<html> <head> <style> .hmmessage P { margin:0px; padding:0px } body.hmmessage { FONT-SIZE: 10pt; FONT-FAMILY:Tahoma } </style> </head> <body class='hmmessage'>You are right when we use a SHA1 hash, I'm not sure what I was thinking there.<BR>  <BR> I hope client developers start implementing this XEP. I only know two implementations so far. If it was widespread we could implement something like <A href="http://brightkite.com/">http://brightkite.com/</A> using XMPP!<BR><BR><BR><BR><BR> <HR id=EC_stopSpelling> <BR> Date: Fri, 31 Oct 2008 10:50:20 +0200<BR>From: norman@rasmussen.co.za<BR>To: jdev@jabber.org<BR>Subject: Re: [jdev] GEOLOC Support<BR><BR><BR> <DIV class=EC_gmail_quote> <BLOCKQUOTE class=EC_gmail_quote style="PADDING-LEFT: 1ex; BORDER-LEFT: #ccc 1px solid"> <DIV> <DIV class=EC_Ih2E3d>I misunderstood the purpose of the hash. I thought the client was expected to unhash it and use it to determine the capabilities. I didnt realize it was used to compare caps efficiently.<BR></DIV></DIV></BLOCKQUOTE></DIV> <DIV><BR></DIV>Hashes are one-way, so it's very hard (i.e. you often need to brute force), to reverse the calculation.  Hashes are a quick and easy way though to compute a 'fingerprint' for a set of data, so that you can easily determine if you've seen it before (by comparing the hashes), or not (and then you can do the 'expensive' disco query to get the data that the hash was computed from).  Clients need to store the disco result along with it's hash, so that when they see the same hash again, they know what the result was, and they don't need to re-query it.<BR clear=all><BR>-- <BR>- Norman Rasmussen<BR>- Email: <A href="mailto:norman@rasmussen.co.za">norman@rasmussen.co.za</A><BR>- Home page: <A href="http://norman.rasmussen.co.za/" target=_blank>http://norman.rasmussen.co.za/</A> <br /><hr />Store, manage and share up to 5GB with Windows Live SkyDrive. <a href='http://skydrive.live.com/welcome.aspx?provision=1?ocid=TXT_TAGLM_WL_skydrive_102008' target='_new'>Start uploading now</a></body> </html>