Reaching Agreement in the Presence of Faults (original) (raw)

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Published: 01 April 1980 Publication History

Abstract

The problem addressed here concerns a set of isolated processors, some unknown subset of which may be faulty, that communicate only by means of two-party messages. Each nonfaulty processor has a private value of information that must be communicated to each other nonfaulty processor. Nonfaulty processors always communicate honestly, whereas faulty processors may lie. The problem is to devise an algorithm in which processors communicate their own values and relay values received from others that allows each nonfaulty processor to infer a value for each other processor. The value inferred for a nonfaulty processor must be that processor's private value, and the value inferred for a faulty one must be consistent with the corresponding value inferred by each other nonfaulty processor.

It is shown that the problem is solvable for, and only for, n ≥ 3_m_ + 1, where m is the number of faulty processors and n is the total number. It is also shown that if faulty processors can refuse to pass on information but cannot falsely relay information, the problem is solvable for arbitrary nm ≥ 0. This weaker assumption can be approximated in practice using cryptographic methods.

References

[1]

DAvIEs, D, AND WAKEH~Y, J. Synchronization and matching m redundant systems IEEE Trans on Comptrs. C-27, 6 (June 1978), 531-539.

[2]

DIFFIE, W, AND BELLMAN, M. New dtrections in cryptography. IEEE Trans Inform. Theory IT-22, 6 (Nov 1976), 644-654

[3]

RIVEST, R.L., SHArerS, A, Am) ADLEMAN, L A A method for obtaming dtgltal signatures and pubhc-key cryptosystems. Comm. ACM 21, 2 (Feb 1978), 120-126.

[4]

WENSLEY, J H., ET ^L. SIFT: destgn and analysis of a fault-tolerant computer for aircraft control Proc. IEEE 66, 10 (Oct. 1978), 1240-1255.

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Published In

cover image Journal of the ACM

Journal of the ACM Volume 27, Issue 2

April 1980

196 pages

Copyright © 1980 ACM.

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Association for Computing Machinery

New York, NY, United States

Publication History

Published: 01 April 1980

Published in JACM Volume 27, Issue 2

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M. Pease

Computer Science Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA

R. Shostak

Computer Science Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA

L. Lamport

Computer Science Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA