Iterating Block ciphers Definition A product cipher combines two or more transformations in a manner intending that the resulting cipher is more secure than the individual components. Definition An iterated block cipher is a block cipher involving the sequential repetition of an internal function called a round function. Parameters include the number of rounds Nr, the block bitsize n, and the bitsize k of the input key K from which Nr subkeys Ki (round keys) are derived. For invertibility (allowing unique decryption), for each value Ki the round function is a bijection on the round input

Originally designed to be efficient in hardware . A LOT of money has been invested in hardware. although DES standard is public there was considerable controversy over design – in choice of 56-bit key (vs Lucifer 128-bit) – and because design criteria were classified

Additional key-sizes and block-sizes Ability to function efficiently and securely in a wide variety of platforms and applications low-end smartcards, wireless: small memory requirements IPSec, ATM – small key setup time in hardware B-ISDN, satellite communication – large encryption speed Flexibility

Cryptographic protocol – Distributed algorithm – Based on cryptographic building blocks – To achieve a security related goal Examples: – Entity Authentication – Key Establishment:Key Distribution(Key enveloping, Key transport), Key agreement – Electronic Payment

6.1 对象指针和对象引用 6.2 对象数组和对象指针数组 6.3 常对象和常成员 6.4 子对象和堆对象

5.1 类的定义 5.2 对象的定义 5.3 对象的初始化 5.4 成员函数的特征

4. 1 函数的定义和说明 4. 2 函数的调用 4.3 函数参数 4.4 内联函数

1. 文件包含命令 使用格式如：#include 《文件名》/″〈文件名〉″ 2. 条件编译命令 3. 宏定义命令

1. 常用的基本数据类型 2. C++语言的基本数据类型表见教材第23页表2. 1

1. 面向对象的由来和发展 面向对象的语言更接近于自然语言。 2. 面向对象语言实现更高级的抽象 面向对象的抽象原理： 数据抽象和行为共享。 3. 面向对象的基本特征 （1） 对象 （2） 类 （3） 继承