(Test Bank) Cryptography and Network Security Principles and Practice

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Cryptography and Network Security: Principles and Practice, 8th Edition, by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. CHAPTER 1: COMPUTER AND NETWORK SECURITY CONCEPTS TRUE OR FALSE T F 1. The OSI security architecture focuses on security attacks, mechanisms, and services. T F 2. Security attacks are classified as either passive or aggressive. T F 3. Cybersecurity strives to ensure the attainment and maintenance of the security properties of the organization and users’ assets against relevant security risks in the cybe rspace environment . T F 4. Information security and network security are subsets of cybersecurity. T F 5. Data authenticity assures that priv ate or confidential information is not made available or disclosed to unauthorized individuals. T F 6. The OSI security archi tecture focuses on security attacks, mechanisms, and services. T F 7. An active attack attempts to alter system resources or affect their operation. T F 8. Authentication exchange is the use of a trusted third party to assure certain properties of a data exchange. T F 9. A loss of integrity is the unauthorized modification or destruction of information. T F 10. The emphasis in dealing with active attacks is on preve ntion rather than detection. T F 11. The connection-oriented integrity service addresses both message stream modification and denial of service. T F 12. The denial of service prevents or inhibits the normal use or management of communication facilities. T F 13. Integrity can apply to a stream of messages, a single message, or (Test Bank, Answer at the end of each Chapter)Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. selected fields within a message. T F 14. Passive attacks are very easy to detect because they involve alteration of the data. T F 15. Security services implement security policies and are implemented by security mechanisms. MULTIPLE CHOICE 1. _____________ is the collection of tools, policies, security concepts, security safeguards, guidelines, risk management approaches, actions, training, best practices, assurance, and technologies that can be used to protect the cyberspace environment and organization an d users’ assets. A) Access control B) Data authenticity C) Cybersecurity D) Authentication 2. A common technique for masking contents of messages or other information traffic so that opponents can not extract the information from the message is __________ . A) integrity B) encryption C) analysis D) masquerade 3. __________ involves the passive capture of a data unit and its subsequent retransmission to produce an unauthorized effect. A) Disruption B) Replay C) Service denial D) Masquerade 4. _________ is a branch of mathematics that deals with the transformation of data. A) Cryptography B) Modularity Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. C) Encapsulation D) Encryption 5. A loss of __________ is the unauthorize d disclosure of information. A) authenticity B) confidentiality C) reliability D) integrity 6. Verifying that users are who they say they are and that each input arriving at the system came from a trusted source is _________ . A) authenticity B) credibility C) accountability D) integrity 7. A _________ is a value computed with a cryptogr aphic algorithm and associated with a data object in such a way th at any recipient of the data can use the signature to verify the data’s origin and integrity. A) key exchange B) digital signature C) message authentication code D) notarization 8. A __________ is any action that compromises the security of informatio n owned by an organization. A) security attack B) security service C) security alert D) security mechanism 9. A __________ takes place when one entity preten ds to be a different entity. A) replay B) masquerade C) service denial D) passive attack 10. __________ is the protection of transmitte d data from passive attacks. Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. A) Access control B) Data control C) Nonrepudiation D) Confidentiality 11. A(n) __________ service is one that protects a system to ensure its availability and addresses the security concerns raised by denial -of-service attacks. A) replay B) availability C) masquerade D) integrity 12. Two types of __________ attacks are the release of message contents and traffic analysis. A) information B) eavesdropping C) service D) passive 13. A(n) __________ is any circumstance or event with the potential to adversely impact organizational operations (including mission, functions, image, or reputation), organizational assets, individuals, other organizations, or the Nation through an information system via unauth orized access, destruction, disclosure, modification of information, and/or denial of service. A) threat B) attack C) risk D) attack vector 14. A __________ is a hardware and/or software capability that limits access between a network and device at tached to the network, in accordance with a specific security policy. A) trust model B) cryptographic algorithm C) firewall D) router Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. 