Skip to content
Textbook Guides

Solution Manual for Network Security Essentials: Applications and Standards, 6th Edition

Get a deeper understanding of your textbook with Solution Manual for Network Security Essentials: Applications and Standards, 6th Edition, featuring expert solutions to every problem.

Preview 16 of 94 pages

See the first 16 pages exactly as they appear in the document.

  1. Page 1
    Read page 1 as text

    SOLUTIONS MANUAL N ETWORK S ECURITY E SSENTIALS : A PPLICATIONS AND S TANDARDS S IXTH E DITION W ILLIAM S TALLINGS

  2. Page 2
  3. Page 3
    Read page 3 as text

    -4- Chapter 1 Introduction ............................................................. 5 Chapter 2 Symmetric Encryption and Message Confidentiality ....... 11 Chapter 3 Public-Key Cryptography and Message Authentication ... 22 Chapter 4 Key Distribution and User Authentication ..................... 29 Chapter 5 Network Access Control and Cloud Security ................. 38 Chapter 6 Transport-Level Security ........................................... 41 Chapter 7 Wireless Network Security ......................................... 44 Chapter 8 Electronic Mail Security ............................................. 48 Chapter 9 IP Security .............................................................. 53 Chapter 10 Malicious Software.................................................. 60 Chapter 11 Intruders .............................................................. 67 Chapter 12 Firewalls ............................................................... 74 Chapter 13 Network Management Security ................................. 81 Chapter 14 Legal and Ethical Aspects ........................................ 85 Chapter 15 SHA-3 .................................................................. 92 TABLE OF CONTENTS

  4. Page 4
    Read page 4 as text

    -5- C HAPTER 1 I NTRODUCTION A NSWERS TO Q UESTIONS 1.1 The OSI Security Architecture is a framework that provides a systematic way of defining the requirements for security and characterizing the approaches to satisfying those requirements. The document defines security attacks, mechanisms, and services, and the relationships among these categories. 1.2 Passive attacks have to do with eavesdropping on, or monitoring, transmissions. Electronic mail, file transfers, 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. 1.3 Passive attacks: release of message contents and traffic analysis. Active attacks: masquerade, replay, modification of messages, and denial of service. 1.4 Authentication: 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 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, deletion, 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 authorized 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).

  5. Page 5
    Read page 5 as text

    -6- 1.5 See Table 1.3. 1.6 Economy of mechanism: the design of security measures embodied in both hardware and software should be as simple and small as possible. Fail-safe defaults: access decisions should be based on permission rather than exclusion. Complete mediation: every access must be checked against the access control mechanism. Open Design: the design of a security mechanism should be open rather than secret. Separation of privilege: a practice in which multiple privilege attributes are required to achieve access to a restricted resource. Least Privilege: every process and every user of the system should operate using the least set of privileges necessary to perform the task. Least common mechanism: the design should minimize the functions shared by different users, providing mutual security. Psychological acceptability: the security mechanisms should not interfere unduly with the work of users, while at the same time meeting the needs of those who authorize access. Isolation: a principle that applies in three contexts. (1) public access systems should be isolated from critical resources (data, processes, etc.) to prevent disclosure or tampering. (2) the processes and files of individual users should be isolated from one another except where it is explicitly desired. (3) security mechanisms should be isolated in the sense of preventing access to those mechanisms. Encapsulation: a specific form of isolation based on object-oriented functionality. Modularity: refers both to the development of security functions as separate, protected modules and to the use of a modular architecture for mechanism design and implementation. Layering: the use of multiple, overlapping protection approaches addressing the people, technology, and operational aspects of information systems. Least Astonishment: means that a program or user interface should always respond in the way that is least likely to astonish the user. 1.7 An attack surface consists of the reachable and exploitable vulnerabilities in a system. An attack tree is a branching, hierarchical data structure that represents a set of potential techniques for exploiting security vulnerabilities. A NSWERS TO P ROBLEMS

