> I believe the military receivers use both L1 and L2, probably using L1
> for course position and L2 for fine-tuning.  The one military unit I
saw
> also had a "kill switch" -- hitting two specific but badly marked
> buttons at once would wipe the decryption key from the unit.

I had some fun with that years back, storing DES keys in SRAM.
Interesting thing, when the keys had sat in SRAM for months, it was
actually very hard to get them to erase just by pulling power.  We
changed the code to store them in something like a circular buffer, and
to circulate the bytes regularly. 




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