[BitTorrent] Back to Merkle Hash Trees...

Elliott Mitchell ehem at m5p.com
Sun Feb 6 19:01:23 EST 2005


>From: Olaf van der Spek <OvdSpek at LIACS.NL>
> Elliott Mitchell wrote:
> >>From: Olaf van der Spek <OvdSpek at LIACS.NL>
> >>Elliott Mitchell wrote:

> > one hash at a time you've generated thousands of extra protocol messages.
> > Given this you're likely to transfer blocks of hashes, at which point
> > blocks of hashes will likely be of similar size to payload blocks.
> 
> But with a different block/field/message type.

My ideas have been otherwise, simply handling blocks of hashes as any
other block of data. Pointing to payload versus internal nodes implicitly
via their indicies, but otherwise identical to any other data. My
thoughts have also not been constrained by thinking of "THEX", so I may
of been exploring cases that didn't occur in your scenarios.

Having said that I think my ideas have solidified sufficiently that I may
write them up in both code and spec form soon. At which point it will be
time to see whose ideas get shot down.

> >>It should be clear from the protocol.
> > 
> > 
> > Which is another reason I dislike THEX. The type is a protocol issue, not
> > a standards issue. You might settle on markers similar THEX, at which
> > point you've got to try both markers to distinguish the types.
> 
> Why can't you add both the markers and something else?

Inefficiency. If one fails is there any reason to believe the other will
survive? In Cryptography adding a constant payload is a big no-no, as it
aids cryptanalysis. As lower levels (TCP) will take care of errors, why
add redundancy at the application layer?

> >>If not, an internal node is 21 or 41 bytes (IIRC), so your 16 kbyte 
> >>block would not be an internal node.
> > 
> > 
> > And a payload block can't be of this size? (notably the EOF)
> > 
> > You're still assuming transfer of one hash at a time, which is worthless
> 
> Am I?

Time for those write-ups.


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