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USENIX, The Advanced Computing Systems Association

2006 USENIX Annual Technical Conference Abstract

Pp. 85–90 of the Proceedings

Compare-by-Hash: A Reasoned Analysis

J. Black, University of Colorado, Boulder


Compare-by-hash is the now-common practice used by systems designers who assume that when the digest of a cryptographic hash function is equal on two distinct files, then those files are identical. This approach has been used in both real projects and in research efforts (for example rysnc [16] and LBFS [12]). A recent paper by Henson criticized this practice [8]. The present paper revisits the topic from an advocate's standpoint: we claim that compare-by-hash is completely reasonable, and we offer various arguments in support of this viewpoint in addition to addressing concerns raised by Henson.
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Last changed: 15 Sept. 2006 ch