密码编码学与网络安全(第五版)答案.docx

1、Chapter 1:Introduction5Chapter 2:Classical Encryption Techniques7Chapter 3:Block Ciphers and the Date Encryption Standard13Chapter 4:Finite Fields21Chapter 5:Advanced Encryption Standard28Chapter 6:More on Symmetric Ciphers33Chapter 7:Confidentiality Using Symmetric Encryption38Chapter 8:Introductio

2、n to Number Theory42Chapter 9:Public-Key Cryptography and RSA46Chapter 10:Key Management; Other Public-Key Cryptosystems55Chapter 11:Message Authentication and Hash Functions59Chapter 12:Hash and MAC Algorithms62Chapter 13:Digital Signatures and Authentication Protocols66Chapter 14:Authentication Ap

3、plications71Chapter 15:Electronic Mail Security73Chapter 16:IP Security76Chapter 17:Web Security80Chapter 18:Intruders83Chapter 19:Malicious Software87Chapter 20:Firewalls89Answers to Questions1.1The OSI Security Architecture is a framework that provides a systematic way of defining the requirements

4、 for security and characterizing the approaches to satisfying those requirements. The document defines security attacks, mechanisms, and services, and the relationships among these categories.1.2Passive attacks have to do with eavesdropping on, or monitoring, transmissions. Electronic mail, file tra

5、nsfers, and client/server exchanges are examples of transmissions that can be monitored. Active attacks include the modification of transmitted data and attempts to gain unauthorized access to computer systems.1.3Passive attacks: release of message contents and traffic analysis. Active attacks: masq

6、uerade, replay, modification of messages, and denial of service.1.4Authentication: The assurance that the communicating entity is the one that it claims to be. Access control: The prevention of unauthorized use of a resource (i.e., this service controls who can have access to a resource, under what

7、conditions access can occur, and what those accessing the resource are allowed to do). Data confidentiality: The protection of data from unauthorized disclosure. Data integrity: The assurance that data received are exactly as sent by an authorized entity (i.e., contain no modification, insertion, de

8、letion, or replay). Nonrepudiation: Provides protection against denial by one of the entities involved in a communication of having participated in all or part of the communication. Availability service: The property of a system or a system resource being accessible and usable upon demand by an auth

9、orized system entity, according to performance specifications for the system (i.e., a system is available if it provides services according to the system design whenever users request them). 1.5See Table 1.3.Answers toProblems1.1Release of message contentsTraffic analysisMasqueradeReplayModification

10、 of messagesDenial of servicePeer entity authenticationYData origin authenticationYAccess controlYConfidentialityYTraffic flow confidentialityYData integrityYYNon-repudiationYAvailabilityY1.2Release of message contentsTraffic analysisMasqueradeReplayModification of messagesDenial of serviceEncipherm

11、entYDigital signatureYYYAccess controlYYYYYData integrityYYAuthentication exchangeYYYYTraffic paddingYRouting controlYYYNotarizationYYYChapter 2Classical Encryption TechniquesrAnswers to Questions2.1Plaintext, encryption algorithm, secret key, ciphertext, decryption algorithm.2.2Permutation and subs

12、titution.2.3One key for symmetric ciphers, two keys for asymmetric ciphers.2.4A 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.2.5

13、Cryptanalysis and brute force.2.6Ciphertext 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

14、various statistical tests to it. Known plaintext. The 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 t

15、he 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.2.7An encryption scheme is unconditionally secure if the ciphertext generated by the scheme does not contain enough information to determine uniquely the corresponding plaintext, no matter how much ciphertext i