[mythtv-users] Mooting architecture for a DataDirect replacement

Rod Smith mythtv at rodsbooks.com
Mon Jun 25 14:48:24 UTC 2007


On Monday 25 June 2007 09:53, Jay R. Ashworth wrote:
> On Sun, Jun 24, 2007 at 01:11:17PM -0400, Rod Smith wrote:
>
> I'm of two minds about whether the location of the public key should be
> *in* the message; I suspect not, though a digest of the public key
> could be usefully included.

If either the public key or its location is in the message, then that sort of
defeats the purpose of key-signing the message -- anybody who wanted to could
create a malicious set of changes, sign them, post them, and they'd all check
out OK. For this side of things, I think you'd need a central Web site
(possibly with mirrors) to host public keys, possibly grouped into different
categories. Client software could then be configured to accept keys in
certain categories or specific sets of keys.

> > > And there's still nothing you can do about a posting that never
> > > arrives.
> >
> > *ONCE AGAIN*: There's par2, which is designed for precisely this
> > purpose.
>
> Yeah, but given the possibility of multiple valid update sources for a
> given program's data (which is a possibility I admit I probably haven't
> mentioned until now, but that I think would be useful in several
> circumstances including those noted above)... I don't think we can.
>
> Or at least, not authoritatively.

I don't think there's anything about par2 that requires the
checksum/correction posts need to come from the same source as the originals.
In principle, you could have a program watching a reliable NNTP server that
downloads the posts, creates par2 files every now and then, and posts them.
The trickiest part to planning this, as far as I can see, is in figuring out
what to include in the par2 posts. You'd have to use some sort of algorithm
that would make it easy for clients with missing data they want to recreate
to figure out which par2 posts to download, and which regular files they'd
need to retrieve.

It could be easier to just maintain a separate server (HTTP, FTP, NNTP, or
whatever) that's open to all but intended only for retrieving missing posts.

-- 
Rod Smith
http://www.rodsbooks.com


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