Re: [9fans] In case anyone worries about block hash collision in venti

[erik quanstrom <quanstro@quanstro.net>]

> > If you are really paranoid and don't want any collisions in the next
> > 10 years: don't let strangers in your venti.
>
> Which, to close the circle, as Tim points out, you are always doing,
> each time you receive an email :-)

not all email is from strangers.

in mbox format, messages are concatinated.  for a block
size of b, the size of the existing mailbox is 0 ... b-1 mod b.
therefore, there is a 1/b chance of the attack succeeding, even
if the attacker knows the block size and pads to the next
block.  i suppose that this is a fair assumption, since we're
given that the attacker is attacking venti.

this is esentially the same reason that mbox format will eat alot
of storage, even if you're using venti.

- erik