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3.1 (Cryptography History (1300's, Geoffrey Chaucer included several…

- - - - each letter retains its position but changes its identity (confusion)
        
        Monoalphabetic Cipher
        
        Polyalphabetic Cipher (e.g Vigenere Tableau)
        
        Caesar Cipher (shift)
        
        One-Time Pad (e.g Vernam Cipher)
        Advantage: immune to most attacks
        Disadvantages:
        
        Need total synchronization between Sender and Receiver
        
        Need very long key
        
        Key cannot be reused
        
        Key management: printing, storing, accounting
      - Advantages
        
        Simple
        
        Easy to encrypt
      - Disadvantages
        
        Easy to break!!!
    - - each letter retains its identity but changes its position.(diffusion)
        
        columnar transposition
      - Advantages
        
        easy to implement
      - Disadvantages
        
        Easily broken for cipher only attack
        
        Trivially broken for known plaintext attack
    - - Combine both methods
        
        Simple ciphers can be implemented in hardware
        
        One encryption applied to the result of the other
        
        Broken for Chosen plaintext
        
        S-box = substition cipher
        
        P-box = permutation (transposition) cipher across S-boxes inputs
  - - - all block encryption algorithms have a structure first described by Horst Feistel of IBM in 1973
      - Feistel Cipher Structure
        
        most symmetric block ciphers are based on a Feistel Cipher Structure
        
        Feistel Cipher Design Principles
        
        Feistel Network depends on the choice of the following parameters and design features
        
        key size
        
        subkey generation
        
        round function
        
        number of rounds
        
        block size
        
        fast software en/decryption & ease of analysis
      - Advantages and Disadvantages
        
        Diffusion
        
        Immunity to insertions
        
        Slowness of encryption
        
        Error propagation
    - - Advantages and Disadvantages
        
        Speed of transformation
        
        Low error propagation
        
        Low diffusion
        
        Vulnerable to malicious insertion and modification
  - - - Public key cryptography:
    - - Secret key cryptography
    - - Hash functions