[BitTorrent] SHA-0 Broken, MD5 Rumored Broken

Elliott Mitchell ehem at m5p.com
Thu Aug 19 17:27:44 EDT 2004

>From: xtf2007 <OvdSpek at LIACS.NL>
> http://slashdot.org/articles/04/08/17/0030243.shtml?
> tid=93&tid=162&tid=1&tid=218

Three key things, first, notice the key word, "rumor". Second, this is a
week varient of SHA-1, not SHA-1 itself. Third, so far they're only
talking about breaking the strongly collision free property, not the
weakly collision free property (and the integrity checks depend on the
latter, not the former).

Having said that, there does appear to be some truth to the rumor. There
is also the possibility that the attack could be extended to a full
break. It will also be pretty simple to move to other hashes, so even if
this does turn out to be a big deal in the crypto community, it won't be
a big deal for BitTorrent.

I'd tend towards adding a "hashtype" field in torrent files so hashes of
the same size can be distinguished; might be interesting to allow
multiple hash types in the same torrent file.

(\___(\___(\______          --=> 8-) EHM <=--          ______/)___/)___/)
 \   (    |         EHeM at gremlin.m5p.com PGP 8881EF59         |    )   /
  \_  \   |  _____  -O #include <stddisclaimer.h> O-   _____  |   /  _/
    \___\_|_/82 04 A1 3C C7 B1 37 2A*E3 6E 84 DA 97 4C 40 E6\_|_/___/

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