Inside DES #1

nBlock
cipher

n64 bits of
data (In/Out)

n56 bits of key
(7x1016)

n16 Rounds

¨XOR left 32
bits with Fiestel
function (F) of right 32
bits and 48 bits of subkey

¨Swap left 32
and right 32 bits

nDecrypt by
same process but
with subkeys in reverse
order

One round of the DES
cipher