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Long-term Security and Universal Composability
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This may allow adversaries to break a protocol retrospectively by breaking the underlying complexity assumptions long after the execution of the protocol. Long-term secure protocols, protocols that after the end of the execution do not reveal any information to a then possibly unlimited adversary, could meet this threat. On the other hand, in many applications, it is necessary that a protocol is secure not only when executed alone, but within arbitrary contexts. The established notion of universal composability (UC) captures this requirement. This is the first paper to study protocols which are simultaneously long-term secure and universally composable. We show that the usual set-up assumptions used for UC protocols (e.g., a common reference string) are not sufficient to achieve long-term secure and composable protocols for commitments or zero-knowledge protocols. We give practical alternatives (e.g., signature cards) to these usual setup-assumptions and show that these enable the implementation of the important primitives commitment and zero-knowledge protocols." /> <meta property="article:section" content="" /> <meta property="article:modified_time" content="2010-04-28T09:50:39+00:00" /> <meta property="article:published_time" content="2006-11-19T19:45:56+00:00" /> <meta property="article:tag" content="Universal Composability" /> <meta property="article:tag" content="long-term security" /> <meta property="article:tag" content="zero-knowledge" /> <meta property="article:tag" content="commitment schemes" /> </head> <body> <noscript> <h1 class="text-center">What a lovely hat</h1> <h4 class="text-center">Is it made out of <a href="https://iacr.org/tinfoil.html">tin foil</a>?</h4> </noscript> <div class="fixed-top" id="topNavbar"> <nav class="navbar navbar-custom navbar-expand-lg"> <div class="container px-0 justify-content-between 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<p class="fst-italic mb-3"> Joern Mueller-Quade and Dominique Unruh </p> <h5 class="mt-3">Abstract</h5> <p style="white-space: pre-wrap;">Algorithmic progress and future technological advances threaten today's cryptographic protocols. This may allow adversaries to break a protocol retrospectively by breaking the underlying complexity assumptions long after the execution of the protocol. Long-term secure protocols, protocols that after the end of the execution do not reveal any information to a then possibly unlimited adversary, could meet this threat. On the other hand, in many applications, it is necessary that a protocol is secure not only when executed alone, but within arbitrary contexts. The established notion of universal composability (UC) captures this requirement. This is the first paper to study protocols which are simultaneously long-term secure and universally composable. We show that the usual set-up assumptions used for UC protocols (e.g., a common reference string) are not sufficient to achieve long-term secure and composable protocols for commitments or zero-knowledge protocols. We give practical alternatives (e.g., signature cards) to these usual setup-assumptions and show that these enable the implementation of the important primitives commitment and zero-knowledge protocols.</p> <p><strong>Note:</strong> Original version 2006-11-19. Revised 2007-01-27: Incorporated TCC referee comments. Revised 2009-08-10: Strongly extended and (hopefully) improved version. (Thanks to Oded Goldreich for many comments.) Revised 2010-04-28: Many corrections and improvements. Also contains an additional section on generalising the notion of long-term revealing functionalities. (Thanks to the reviewers of the Journal of Cryptology for comments.)</p> </div> <div id="metadata" class="col-md-5 col-lg-4 ps-md-5 mt-4 mt-md-0"> <h5>Metadata</h5> <dl> <dt> Available format(s) </dt> <dd> <a class="btn btn-sm btn-outline-dark" href="/2006/422.pdf"> <img class="icon" src="/img/file-pdf.svg">PDF</a> </dd> <dt>Publication info</dt> <dd>Published elsewhere. To appear in the Journal of Cryptology</dd> <dt>Keywords</dt> <dd class="keywords"><a href="/search?q=Universal%20Composability" class="me-2 badge bg-secondary keyword">Universal Composability</a><a href="/search?q=long-term%20security" class="me-2 badge bg-secondary keyword">long-term security</a><a href="/search?q=zero-knowledge" class="me-2 badge bg-secondary keyword">zero-knowledge</a><a href="/search?q=commitment%20schemes" class="me-2 badge bg-secondary keyword">commitment schemes</a></dd> <dt>Contact author(s)</dt> <dd><span class="font-monospace"> unruh<span class="obfuscate"> @ </span>mmci uni-saarland de </span> </dd> <dt>History</dt> <dd>2010-04-28: last of 4 revisions</dd> <dd>2006-11-19: received</dd> <dd><a rel="nofollow" href="/archive/versions/2006/422">See all versions</a></dd> <dt>Short URL</dt> <dd><a href="https://ia.cr/2006/422">https://ia.cr/2006/422</a></dd> <dt>License</dt> <dd><a rel="license" target="_blank" href="https://creativecommons.org/licenses/by/4.0/"> <img class="licenseImg" src="/img/license/CC_BY.svg" alt="Creative Commons Attribution" title="Creative Commons Attribution"><br> <small>CC BY</small> </a> </dd> </dl> </div> </div> <p class="mt-4"><strong>BibTeX</strong> <button id="bibcopy" class="ms-2 btn btn-sm btn-outline-dark" aria-label="Copy to clipboard" onclick="copyBibtex()"> <img src="/img/copy-outline.svg" class="icon">Copy to clipboard</button></p> <pre id="bibtex"> @misc{cryptoeprint:2006/422, author = {Joern Mueller-Quade and Dominique Unruh}, title = {Long-term Security and Universal Composability}, howpublished = {Cryptology {ePrint} Archive, Paper 2006/422}, year = {2006}, url = {https://eprint.iacr.org/2006/422} } </pre> <script> var bibcopy; function triggerTooltip() { console.log('setting tooltip'); } window.onload = triggerTooltip; function copyBibtex() { let range = document.createRange(); range.selectNode(document.getElementById('bibtex')); window.getSelection().removeAllRanges(); window.getSelection().addRange(range); document.execCommand('copy'); window.getSelection().removeAllRanges(); let bibcopy = document.getElementById('bibcopy'); let copyTooltip = new bootstrap.Tooltip(bibcopy, {trigger: 'manual', title: 'Copied!'}); copyTooltip.show(); setTimeout(function() { copyTooltip.dispose(); }, 2000); } </script> </main> <div class="container-fluid mt-auto" id="eprintFooter"> <a href="https://iacr.org/"> <img id="iacrlogo" src="/img/iacrlogo_small.png" class="img-fluid d-block mx-auto" alt="IACR Logo"> </a> <div class="colorDiv"></div> <div class="alert alert-success w-75 mx-auto"> Note: In order to protect the privacy of readers, eprint.iacr.org does not use cookies or embedded third party content. </div> </div> <script src="/css/bootstrap/js/bootstrap.bundle.min.js"></script> <script> var topNavbar = document.getElementById('topNavbar'); if (topNavbar) { document.addEventListener('scroll', function(e) { if (window.scrollY > 100) { topNavbar.classList.add('scrolled'); } else { topNavbar.classList.remove('scrolled'); } }) } </script> </body> </html>