the issues that need to be resolved to advance the real-time fault-tolerant distributed computing branch into a mature practicing field.