Re: K-of-N information dispersal for Mixmaster

[George Danezis <gd@theory.lcs.mit.edu>]

The issue of how large messages are to be split, and how to make copies of 
messages for reliability reasons, is worth standardizing. Of course it is 
not a matter of concern for the mix nodes and therefore including it in 
the minion-spec would not be appropriate. 

Instead I have left a big blank section in the nym-server definition, 
where we can define a reliable, authenticated (with anonymous signatures), 
transport layer (a bit like TCP on top of IP). Of course one has to be 
careful not to jeopardize anonymity while constructing it.

Yours,

George

On Tue, 20 Aug 2002, David Hopwood wrote:

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> Nomen Nescio wrote (on alt.privacy.anon-server and sci.crypt):
> > 
> > Problem.  In the mixnet remailer system, large messages
> > are split up into a sequence of short fixed-size chunks,
> > mailed through different chains, and reassembled at the
> > exit point.  If one or more of the pieces fails to arrive,
> > reassembly fails and the entire message is lost.
> > 
> > Wouldn't this be a good case for using an Information
> > Dispersal Algorithm which is redundant enough to allow full
> > recovery of the original data even in a lossy environment?
> > 
> > This would make the remailer system fairly tolerant of high
> > rates of dropout, single-packet delays, local gridlock, etc,
> > with only 10%-20% overhead even for very large split messages.
> > 
> > Would this be an issue to raise with Lance Cottrell, or has
> > he passed the mantle to another vic^H^H^H maintainer?
> 
> I suggest discussing it on the mixminion-dev mailing list, which is
> designing the Type III remailer protocol (archive and subscription info
> at <http://archives.seul.org/mixminion/dev/>).
> See <http://www.mixminion.net/> for a draft paper on the design.
> 
> My immediate take on this is that it's an end-to-end issue, and does not
> require support in intermediate nodes. But yes, it would probably be a
> good idea to support an IDA when fragmenting/reassembling messages.
> 
> - -- 
> David Hopwood <david.hopwood@zetnet.co.uk>
> 
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