  6. Page 6
    Read page 6 as text

    -7- 1.1 The system must keep personal identification numbers confidential, both in the host system and during transmission for a transaction. It must protect the integrity of account records and of individual transactions. Availability of the host system is important to the economic well being of the bank, but not to its fiduciary responsibility. The availability of individual teller machines is of less concern. 1.2 The system does not have high requirements for integrity on individual transactions, as lasting damage will not be incurred by occasionally losing a call or billing record. The integrity of control programs and configuration records, however, is critical. Without these, the switching function would be defeated and the most important attribute of all - availability - would be compromised. A telephone switching system must also preserve the confidentiality of individual calls, preventing one caller from overhearing another. 1.3 a. The system will have to assure confidentiality if it is being used to publish corporate proprietary material. b. The system will have to assure integrity if it is being used to laws or regulations. c. The system will have to assure availability if it is being used to publish a daily paper. 1.4 a. An organization managing public information on its web server determines that there is no potential impact from a loss of confidentiality (i.e., confidentiality requirements are not applicable), a moderate potential impact from a loss of integrity, and a moderate potential impact from a loss of availability. b. A law enforcement organization managing extremely sensitive investigative information determines that the potential impact from a loss of confidentiality is high, the potential impact from a loss of integrity is moderate, and the potential impact from a loss of availability is moderate. c. A financial organization managing routine administrative information (not privacy-related information) determines that the potential impact from a loss of confidentiality is low, the potential impact from a loss of integrity is low, and the potential impact from a loss of availability is low. d. The management within the contracting organization determines that: (i) for the sensitive contract information, the potential impact from a loss of confidentiality is moderate, the potential impact from a loss of integrity is moderate, and the potential impact from a loss of availability is low; and (ii) for the routine administrative information (non-privacy-related information), the potential impact from a loss of confidentiality is low, the potential impact from a loss of integrity is low, and the potential impact from a loss of availability is low.

  7. Page 7
    Read page 7 as text

    -8- e. The management at the power plant determines that: (i) for the sensor data being acquired by the SCADA system, there is no potential impact from a loss of confidentiality, a high potential impact from a loss of integrity, and a high potential impact from a loss of availability; and (ii) for the administrative information being processed by the system, there is a low potential impact from a loss of confidentiality, a low potential impact from a loss of integrity, and a low potential impact from a loss of availability. Examples from FIPS 199. 1.5 Release of message contents Traffic analysis Masquerade Replay Modification of messages Denial of service Peer entity authentication Y Data origin authentication Y Access control Y Confidentiality Y Traffic flow confidentiality Y Data integrity Y Y Non-repudiation Y Availability Y

  8. Page 8
    Read page 8 as text

    -9- 1.6 Release of message contents Traffic analysis Masquerade Replay Modification of messages Denial of service Encipherment Y Digital signature Y Y Y Access control Y Y Y Y Y Data integrity Y Y Authentication exchange Y Y Y Y Traffic padding Y Routing control Y Y Y Notarization Y Y Y 1.7 Open Safe Pick Lock Threaten Blackmail Eavesdrop Bribe Learn Combination Find Writ- ten Combo Get Combo from Target Listen to Conversation Get Target to State Combo Cut Open Safe Install Improperly

  9. Page 9
    Read page 9 as text

    -10- 1.8 We present the tree in text form; call the company X: Survivability Compromise: Disclosure of X proprietary secrets OR 1. Physically scavenge discarded items from X OR 1. Inspect dumpster content on-site 2. Inspect refuse after removal from site 2. Monitor emanations from X machines AND 1. Survey physical perimeter to determine optimal monitoring position 2. Acquire necessary monitoring equipment 3. Setup monitoring site 4. Monitor emanations from site 3. Recruit help of trusted X insider OR 1. Plant spy as trusted insider 2. Use existing trusted insider 4. Physically access X networks or machines OR 1. Get physical, on-site access to Intranet 2. Get physical access to external machines 5. Attack X intranet using its connections with Internet OR 1. Monitor communications over Internet for leakage 2. Get trusted process to send sensitive information to attacker over Internet 3. Gain privileged access to Web server 6. Attack X intranet using its connections with public telephone network (PTN) OR 1. Monitor communications over PTN for leakage of sensitive information 2. Gain privileged access to machines on intranet connected via Internet

