Schloss Dagstuhl - Leibniz-Zentrum für Informatik GmbH Schloss Dagstuhl - Leibniz-Zentrum für Informatik GmbH scholarly article en Canetti, Ran; Cheung, Ling; Kaynar, Dilsun; Lynch, Nancy; Pereira, Olivier License: Creative Commons Attribution 4.0 license (CC BY 4.0)
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URN: urn:nbn:de:0030-drops-18908

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Modeling Computational Security in Long-Lived Systems



For many cryptographic protocols, security relies on the assumption
that adversarial entities have limited computational power.
This type of security degrades progressively over the lifetime of a protocol.
However, some cryptographic services, such as timestamping services or
digital archives, are emph{long-lived} in nature; they are expected to be
secure and operational for a very long time (ie super-polynomial).
In such cases, security cannot be guaranteed in the traditional sense:
a computationally secure protocol may become insecure if the attacker
has a super-polynomial number of interactions with the protocol.

This paper proposes a new paradigm for the analysis of long-lived
security protocols.
We allow entities to be active for a potentially unbounded amount of
real time, provided they perform only a polynomial amount of work emph{per
unit of real time}.
Moreover, the space used by these entities is allocated dynamically and must be
polynomially bounded.
We propose a new notion of emph{long-term implementation}, which is an
adaptation of computational indistinguishability to the long-lived
We show that long-term implementation is preserved under polynomial parallel
composition and exponential sequential composition.
We illustrate the use of this new paradigm by analyzing some security
properties of the long-lived timestamping protocol of Haber and Kamat.

BibTeX - Entry

  author =	{Canetti, Ran and Cheung, Ling and Kaynar, Dilsun and Lynch, Nancy and Pereira, Olivier},
  title =	{{Modeling Computational Security in Long-Lived Systems}},
  booktitle =	{Theoretical Foundations of Practical Information Security},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2009},
  volume =	{8491},
  editor =	{Ran Canetti and Shafi Goldwasser and G\"{u}nter M\"{u}ller and Rainer Steinwandt},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{},
  URN =		{urn:nbn:de:0030-drops-18908},
  doi =		{10.4230/DagSemProc.08491.3},
  annote =	{Keywords: Long lived security; universally composable security;}

Keywords: Long lived security; universally composable security;
Seminar: 08491 - Theoretical Foundations of Practical Information Security
Issue date: 2009
Date of publication: 27.02.2009

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