Efficient dynamic-resharing “verifiable secret sharing” against mobile adversary

Noga Alon, Zvi Galil, Moti Yung

Research output: Chapter in Book/Report/Conference proceedingConference contribution

18 Scopus citations


We present the notion of "Dynamic Re-sharing Verifiable Secret Sharing" (VSS) where the dealing of shares is dynamically and randomly refreshed (without changing or corrupting the secret). It works against the threat of the recently considered mobile adversary that may control all the trustees, but only a bounded number thereof at any time period. VSS enables a dealer to distribute its secret to a set of trustees, so that they are assured that the sharing is vMid and that they can open it later, and further no small group of trustees can open it prematurely. Recently, such sharing of cryptographic tools gained much attention, e.g., in the context of "key escrow cryptography;' where a user enables a group of trustees to potentially open its information (when authorized by the Court). Our dynamic-sharing VSS allows for mobile adversary attacking different sets of trustees at different time periods (modeling, e.g., network viruses that get spread as well as get elinlinated). Technically, we concentrate on simple direct methods that are conlbinatorim and number-theoretic in nature, and employ only simple public-key functions. (All previous schemes withstanding linear number of faults embedded secrets in polynomials which we do not do). In addition, our protocols are constant round. The work is a sequence of reductions. We reduce t(t < n(1/2-ε)) out-of n VSS from n out-of n one (assuming ex-or honmmorphic encryption), then we reduce dynamic resharing (by th e dealer) VSS from the static VSS, finally we reduce proactive VSS (dynamic VSS with no dealer presence after the initial sharing) from our dynamic resharing VSS.

Original languageEnglish (US)
Title of host publicationAlgorithms - ESA 1995 - 3rd Annual European Symposium, Proceedings
EditorsPaul Spirakis
PublisherSpringer Verlag
Number of pages15
ISBN (Print)3540603131, 9783540603139
StatePublished - 1995
Externally publishedYes
Event3rd Annual European Symposium on Algorithms, ESA 1995 - Corfu, Greece
Duration: Sep 25 1995Sep 27 1995

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Other3rd Annual European Symposium on Algorithms, ESA 1995

All Science Journal Classification (ASJC) codes

  • Theoretical Computer Science
  • General Computer Science


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