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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='font-size:9.5pt;font-family:"Arial","sans-serif";color:#222222;background:white'>Please note:</span><span style='font-size:9.5pt;font-family:"Arial","sans-serif";color:#222222'><br><br></span><a href="http://datatracker.ietf.org/doc/draft-hallambaker-compressedcrlset/" target="_blank"><span style='font-size:9.5pt;font-family:"Arial","sans-serif";color:#1155CC;background:white'>http://datatracker.ietf.org/doc/draft-hallambaker-compressedcrlset/</span></a><span style='font-size:9.5pt;font-family:"Arial","sans-serif";color:#222222'><br><span style='background:white'>Also note the pending IPR disclosure.</span><br><br><span style='background:white'>In brief Rob Stradling and myself have come up with a radically new</span><br><span style='background:white'>approach to certificate status that is vastly more efficient than any</span><br><span style='background:white'>previous proposal that provides finer grain certificate status than</span><br><span style='background:white'>the certificate validity interval.</span><br><br><span style='background:white'>While compressing hash tables might appear to be a fools errand, it</span><br><span style='background:white'>turns out that if the problem is correctly understood, CRLs actually</span><br><span style='background:white'>compress astonishingly well. It is actually possible to represent the</span><br><span style='background:white'>status of every one of the half million revoked certificates in the</span><br><span style='background:white'>WebPKI using fewer bytes than the heavily edited Google CRLSet.</span><br><br><span style='background:white'>There is still a powerful case for short lived certificates. But the</span><br><span style='background:white'>minimum feasible expiry interval for short lived certs is 48 hours.</span><br><span style='background:white'>Using a compressed CRL in combination with short lived certs would</span><br><span style='background:white'>allow the vulnerability window to be reduced to minutes.</span><br><br><br><span style='background:white'>We are of course aware that deployment will require a licensing regime</span><br><span style='background:white'>that meets the need of all parties including competing CAs, open</span><br><span style='background:white'>source software providers, etc. However lacking an existing licensing</span><br><span style='background:white'>regime for the rights holder (if indeed any are granted), I thought it</span><br><span style='background:white'>best to bring this to people's attention first.</span><br><br><span style='background:white'>The nature of the invention is such that not applying for a patent</span><br><span style='background:white'>would open the possibility that someone else might make a claim as has</span><br><span style='background:white'>happened to me on numerous other occasions. In the past five years</span><br><span style='background:white'>over $50 million has been spent on defending against such patent</span><br><span style='background:white'>claims.</span></span><o:p></o:p></p></div></body></html>