<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div><div><br></div>On 19 Aug 2016, at 05:54, Jerry Leichter <<a href="mailto:leichter@lrw.com">leichter@lrw.com</a>> wrote:<br><br></div><blockquote type="cite"><meta http-equiv="Content-Type" content="text/html charset=us-ascii"><div><blockquote type="cite" class=""><div class=""><div bgcolor="#FFFFFF" text="#000000" class=""><blockquote class="">Coins could be made out of glass. Flaws like tiny
bubbles would be difficult to position during manufacture. As such
imperfections would make each coin unique and impossible to
replicate. Whatever process is used to draw a picture and a coin
value could be used to add a unique serial number. Authentication
would involve authenticating the physical properties like
refractive index and examining the coin's unique physical flaws
i.e. Fingerprint. Finally the central bank, for that currency, can
authenticate that 'serial number - fingerprint' combination.<br class="">
</blockquote>
</div></div></blockquote></div>There is a great deal of published work in this direction. One extreme example (first page only; the paper should be around somewhere) <a href="http://link.springer.com/chapter/10.1007%2F978-3-642-04431-1_15#page-1" class="">http://link.springer.com/chapter/10.1007%2F978-3-642-04431-1_15#page-1</a>. (A "PUF" is a Physically Uncloneable Function" - this search term will lead you to some of the published work. The particular paper - which I haven't read - uses a "PPUF" - a Public PUF).<div class="">.....</div><div class="">An actual fielded system - to which I don't have a reference; this is from memory - was used to make tamperproof seals: It's possible to pull a length of many fiber-optic strands. The individual strands assort and mix themselves quite randomly, unpredictably, and uncontrollably. Pick some number of them at one end and light them; record which ones are lit at the other. Thread the glass through a hasp controlling access to something. If it's cut, there's no known way to repair or replace it such that the resulting strand will reproduce the pattern.</div><div class=""><br></div></blockquote><blockquote type="cite"><div class=""><div class=""> </div></div></blockquote><div>Similar examples abound in nuclear n<span style="background-color: rgba(255, 255, 255, 0);">onproliferation research (and day to day practice!). </span></div><div><span style="background-color: rgba(255, 255, 255, 0);"><br></span></div><div><span style="background-color: rgba(255, 255, 255, 0);">Examples are intentionally scratching (with a steel wire brush) or splattering (with solder or metal welding blobs) the bolts closing a container and comparing photographs. </span></div><div><br></div><div>The search term "safeguards" together with tamper proof and variations thereof, or the annual research progress reports of the secretariats of the international treaties(below), may be helpful when researching this generally very mature and robust field. </div><div><br></div><div>A field that may be of interest to this community - as it has state level actors and nations at the core of its threat model. </div><div><br></div><div>Rather than consider these rather late in the game - as is common in the IT space. </div><div><br></div><div>And due to the diplomatic nature of robust international treaties - reports back rather transparent on what (sophisticated) state actors are doing to keep each other collectively in check, what works and what failed. </div><div><br></div><div><span style="background-color: rgba(255, 255, 255, 0);">As a result -most papers are very engineering oriented and more reports from the field than theoretical. </span></div><div><br></div><div>Dw. </div><div><br></div><div><a href="https://www.iaea.org/safeguards/">https://www.iaea.org/safeguards/</a></div><div><a href="http://www.un.org/en/conf/npt/2015/index.shtml">http://www.un.org/en/conf/npt/2015/index.shtml</a></div><div><span style="background-color: rgba(255, 255, 255, 0);"><br></span></div><div><br></div><div><br></div><br><blockquote type="cite"><div><div class=""><div class=""> -- Jerry</div></div><div class=""><br class=""></div></div></blockquote><blockquote type="cite"><div><span>_______________________________________________</span><br><span>The cryptography mailing list</span><br><span><a href="mailto:cryptography@metzdowd.com">cryptography@metzdowd.com</a></span><br><span><a href="http://www.metzdowd.com/mailman/listinfo/cryptography">http://www.metzdowd.com/mailman/listinfo/cryptography</a></span></div></blockquote></body></html>