15. Data appended to, or a cryptographic transformation of, a data unit that allows a recipient of the data unit to prove the source and integrity of the data unit and protect against forgery is a(n) ___________ . A) security audit trail B) digital signature C) encipherment D) authentication exchange SHORT ANSWER 1. The general security objectives of cybersecuri ty comprise the following: availability; integrity, which may include data authenticity and nonrepudiation; and __________ . 2. A ______________ is a process (or a device incorporating such a process) that is designed to detect, prevent, or recover from a s ecurity attack. 3. An ___________ is any kind of malicious activity that attempts to collect, disrupt, deny, degrade, or destroy information system resources or the information itself. 4. A __________ attack attempts to learn or make use of information from the system but does not affect system resources. 5. The emphasis in dealing with __________ attacks is on prevention rather than detection. 6. Active attacks can be subdivided into four categories: replay, __________ , modification of message s, and denial of service. 7. __________ prevents either sender or receiver from denying a transmitted message. 8. __________ is 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. 9. __________ is the insertion of bits into gaps in a data stream to frustrate traffic analysis attempts. Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. 10. Digital __________ is data appended to, or a cryptographic transformation of, a data unit that allows a recipient of the data unit to prove the source and integrity of the data unit and protect against forgery. 11. Cryptographic algorithms can be divided into three categories: keyless, __________ , and two -key. 12. A __________ number generator produces a determi nistic sequence of numbers or bits that has the appearance of being a truly random sequence. 13. Encryption algorithms that use a single key are referred to as ___________ encryption algorithms. 14. __________ is a measure of the extent to which an entity is threatened by a potential circumstance or event, and typically a function of 1) the adverse impacts that would arise if the circumstance or event occurs; and 2) the likelihood of occurrence. 15. __________ is a characteristic of an entity that reflects the de gree to which that entity is deserving of trust. Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. CHAPTER 2 : INTRODUCTION TO NUMBER THEORY TRUE OR FALSE T F 1. The algorithm credited to Euclid for easily finding the greatest common divisor of two integers has broad significance in cryptography. T F 2. Unlike ordinary addition, there is not an additive inverse to each integer in modular arithmetic. 
 T F 3. The scheme where you can f ind the greatest common divisor of two integers by repetitive application of the division algorithm is known as the Brady algorithm. 
 T F 4. Two integers a and b are said to be congruent modulo n, if (a mod n) = ( b mod n). 
 T F 5. Basic concepts from number theory that are needed for understanding finite fields include divisibility, the Euclidian algorithm, and modular arithmetic . T F 6. If b|a we say that b is a divisor of a. T F 7. The notation a|b is commonly used to mean b divides a. 
 T F 8. The rules for ordinary arithmetic involving addition, subtraction, and multiplication carry over into modular arithmetic. 
 T F 9. Two theorems that play important roles in public -key cryptography are Fermat’s theorem and Euler’s theorem . 
 T F 10. One of the useful features of the Chinese remainder theorem is that it provides a way to manipulate potentially very large numbers mod M in terms of tuples of smaller numbers . T F 11. For many cryptographic algorithms, it is necessary to select one or more very large prime numbers. T F 12. The Chinese Remainder Theorem is believed to have been discovered by the Chinese mathematician Agrawal in 100 A.D . Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. T F 13. The primitive roots for the prime number 19 are 2, 3, 10, 13, 14 and 15. T F 14. The first assertion of the CRT, concerning arithmetic operations, follows from the rules for modular arithmeti c. T F 15. All integers have primitive roots. MULTIPLE CHOICE 1. An integer p >1 is a _________ number if and only if its only divisors are + 1 and + p. A) 
prime 
 B) 
composite C) 
indexed 
 D) 
positive 2. Two integers are __________ if their only common positive integer factor is 1. 
