Crypto U2, Crypto design principles

Crypto U2, Crypto design principles

1. large keyspace is necessary

2. possible to break cryptosystem without first determining the key

   • cryptosystem designers must worry about more than the key

3. effective techniques for disguising plaintext

   • increase alphabet sizes
   • ensure that each plaintext letter encrypts to a variety of different ciphertext "letters"
   • introduce positional dependency

4. always a tradeoff between efficiency and security

5. can design for attacks that we know already, but keep watch for new attacks and adapt as needed