Hello:
This is Jim Hughes, General Chair of CRYPTO2002. There are three
significant Rump session papers on hash collisions that will be
presented, including an update on this one (and about 40 other short
papers on other aspects of cryptography). As the session firms up, more
information it will be posted at
http://www.iacr.org/conferences/crypto2004/rump.html
Barring technical or other difficulties, if you want to hear this from
the horses mouth, the CRYPTO2004 Rump Session will be webcast at 7pm
pacific Tuesday Aug 17 for as long as it takes. You may join us
virtually using the following links (depending on the readers).
Internet Explorer
http://128.111.55.99/crypto.htm
Microsoft media server
mms://128.111.55.99/crypt
The players (for MS and Mac) are available from
http://www.microsoft.com/windows/windowsmedia/players.aspx
I assume MS clients will be able to cope. I know that my MacOSX machine
with Windows Media Player can use the mms: link. I welcome feedback
from anyone using other readers on other platforms like Linux.
The server is currently up and running and is broadcasting a dark,
empty, and silent hall. This should be more interesting after sunup
Tuesday Santa Barbara time. You may expect sound near to the start
time.
This is our the conferences first webcast, and I hope that it works for
you. If there are problems, I will apologize in advance.
Thanks
jim
On Aug 16, 2004, at 9:02 PM, Eric Rescorla wrote:
I've now successfully reproduced the MD5 collision result. Basically
there are some endianness problems.
The first problem is the input vectors. They're given as hex words, but
MD5 is defined in terms of bitstrings. Because MD5 is little-endian,
you
need to reverse the written byte order to generate the input data. A
related problem is that some of the words are given as only 7 hex
digits. Assuming that they have a leading zero fixes that
problem. Unfortunately, this still doesn't give you the right hash
value.
The second problem, which was found by Steve Burnett from Voltage
Security, is that they authors aren't really computing MD5. The
algorithm is initialized with a certain internal state, called an
Initialization Vector (IV). This vector is given in the MD5 RFC as:
word A: 01 23 45 67
word B: 89 ab cd ef
word C: fe dc ba 98
word D: 76 54 32 10
but this is little-endian format. So, the actual initialization values
should be 0x67452301, etc...
The authors use the values directly, so they use: 0x01234567,
etc... Obviously, this gives you the wrong hash value. If you use these
wrong IVs, you get a collision... though strangely with a different
hash
value than the authors provide. Steve and I have independently gotten
the same result, though of course we could have made mistakes...
So, this looks like it isn't actually a collision in MD5, but rather in
some other algorithm, MD5'. However, there's nothing special about the
MD5 IV, so I'd be surprised if the result couldn't be extended to real
MD5.
-Ekr
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