1.1相关术语

贯穿本单元，我会频繁使用“漏洞”、“威胁”、“攻击”这些词条。而在继续进行之前有必要解释一下这些词：

漏洞（vulnerability）是指一个组件将系统置于可被开放利用的状态（如：一个网络线缆或协议缺陷）

威胁（threat）表示潜在的安全侵害；

攻击（attack）是指一次侵害的尝试；

当你学习完本单元后，应该能够解释下面所有词条：

active attack - 主动攻击

application layer encryption - 应用层加密

application level gateway - 应用层网关

asymmetric key system - 非对称密钥系统

attack - 攻击

authentication - 认证

availability - 可用性

bastion host - 堡垒主机

block cipher - 分组密码

brute force attack - 暴力攻击

Caesar cipher - 凯撒密码

certification authority - 证书机构

ciphertext - 密文

circuit level gateway - 线路级网关

collision-free - 无碰撞

confidentiality - 保密性

cryptanalysis - 密码分析

cryptography

cryptosystem

decryption

demilitarised zone

denial-of-service attacks

digital signature

encryption

end-to-end encryption

filtering rules

firewall

freshness

hash value

integrity

key

keyspace

keystream

link layer encryption

masquerade attack

message authentication code

message digest

message modification

message replay

network layer encryption

nonce

one-time pad

one-way hash function

passive attack

password

password cracker

plaintext

private key

protocol analyser

proxy server

public key

public key infrastructure

public key system

registration authority

screened sub-net

sequence number

session key

shared key system

sniffer

stream cipher

symmetric key system

threat

time stamp

traffic analysis

Trojan

virus

vulnerability

worm