[cryptography] rolling hashes, EDC/ECC vs MAC/MIC, etc.

travis+ml-rbcryptography at subspacefield.org travis+ml-rbcryptography at subspacefield.org
Fri May 20 17:30:21 EDT 2011


Hmm, after sending this to some of you I remembered this list :-)

====

Just a quick thought, I noticed the other day that rsync uses a
"rolling MD4 hash" or something like that to detect changes in a
window of data.

I wonder if A/V shouldn't use something similar?

I assume MD4 is an outdated choice - perhaps some cryppie needs to
design a hash function that is specifically designed for a FIFO kind
of window?  Maybe there is and I'm just out of the loop.

Potentially another application is for "metadata silvering" on file
systems like ZFS, where we want to keep an updated checksum for a
file, to detect corruption, but still want to have, say, efficient
writing to the file - can you support appending?  How about random access?

Also, FEC defends against an unintelligent adversary; I wonder if we
couldn't defend against stronger ones (MAC/MIC) efficiently and
neutralize the unintelligent one (nature and errors) for free?  It
seems a shame to tack two sets of metadata onto our data.

==== shameless plug follows ====

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http://base.bitrot.info/

Anyone can join the mlist, and please come out if you're in SF
sometime.

I have a few security presentations, some on crypto, and one free
online book:

http://www.subspacefield.org/security/

That is all.

Travis
-- 
http://www.subspacefield.org/~travis/
I don't believe in luck.  I believe in the law of large numbers.
If you are a spammer, please email john at subspacefield.org to get blacklisted.
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