Date: Mon, 22 Dec 2014 06:51:46 +0100 From: Hanno Böck <hanno@...eck.de> To: oss-security@...ts.openwall.com Subject: Re: can we talk about secure time? On Sun, 21 Dec 2014 12:31:07 +0100 Florian Weimer <fw@...eb.enyo.de> wrote: > Some folks want to run their servers within a few milliseconds of each > other, and do not care so much about security or resiliency. I perfectly understand that some people need more accuracy than tlsdate can give. However it's probably rare, right? I don't see any reason why average consumer hardware (Desktop, smartphone etc.) would have any problem with the 1-2 sec max inaccuracy of tlsdate. > Reconciling this with cryptography is certainly a challenge. On the > other hand, this does not have to be the default. I think it shouldn't be too hard to get both. You could do an asymmetric key exchange before you do any time transmission. Then the only thing you really need is a single authentication operation (HMAC or whatever). That shouldn't delay by any significant amount. > I think most desktop-based distributions could get away with something > like tlsdate. > > In contrast, servers with long-running connections and I/O polling > loops often do not react gracefully to jumps in time. (I once > disconnected a few hundreds, if not thousands of users from an IRC > server just by setting its time correctly.) Sure, you can avoid that > by using the appropriate kernel clock for timeout handling, but I have > the impression that the correct clock changes every couple of years. tlsdate has tlsdated, I hope it acts intelligent and doesn't do time jumps. Haven't tested though. -- Hanno Böck http://hboeck.de/ mail/jabber: hanno@...eck.de GPG: BBB51E42 Content of type "application/pgp-signature" skipped
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