On Fri, 14 Jul 2006, Travis H. wrote:
Absent other protections, one could simply write a new WORM media with
falsified information.
I can see two ways of dealing with this:
1) Some kind of physical authenticity, such as signing one's name on
the media as they are produced (this assumes the signer is not
corruptible), or applying a frangible difficult-to-duplicate seal of
some kind (this assumes access controls on the seals).
2) Some kind of hash chain covering the contents, combined with
publication of the hashes somewhere where they cannot be altered (e.g.
publish hash periodically in a classified ad in a newspaper).
My MS Thesis was on this topic:
http://lunkwill.org/cv/logcrypt_update.pdf
If you store a value with a TTP (say, an auditor), and follow the protocol
honestly, it's impossible to go back later and falsify records. The symmetric
version uses hash chains, and was invented several times before I came along.
-J
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