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1.2 Basic of Information Security
Goals of Security
Prevention
Prevent attackers from violating security policy
Detection
Detect attackers’ violation of security policy
Recovery
Attack is stopped, system is fixed, resume（重新开始）operations
(Advanced Version) Continue to function correctly even if attack succeeds
Trust and Assumptions
Policies（策略）
Correctly capture security requirements
Unambiguously（明确） partition system states
Mechanisms（机制）
Assumed（假定） to enforce policy
Rely on supporting infrastructure（基础设施）
策略：允许什么，禁止什么。
机制：实施安全策略。
2.1 History of Cryptography
The Vigenère Square
One Time Pads（一次性密码本）
2.2 A Brief Introduction To Cryptography
Secret-Key (Symmetric) Cryptography
classic ciphers
substitution ciphers（替换密码）
transposition ciphers（换位密码）
重新编排明文字母顺序，而所有的字母没有改变
product ciphers
use both
block ciphers
DES
Problems with private key ciphers
In order for Alice & Bob to be able to communicate securely using a
private key cipher, such as DES, they have to have a shared key in the first
place.
Alice needs to keep 100 different keys if she wishes to communicate with
信息安全原理
