Re: [Gzz] hemppah's research problems document

[hemppah]

Quoting address@hidden:

> > The problem is finding the hashes of the miniblocks from the block id: if
> > someone
> > gets to do this in a hostile way you could download a lot of miniblocks
> to
> > discover
> > in the end that you got a lot of garbage, because one of the miniblocks
> is
> > wrong.
> > 
> > But aside from that, this should be no problem.
> 
> 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 ?

I went and searched some basic information about Tiger Tree Hashing (which is
tree based hashing algrorithm). I found this from slashdot.org:

- - -
...

TTH (Tiger Tree Hashing) is used to validate/verify chunks or segements of files
as they download. SHA1 is still used in Shareaza, and is still a standard on
Gnutella (has the lowest collision rate compared to MD4, MD5).

For example, say your downloading an 800MB Linux Distro. Some script kiddie
fakes their Porn video as a Linux distro (really hard to do, but for the sake of
discussion..). Shareaza will download a segement from that node, but it will use
Tiger Tree Hashing to check if that chunk of the file is correct or not. Of
course, it won't be. So it will delete it and ban that node from the download
transfer circle and re-download that chunk again from a different node. Without
TTH, it would of only caught the invalidation after the file had completed
(after you downloaded that whole damn 800MB file, and it's corrupt?!)

So basicaly, TTH verify's segments of files (great for swarming (downloading
from multiple sources)). So, theoretically, you will never get an invalid file
when downloading on Shareaza from other Shareaza nodes (Shareaza currently is
the only client that supports TTH).

- - -

-Hermanni

-------------------------------------------------
This mail sent through IMP: http://horde.org/imp/