re s s steve b access digex com steve brinich writes second question why why is such a strange procedure used and not a real rng this turns those s s in a kind of bottleneck for system security the only theory that makes any sense is that s and s are either the same for all chips or vary among very few possibilities so that anyone trying to break the encryption by brute force need only plow through the possible serial numbers about one billion multiplied by the number of different s s combinations my interpretation of denning s description is that s and s are chosen randomly by agents of the key escrow companies at the start of each chip programming session i imagine that the chips are in a carrier which will allow them all to be programmed fairly quickly there would not be a need to transfer chips one at a time into a little pla programmer as some people have envisioned my guess as to why this procedure is used is that basing the keys on the s and s using a specified algorithm provides an in principle checkable way to verify that no back doors exist in the choice of the random numbers used to generate the keys since we have to trust the escrow companies anyway it does not weaken the system to have the keys be generated from random seeds entered by the escrow agents and since the algorithm for key generation is public modulo skipjack secrecy then in principle an agent could challenge the procedure ask for s and s to be exposed and run his own independent calculation of u and u to verify that that is what is actually being put onto the floppies and yes there are many ways in which failures to follow this scheme could be hard to check the laptop probably will not really be destroyed each time hidden cameras in the ceiling could see the s and s entered by the trusted escrow agents back doors in the chip could allow u to be recovered heck each chip could be recorded with the same u ignoring what was on the floppy hal finney
