Showing papers by "Michael Merritt published in 1993"

Augmented encrypted key exchange: a password-based protocol secure against dictionary attacks and password file compromise

Abstract: The encrypted key exchange (EKE) protocol is augmented so that hosts do not store cleartext passwords. Consequently, adversaries who obtain the one-way encrypted password file may (i) successfully mimic (spoof) the host to the user, and (ii) mount dictionary attacks against the encrypted passwords, but cannot mimic the user to the host. Moreover, the important security properties of EKE are preserved—an active network attacker obtains insufficient information to mount dictionary attacks. Two ways to accomplish this are shown, one using digital signatures and one that relies on a family of commutative one-way functions.

Atomic snapshots of shared memory

Abstract: This paper introduces a general formulation of atomic snapshot memory, a shared memory partitioned into words written (updated) by individual processes, or instantaneously read (scanned) in its entirety. This paper presents three wait-free implementations of atomic snapshot memory. The first implementation in this paper uses unbounded (integer) fields in these registers, and is particularly easy to understand. The second implementation uses bounded registers. Its correctness proof follows the ideas of the unbounded implementation. Both constructions implement a single-writer snapshot memory, in which each word may be updated by only one process, from single-writer, n-reader registers. The third algorithm implements a multi-writer snapshot memory from atomic n-writer, n-reader registers, again echoing key ideas from the earlier constructions. All operations require Θ(n2) reads and writes to the component shared registers in the worst case. —Authors' Abstract

Lazy caching

Abstract: This paper examines cache consistency conditions for multiprocessor shared memory systems. It states and motivates a weaker condition than is normally implemented. An algorithm is presented that exploits the weaker condition to achieve greater concurrency. The algorithm is shown to satisfy the weak consistency condition. Other properties of the algorithm and possible extensions are discussed.

Cryptographic protocol for remote authentication

Abstract: A cryptographic communication system is disclosed which permits computer users to authenticate themselves to a computer system without requiring that the computer system keep confidential the password files used to authenticate the respective user's identities. The invention is useful in that it prevents a compromised password file from being leveraged by crafty hackers to penetrate the computer system.

Atomic Transactions: In Concurrent and Distributed Systems

Abstract: From the Publisher: This book develops a theory for transactions that provides practical solutions for system developers, focusing on the interface between the user and the database that executes transactions. Atomic transactions are a useful abstraction for programming concurrent and distributed data processing systems. Presents many important algorithms which provide maximum concurrency for transaction processing without sacrificing data integrity. The authors include a well-developed data processing case study to help readers understand transaction processing algorithms more clearly. The book offers conceptual tools for the design of new algorithms, and for devising variations on the familiar algorithms presented in the discussions. Whether your background is in the development of practical systems or formal methods, this book will offer you a new way to view distributed systems.

Benign Failure Models for Shared Memory (Preliminary Version)

Abstract: This paper introduces two benign failure models for shared memory in distributed systems, crash-omission and crash-eventual. These models are of intermediate power between the crash model and omission models of [JCT92]. (They exhibit more faulty behaviors than crash and fewer than omission.) Unlike the crash model, crash-omission is shown to have universal, gracefully-degrading constructions. That is, for any integer k, any shared object may be constructed from shared registers and consensus objects, so that: (1) if no more than k of the components suffer crash-omission failures, the constructed object exhibits no failures, and (2) if more than k of the components suffer crash-omission failures, the constructed object exhibits crash-omission failures.

Knowledge in shared memory systems

Abstract: We study the relation between knowledge and space. That is, we analyze how much shared memory space is needed in order to learn certain kinds of facts. Such results are useful tools for reasoning about shared memory systems. In addition we generalize a known impossibility result, and show that results about how knowledge can be gained and lost in message passing systems also hold for shared memory systems.

A Structural Linearization Principle for Processes

Abstract: In [1], an induction principle for processes was given which allows one to apply model-checking techniques to parameterized families of processes. A limitation of the induction principle is that it does not apply to the case in which one process depends directly upon a parameterized number of processes, which number grows without bound. This would seem to preclude its application to families of N processes interconnected in a star topology. Nonetheless, we show that if the dependency can be computed incrementally, then the direct dependency upon the parameterized number of processes may be re-expressed recursively in terms of a linear cascade of processes, yielding in effect a “linearization” of the inter-process dependencies and allowing the induction principle to apply.