Re: [Gzz] hemppah's research problems document

[hemppah]

Quoting address@hidden:

> > > To solve that problem, we need to do tree hashing (meaning that we need
> > a
> > > new kind of block id).
> > > 
> > > -b. 
> > > 
> > 
> > So, this *might* be an issue ?
> 
> Hm, you can look at it like this: It is an issue, but probably the solution
> is really straight-forward. I suggest a structure similar to bitzi's
> urn:bitprint: 
> (IIRC).
> 
> > I went and searched some basic information about Tiger Tree Hashing
> (which
> > is
> > tree based hashing algrorithm). I found this from slashdot.org:
> [snip]
> 
> I suggest you first read about Merkle hash trees-- a good crypto book
> should
> have that, I think; then about THEX, which is a specification for 
> creating Merkle hash trees (pretty straight-forward); and then about Tiger,
> which is a message digest algorithm like SHA-1. Tigertree hashing then is 
> simply THEX using the Tiger message digest.
> 
> The important theoretical part is Merkle hash trees; Tigertree is simply
> that with a few options selected (digest=Tiger, block size=1KB and so on). 
> That's important for practice so that different implementations will be
> able
> to interoperate (if they used different digest algorithms or block sizes,
> they 
> wouldn't be).
> 
> Of course, if you know all about tree hashing already, there isn't much
> left
> to do.
> 

There's a one obvious benefit when downloading data blocks from several hosts:
hotspots, typical for DHTs, are reduced, since other nodes don't strain only one
node with their requests. Instead, fragments of data block are downloaded
simultaneously from several hosts, which have the specific data block/fragment
of data block.

Again, just for an example, in Overnet, one can start downloading a fragment of
data block from another source as soon as the other source has downloaded this
specific fragment. This ensures fast and natural distribution of content, and at
the same time, system avoids possible hotspots.


-Hermanni



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