Also, can your tool use floppies instead of USB keys?
It's a freakin' C program that works on a file - but carrying a floppy around is so ... ordinary.
There are problems with KGB-quality attackers recovering overwritten data which are probably much more serious for disks than flash rom, but they're nearly universal and good shredders work well on them.
Bits are overwritten by running PRNG output on them 128 times, PRNG being seeded by the data that has just been erased. We use DES in counter mode as PRNG.
You need to use each bit twice - once to encrypt, and once to decrypt. Destroying them after the first use is a bad idea....
Why would sender need to decrypt known plaintext is beyond me ... sender XORs and destroys bits, recipient XORs and destroys bits. Each in their respective dongles, once. ===== end (of original message) Y-a*h*o-o (yes, they scan for this) spam follows: Y! Web Hosting - Let the expert host your web site http://webhosting.yahoo.com/