 A) 
relatively prime 
 B) 
congruent modulo C) 
polynomials 
 D) 
residual 3. The __________ of two numbers is the largest integer that divides both numbers. A) 
greatest common divisor 
 B) 
prime polynomial C) 
lowest common divisor 
 D) 
integral divisor 4. An important quantity in number theory referred to as __________ is defined as the number of positive integers less than n and relatively prime to n. A) 
CRT 
 B) 
Miller -Rabin 
 C) 
Euler’s totient function 
 D) 
Fermat’s theorem Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. 5. Prime numbers play a __________ role in number theory. A) 
minor B) 
nonessential C) 
critical 
 D) 
abbreviated 6. If p is prime and a is a positive integer, then ap = a (mod p) is an alternative form of _________ theorem. A) 
Rijndael’s 
 B) 
Vignere’s 
 C) 
Euler’s 
 D) 
Fermat’s 7. Two numbers are relatively prime if they have ________ prime factors in common. A) 
some
 B) 
no 
 C) 
multiple 
 D) 
all 8. For given integers a and b, the extended __________ algorithm not only calculates the greatest common divisor d but also two additional integers x and y. 
 A) 
modular 
 B) 
Euclidean 
 C) 
associative 
 D) 
cyclic 9. The proc edure TEST takes a candidate integer n as input and returns the result __________ if n is definitely not a prime. 
 A) 
discrete 
 B) 
composite C) 
inconclusive 
 D) 
primitive 10. If a number is the highest possible exponent to which a number can belong, it is Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. referred to as a _________ of n. A) 
primitive root 
 B) 
composite 
 C) 
discrete logarithm 
 D) 
bijection 11. For any integer b and a primitive root a of prime number p we can find a unique exponent i. This exponent i is referred to as the ___________ . A) 
order 
 B) discrete logarithm 
 C) 
bijection 
 D) 
primitive root 12. Discrete logarithms are fundamental to a number of public -key algorithms including __________ key exchange and the DSA. A) 
Diffie -Hellman 
 B) 
Rijndael -Fadiman C) 
Fermat -Euler
 D) 
Miller -Rabin 13. The congruence relation is used to define __________ . 
 A) 
finite groups 
 B) 
greatest common divisor C) 
lowest common divisor 
 D) 
residue classes 14. As a _________ relation, mod expresses that two arguments have the same remainder with respect to a given modulus. 
 A) 
finite 
 B) 
monic 
 C) 
congruence 
 D) 
cyclic Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. 15. A one -to-one correspondence is called __________. 
 A) 
a bijection 
 B) 
an inclusive C) 
an index 
 D) 
a composite SHORT ANSWER 1. The remainder r in the division algorithm is ofte n referred to as a __________ . 2. One of the basic techniques of number theory is the __________ algorithm which is a simple procedure for determining the greatest common divisor of two positive integers. 
 3. If a is an i nteger and n is a positive integer, we defi ne a mod n to be the remainder when a is divided by n. The integer n is called the __________ . 
 4. Two theorems that play important roles in public -key cryptography are Fermat's theorem and __________ theorem. 5. 
__________ theorem states the following: If p is prime and a is a positive integer not divisible by p, then ap-1 = 1(mod p). 6. 
Two numbers are __________ if their greatest common divisor is 1. 7. The number of positive integers less than n and relatively prime to n is referred to as __________ function. 8. The __________ theorem states that it is possible to reconstruct integers in a certain range from their residues modulo a set of pairwise relatively prime moduli. 
 9. Two integers are relatively _________ if and only if their only common positive Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. integer f actor is 1. 
