Data stored in RAM isn't secure with power removal either.
I saw a case where encryption keys were retained not only after loss of
power, but even after shorting VCC to ground for days, and then powering up
the system and writing to the data area.  When powered down and back up, the
keys re-appeared!

Apparently long term storage in those SRAM cells caused a bias.. If the keys
had been stored a short time you couldn't recover them and if longer times
you'd get partial recovery, but if it was long enough, they'd come back from
the dead.

The problem was soved by keeping the key data on the move in a circular
buffer.
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist