Introduction

Cryptography -> Network Security -> Ethical and Legal Issue

Classical Encryption Techniques

• Substitution Ciphers
• Transposition Ciphers
• One-Time Pad
• Rotor Machine

Secret Key Cryptography

• 雙方的 key 相同。
• Block Ciphers
  
  
  • Example
    • FEAL, IDEA
    • RC5, RC6
    • Skipjack
    • CAST Blowfish
    • AES
    • DES, TripleDES, Lucifer
  • Modes of operation
    • ECB (Electronic CodeBook)
    • CBC(Cipher Block Chaining)
    • CFB(CipherFeedBack)
    • OFB(Output FeedBack)
    • CTR（Counter)
    • XTS-AES
  • AEAD (authenticated encryption with associated data)
    • 同時認證與加密
• Stream Cipher