 10. Discrete logarithms are fundamental to the digital signature algorithm (DSA) and the _________ algorithm. 11. The _________ of a number is defined to be the power to which some positive base (except 1) must be raised in order to equal the nu mber. 12. Two numbers are relatively prime if their greatest common divisor is ______. 13. An integer p > 1 is a __________ number if and only if its only divisors are + 1 and + p. 14. Although it does not appear to be as efficient as the Miller -Rabin algorithm, in 2002 a relatively simple deterministic algorithm that efficiently determines whether a given large number is a prime was developed. This algorithm is known as the _________ algorithm 15. ____________ have the following properties: 1. a = b (mod n) if n| (a - b) 2. a = b (mod n) implies b = a (mod n) 3. a = b (mod n) and b = c (mod n) imply a = c (mod n) Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. CHAPTER 3 : CLASSICAL ENCRYPTION TECHNIQUES TRUE OR FALSE T F 1. Symmetric encryption remains by far the most widely used of the two types of encryption. T F 2. Rotor machines are sophisticated precomputer hardware devices that use substitution techniques. T F 3. Symmetric encryption is a form of cryptosystem in which encryption and decryption are performed using different keys. It is also known as non -conventional encryption. T F 4. With the use of symmetric encryption, the principal security problem is maintaining the secre cy of the key. T F 5. The process of converting from plaintext to ciphertext is known as deciphering or decryption. T F 6. The algorithm will produce a different output depending on the specific secret key being used at the time. The exact substitutions and transformations performed by the algorithm depend on the key. T F 7. When using symmetric encryption it is very important t o keep the algorithm secret. T F 8. On average, half of all possible keys must be tried to achieve success with a brute -force attack. T F 9. Ciphertext generated using a computationally secure encryption scheme is impossible for an opponent to decrypt simply because the required information is not there. T F 10. Monoalphabetic ciphers are easy to break because they reflect the frequency data of the original alphabet. T F 11. As with Playfair, the strength of the Hill cipher is that it completely hide s single letter frequencies. T F 12. A scheme known as a one -time pad is unbreakable because it produces random output that bears no statistical relationship to Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. the plaintext. T F 13. The one -time pad has unlimited utility and is us eful primarily for high -bandwidth channels requiring low security. T F 14. The most widely used cipher is the Data Encryption Standard. T F 15. Steganography renders the message unintelligible to outsiders by various transformations of the text. MULTIPLE CHOICE 1. __________ techniques map plaintext elements (characters, bits) into ciphertext elements. A) Transposition B) Substitution C) Traditional D) Symmetric 2. Joseph Mauborgne proposed an improvement to the Vernam cipher that uses a random key that is as long as the message so that the key does not need to be repeated. The key is used to encrypt and decrypt a single message and then is discarded. Each new message requires a new key of the same length as the new mess age. This scheme is known as a(n) __________ . A) pascaline B) one -time pad C) polycipher D) enigma 3. An original intelligible message fed into the algorit hm as input is known as _______ __ , while the coded message produced as output is called the __________ . A) decryption, encryption B) plaintext, ciphertext C) ciphertext, plaintext D) encryption, decryption 4. Restoring the plaintext from th e ciphertext is __________ . A) deciphering B) transposition Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. C) steganography D) encryption 5. A __________ attack involves trying every possible key until an intelligible translation of the ciphertext is obtained. A) brute -force B) Caesar attack C) ciphertext only D) chosen plaintext 6. Techniques used for deciphering a message without any knowledge of the enciphering details is ___________ . A) blind deciphering B) steganography C) cryptanalysis D) transposition 7. The ___________ takes the ciphertext and the secret key and produces the original plaintext. It is essentially the encryption algorithm run in reverse. A) Voronoi algorithm B) decryption algorithm C) cryptanalysis D) diagram algorithm 8. If both sender and receiver use the same key, t he system is referred to as: A) publi c-key encryption B) two -key C) asymmetric D) conventional encryption 9. __________ attacks exploit the characteristics of the algorithm to attempt to deduce a specific plaintext or to deduce the key being used. A) Brute -force B) Cryptanalytic C) Block cipher D) T ransposition 10. The __________ was used as the standard field system by the British Army in World War I and was used by the U.S. Army and other Allied forces during World War II. A) Caesar cipher B) Playfair cipher C) Hill cipher D) Rail Fence cipher Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. 