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more info from talk at MIT yesterday.
The folks from the NSA said the following about key generation:
- each escrow agency provides a "seed key", seed1 and seed2
- the box which programs the chip generates two random keys,
random1 and random2
- for each chip programmed during that batch (which is "12 to
14 hours of production"), the box computes a
classified deterministic function
(U1, U2) = F(serial, random1, random2, seed1, seed2)
to generate the unit keys
They did *not* explicitly say that the random seeds were destroyed at
the end of the production run.
Also, someone asked
"How do we know that the unit key isn't a hash function of
the chip serial number?"
The answer was:
"You don't".
They also confirmed Tom Knight's suspicions about what they're going
to do when someone reverse engineers the chip and publishes the
Skipjack algorithm & the family key: they've got a patent application
filed, under a secrecy order; if the algorithm is published, they'll
lift the secrecy order and have the patent issued, and use that to go
after anyone making a compatible version.
They also had a comment that they considered Blaze's findings to be
mostly irrelevant, as the only people who would use it would be
persons who *didn't* trust the escrow system, but *did* trust the
algorithm...
- Bill