  10. Page 10
    Read page 10 as text

    -11- C HAPTER 2 S YMMETRIC E NCRYPTION AND M ESSAGE C ONFIDENTIALITY A NSWERS TO Q UESTIONS 2.1 Plaintext, encryption algorithm, secret key, ciphertext, decryption algorithm. 2.2 Permutation and substitution. 2.3 One secret key. 2.4 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. 2.5 Cryptanalysis and brute force. 2.6 In some modes, the plaintext does not pass through the encryption function, but is XORed with the output of the encryption function. The math works out that for decryption in these cases, the encryption function must also be used. 2.7 With triple encryption, a plaintext block is encrypted by passing it through an encryption algorithm; the result is then passed through the same encryption algorithm again; the result of the second encryption is passed through the same encryption algorithm a third time. Typically, the second stage uses the decryption algorithm rather than the encryption algorithm. 2.8 There is no cryptographic significance to the use of decryption for the second stage. Its only advantage is that it allows users of 3DES to decrypt data encrypted by users of the older single DES by repeating the key.

  11. Page 11
    Read page 11 as text

    -12- A NSWERS TO P ROBLEMS 2.1 a. 2 8 10 7 9 6 3 1 4 5 C R Y P T O G A H I B E A T T H E T H I R D P I L L A R F R O M T H E L E F T O U T S I D E T H E L Y C E U M T H E A T R E T O N I G H T A T S E V E N I F Y O U A R E D I S T R U S T F U L B R I N G T W O F R I E N D S 4 2 8 10 5 6 3 7 1 9 N E T W O R K S C U T R F H E H F T I N B R O U Y R T U S T E A E T H G I S R E H F T E A T Y R N D I R O L T A O U G S H L L E T I N I B I T I H I U O V E U F E D M T C E S A T W T L E D M N E D L R A P T S E T E R F O ISRNG BUTLF RRAFR LIDLP FTIYO NVSEE TBEHI HTETA EYHAT TUCME HRGTA IOENT TUSRU IEADR FOETO LHMET NTEDS IFWRO HUTEL EITDS b. The two matrices are used in reverse order. First, the ciphertext is laid out in columns in the second matrix, taking into account the order dictated by the second memory word. Then, the contents of the second matrix are read left to right, top to bottom and laid out in columns in the first matrix, taking into account the order dictated by the first memory word. The plaintext is then read left to right, top to bottom. c. Although this is a weak method, it may have use with time-sensitive information and an adversary without immediate access to good cryptanalysis (e.g., tactical use). Plus it doesn't require anything more than paper and pencil, and can be easily remembered.

  12. Page 12
    Read page 12 as text

    -13- 2.2 a. Let –X be the additive inverse of X. That is –X + X = 0. Then: P = (C + –K 1 ) ⊕ K 0 b. First, calculate –C'. Then –C' = (P' ⊕ K 0 ) + (–K 1 ). We then have: C + –C' = (P ⊕ K 0 ) + (P' ⊕ K 0 ) However, the operations + and ⊕ are not associative or distributive with one another, so it is not possible to solve this equation for K 0 .