11. The __________ attack is the easiest to defend against because the opponent has the least amount of information to work with. A) ciphertext -only B) chosen ciphertext C) known plaintext D) chosen plaintext 12. _________ refer to common two -letter combinati ons in the English lang uage. A) Streaming s B) Transposition s C) Digrams D) Polyalphabetic cipher s 13. A way to improve on the simple monoalphabetic technique is to use different monoalphabetic substitutions as one proceeds through the plaintext message. The general name for this approach is ___________ . A) rail fence cipher B) cryptanalysis C) polyalphabetic substitution cipher D) polyanalysis cipher 14. A technique referred to as a __ ________ is a mapping achieved by performing some sort of permutation on the plaintext letters. A) transposition cipher B) polyalphabetic cipher C) Caesar cipher D) monoalphabetic cipher 15. The methods of __________ conceal the existence of t he message in a graphic image. A) steganography B) decryptology C) cryptology D) cryptography SHORT ANSWER 1. __________ encryption is a form of cryptosystem in which encryption and decryption are performed using the same key. Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. 2. A technique for hiding a secret message within a larger document or picture in such a way that others cannot discern the presence or contents of the hidden message is __________ . 3. An encryption scheme is said to be __________ if the cost of breaki ng the cipher exceeds the value of the encrypted information and the time required to break the cipher exceeds the useful lifetime of the information. 4. The two types of attack on an encryption algorithm are cryptanalysis , based on properties of the encryption algorithm, and _________ which involves trying all possible keys. 5. Cryptographic systems are characterized along three independent dimensions: the type of operations used for transfo rming plaintext to ciphertext; the way in which the plaintext is processed; and __________ . 6. All encryption algorithms are based on two general principles: substitution and ____________ . 7. One of the simplest and best known polyalphabetic ciphers is _________ cipher. In this scheme, the set of related monoalphabetic substitution rules consists of the 26 Caesar ciphers with shifts of 0 through 25. Each cipher is denoted by a key letter which is the ciphertext letter that substitutes for the plaintext letter a. 8. A __________ c ipher processes the input one block of elements at a time , producing an output block for each input block , whereas a stream cipher processes the input elements continuously , producing output one element at a time. 9. An encryption scheme is __________ se cure if the ciphertext generated by the scheme does not contain enough information to determine uniquely the corresponding plaintext, no matter how much ciphertext is available. 10. The earliest known , and simplest use , of a substitution cipher was called the __________ cipher and involved replacing each letter of the alphabet with the letter standing three places further down the alphabet. 11. The best known multiple letter encryption cipher is the __________ , which treats digrams in the plaintext as single units and translates these units into ciphertext digrams. 12. The task of making large quantities of random keys on a regular basis and distributing a key of equal length to both sender and receiver for every message sent are difficulties of the __________ scheme. Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. 13. The simplest transposition cipher is the _________ technique , in which the plaintext is written down as a sequence of diagonals and then read off as a sequence of rows. 14. The most widely used cip her ever is the __________ . 15. The __________ consist of a set of independently rotating cylinders through which electrical pulses can flow. Each cylinder has 26 input pins and 26 output pins with internal wiring that connects each input pin to a unique output pin. Cryptography and Network Secur ity: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. CHAPTER 4 : BLOCK CIPHERS AND THE DATA ENCRYPTION STANDARD TRUE OR FALSE T F 1. The vast majority of network based symmetric cryptographic application s make use of stream ciphers. T F 2. The Feistel cipher structure, based on Shannon's proposal of 1945, dates back over a quarter of a century and is the structure used by many significant symmetric block ciphers currently in use. 
 T F 3. DES uses a 56 -bit block and a 64 -bit key. 
 T F 4. If the bit -stream generator is a key -controlled algorithm the two users only need to share the generating key and then each can produce the keystream. 
 T F 5. A problem with the ideal block cipher using a small block siz e is that it is vulnerable to a statisti cal analysis of the plaintext. T F 6. Confusion seeks to make the statistical relationship between the plaintext and ciphertext as complex as possible in order to thwart attempts to deduce the key. T F 7. All other things being equal, smaller block sizes mean greater security. T F 8. Greater complexity in the subkey generation algorithm should lead to greater difficulty of cryptanalysis. T F 9. Fast software encryption/decryption and ease of analysis are two considerations in the design of a Feistel cipher. 
 T F 10. A prime concern with DES has been its vulnerability to brute -force attack because of its relatively short key length. 
 T F 11. One criterion for an S -box is: "If two inputs to an S -box differ in exactly one bit, the outputs must also differ in exactly one bit. “
 T F 12. The heart o f a Feistel block cipher is the function F, which relies on the use of S -boxes. 
