Simple methods

• Caesar Cipher (K=3)
  
  

      Plaintext:  ATTACK AT DAWN    K=1
      Ciphertext: BUUBDLABUAEBXO
          

  
  
• Vigenere Cipher

      Key       : A B C A B C A B C
      Plaintext : A T T A C K   A T
      Ciphertext: B V W B E N A C W
          

• Vernam Cipher (one time pad)
  • 
  • Key as long as plaintext
  • The Only Secure System
• Binary file
  
• Encryption/Decryption Machine (Hardware)