  13. Page 13
    Read page 13 as text

    -14- 2.3 a. The constants ensure that encryption/decryption in each round is different. b. First two rounds: Delta 1 K 0 L 0 L 1 L 2 R 2 R 0 R 1 K 1 < < 4 > > 5 Delta 2 K 2 K 3 < < 4 > > 5

  14. Page 14
    Read page 14 as text

    -15- c. First, let's define the encryption process: L 2 = L 0 + [(R 0 << 4) + K 0 ] ⊕ [R 0 + δ 1 ] ⊕ [(R 0 >> 5) + K 1 ] R 2 = R 0 + [(L 2 << 4) + K 2 ] ⊕ [L 2 + δ 2 ] ⊕ [(L 2 >> 5) + K 3 ] Now the decryption process. The input is the ciphertext (L 2 , R 2 ), and the output is the plaintext (L 0 , R 0 ). Decryption is essentially the same as encryption, with the subkeys and delta values applied in reverse order. Also note that it is not necessary to use subtraction because there is an even number of additions in each equation. R 0 = R 2 + [(L 2 << 4) + K 2 ] ⊕ [L 2 + δ 2 ] ⊕ [(L 2 >> 5) + K 3 ] L 0 = L 2 + [(R 0 << 4) + K 0 ] ⊕ [R 0 + δ 1 ] ⊕ [(R 0 >> 5) + K 1 ]

  15. Page 15
    Read page 15 as text

    -16- d. Delta 1 K 0 L 0 L 1 L 2 R 2 R 0 R 1 K 1 < < 4 > > 5 Delta 2 K 2 K 3 < < 4 > > 5 2.4 To see that the same algorithm with a reversed key order produces the correct result, consider Figure 2.2, which shows the encryption process going down the left-hand side and the decryption process going up the right-hand side for a 16-round algorithm (the result would be the same for any number of rounds). For clarity, we use the notation LE i and RE i

  16. Page 16
    Read page 16 as text

    -17- for data traveling through the encryption algorithm and LD i and RD i for data traveling through the decryption algorithm. The diagram indicates that, at every round, the intermediate value of the decryption process is equal to the corresponding value of the encryption process with the two halves of the value swapped. To put this another way, let the output of the ith encryption round be LE i ||RE i (L i concatenated with R i ). Then the corresponding input to the (16 – i)th decryption round is RD i ||LD i . Let us walk through the figure to demonstrate the validity of the preceding assertions. To simplify the diagram, it is unwrapped, not showing the swap that occurs at the end of each iteration. But note that the intermediate result at the end of the ith stage of the encryption process is the 2w-bit quantity formed by concatenating LE i and RE i , and that the intermediate result at the end of the ith stage of the decryption process is the 2w-bit quantity formed by concatenating LD i and RD i . After the last iteration of the encryption process, the two halves of the output are swapped, so that the ciphertext is RE 16 ||LE 16 . The output of that round is the ciphertext. Now take that ciphertext and use it as input to the same algorithm. The input to the first round is RE 16 ||LE 16 , which is equal to the 32-bit swap of the output of the sixteenth round of the encryption process. Now we would like to show that the output of the first round of the decryption process is equal to a 32-bit swap of the input to the sixteenth round of the encryption process. First, consider the encryption process. We see that: LE 16 = RE 15 RE 16 = LE 15 ⊕ F(RE 15 , K 16 ) On the decryption side: LD 1 = RD 0 = LE 16 = RE 15 RD 1 = LD 0 ⊕ F(RD 0 , K 16 ) = RE 16 ⊕ F(RE 15 , K 16 ) = [LE 15 ⊕ F(RE 15 ,K 16 )] ⊕ F(RE 15 , K 16 ) The XOR has the following properties: [A ⊕ B] ⊕ C = A ⊕ [B ⊕ C] D ⊕ D = 0 E ⊕ 0 = E Thus, we have LD 1 = RE 15 and RD 1 = LE 15 . Therefore, the output of the first round of the decryption process is LE 15 ||RE 15 , which is the 32- bit swap of the input to the sixteenth round of the encryption. This

78 more pages in the full document

Unlock it once and it stays in your library, ready to chat with or turn into flashcards.

Unlock the full document

More Information Technology study materials

See all

Study this document with CramX

Once it is in your library, every tool can work from it.