Example: Design an encryptor
DES
- Input is clear-text (or plain-text)
- Output is cipher-text
- Same algorithm encrypts and decrypts
Details
- IP is initial permutation
- L is left-half of message
- R is right half of message
- 16 iterations on the message
- is XOR
- K are keys
- f is a function (next slide)
- IP–1 is an inverse permutation