密码编码学与网络安全第四版答案翻译.docx

文档介绍：Document serial number【KKGB-LBS98YT-BS8CB-BSUT-BST108】
密码编码学与网络安全第四版答案翻译
第二章
什么是对称密码的本质成分
Plaintext, encryption algorithm, secret key, ciphertext, decryption algorithm.
明文 加密算法 密钥 密文 解密算法
密码算法中两个基本函数式什么
Permutation and substitution.
代换和置换P20
用密码进行通信的两个人需要多少密钥
对称密码只需要一把，非对称密码要两把P20
分组密码和流密码的区别是什么
A stream cipher is one that encrypts a digital data stream one bit or one byte at a time. A block cipher is one in which a block of plaintext is treated as a whole and used to produce a ciphertext block of equal length.
分组密码每次输入的一组元素，相应地输出一组元素。流密码则是连续地处理输入元素，每次输出一个元素。P20
攻击密码的两种一般方法是什么
Cryptanalysis and brute force.
密码分析和***
列出并简要定力基于攻击者所知道信息的密码分析攻击类型。
Ciphertext only. One possible attack under these circumstances is the brute-force approach of trying all possible keys. If the key space is very large, this becomes impractical. Thus, the opponent must rely on an analysis of the ciphertext itself, generally applying various statistical tests to it.
Known analyst may be able to capture one or more plaintext messages as well as their encryptions. With this knowledge, the analyst may be able to deduce the key on the basis of the way in which the known plaintext is transformed.
Chosen plaintext. If the analyst is able to choose the messages to encrypt, the analyst may deliberately pick patterns that can be expected to reveal the structure of the key.
惟密文