《Operating System Concepts》学习第 58 天，p636-p666 总结，总计 31 页。
一、技术总结
1.system and network threats
(1)attack network traffic
(2)denial of service
(3)port scanning
2.symmetric/asymmetric encryption algorithm
(1)symmetric encryption algorithm
A cryptography algorithm in which the same keys are used to encrypt and decrypt the message or data.
(2)asymmetric encryption algorithm
A cipher algorithm in which different keys are used for encryption and decryption.
二、英语总结(生词：3)
1.masquerade
(1)masquerade: maschera(“mask”) + -ade(suffix that indicating an action or process)
c/u. behavior that is intended to prevent truth from being known(掩饰)；vi. to pretend to be(伪装)。
(2)示例
Alternatively, an attacker can take a more active role, either masquerading as one of the parties (referred to as spoofing), or becoming a fully active man-in-the-middle, intercepting and possibly modifying transactions between two peers(《Operating System Concepts》第 636 页)。
2.defense
(1)defend: de-(“away, off”) + fendere(“to strike, hit, push”)
vi/vt. defend literally means to push away an attack(to protect from harm，保护，防卫，捍卫).
(2)defense
u. the act of pretect sth against attack。需要注意用法：defense of, defense against。
(3)示例
He published an essay in defense of the freedom of the press(新闻)。
There are many defenses against computer attacks, running the gamut from methodology to technology(《Operating System Concepts》第 637 页)。
3.ask
(1)be asking for it/trouble(自找麻烦)
However, for applications where security matters, we are asking for trouble if we assume that the source or destination address of a packet reliably determines who sent or received that packet(《Operating System Concepts》第 638 页)。
关于英语的注解同步更新汇总到 https://github.com/codists/English-In-CS-Books 仓库。
三、其它
第 16 章(security)简评：该章节对security领域提纲挈领地的进行了介绍，相对而言较简单，只是个入门。
四、参考资料
1. 编程
(1) Abraham Silberschatz，Peter Baer Galvin，Greg Gagne《Operating System Concepts》：https://book.douban.com/subject/30272539/
2. 英语
(1) Etymology Dictionary：https://www.etymonline.com
(2) Cambridge Dictionary：https://dictionary.cambridge.org
欢迎搜索及关注：编程人(a_codists)
