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
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- 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