One lesson I plan to observe - don't encrypt known plaintext unless you have to !
The EFF DES Cracker cracks more than just known plaintext (though it's the easy case). It also cracks plaintexts whose likely byte values are known (e.g. all alphanumeric), winnowing the keyspace down to a size that software or humans can search. Such a search runs in very close to the time required for an ordinary known-plaintext search. See the book for details (www.oreilly.com). We successfully cracked a DES-encrypted Eudora saved-mail file provided by Bruce Schneier during our debugging period. He gave us the top byte of the key so we could focus on debugging rather than on waiting to get to the right block of keyspace. The machine located the key within that 49-bit keyspace after we fixed a few software bugs. John