 Cryptography and Network Secur ity: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. T F 13. The strict avalanche criterion and the bit independence criterion appear to weaken the effectiveness of the confusion function. 
 T F 14. An advantage of key -dependent S -boxes is that because they are not fixed, it is impossible to analyze the S -boxes ahead of time to look for weaknesses. 
 T F 15. The key schedule algorithm is more popular and has received more attention than S -box design. 
 MULTIPLE CHOICE 1. DES exhibits the classic __________ block cipher structure, which consists of a number of identical rounds of processing. A) 
Feistel 
 B) 
SAC 
 C) 
Shannon 
 D) 
Rendell 2. A sequence of plaintext elements is replaced by a __________ of that sequence which means that no elements are added, deleted or replaced in the sequence, but rather the order in which the elements appear in the sequence is changed. A) 
permutation 
 B) 
diffusion 
 C) 
stream 
 D) 
substitution 3. A __________ cipher is one that encrypts a digital data stream one bit or one byte at a time. A) 
product 
 B) 
block 
 C) 
key 
 D) 
stream 4. The vast majority of network -based symmetric cryptographic applications make use of ________ ciphers. A) 
linear 
 B) block C) 
permutation 
 D) 
stream Cryptography and Network Secur ity: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. 5. A __________ cipher is one in which a block of plaintext is treated as a whole and used to pr oduce a ciphertext block of equal length. A) 
bit 
 B) 
product 
 C) 
stream 
 D) 
block 6. __________ is when each plaintext element or group of elements is uniquely replaced by a corresponding ciphertext element or group of elements. A) 
Substitution 
B) 
Diffusion 
 C) 
Streaming 
 D) 
Permutation 7. Key sizes of __________ or less are now considered to be inadequate. A) 
128 bits 
 B) 
32 bits 
 C) 
16 bits 
 D) 
64 bits 8. Feistel proposed that we can approximate the ideal block cipher by utilizing the concept of a __________ cipher, which is the execution of two or more simple ciphers in sequence in such a way that the final result or product is cryptographically stronger than any of the component ciphers. A) 
linear 
 B) 
permutation 
 C) 
differential 
 D) 
product 9. The criteria used in the design of the ________ __ focused on the design of the S-boxes and on the P function that takes the output of the S -boxes. A) 
Avalanche Attack 
 B) 
Data Encryption Standard C) 
Product Cipher 
 D) 
Substitution Key 10. The greater the number of rounds, the __________ it is to perform cryptanalysis. 
 Cryptography and Network Secur ity: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. A) 
easier 
 B) 
less difficult C) 
equally difficult 
 D) 
harder 11. The function F provides the element of __________ in a Feistel cipher. 
 A) 
clarification 
 B) 
alignment 
 C) 
confusion 
 D) 
stability 12. One of the most intense areas of research in the field of symmetric block ciphers is __________ design. A) 
S-box 
 B) 
F-box 
 C) 
E-box 
 D) 
D-box 13. Mister and Adams proposed that all linear combinations of S -box columns should b e _________ which are a special class of Boolean functions that are highly nonlinear according to certain mathematical criteria. 
 A) 
horizontal functions 
 B) 
angular functions C) 
bent functions 
 D) 
vertical functions 14. The Nyberg approach that is more or less a manual approach with only simple mathematics to support it is __________ . 
 A) 
human -made 
 B) 
random C) 
math -made 
 D) 
random with testing 15. Allowing for the maximum number of possible encryption mappings from the plaintext block is referred to by Feistel as the __________ . 
 A) 
ideal substitution cipher 
 B) 
round function C) 
ideal block cipher 
 D) 
diffusion cipher SHORT ANSWER Cryptography and Network Secur ity: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. 1. A _________ is an encryption/decryption s cheme in which a block of plaintext is treated as a whole and used to produce a ciphertext block of equal length. 
 2. 
__________ seeks to make the relationship between the statistics of the ciphertext and the value of the encryption key as complex as possible so that even if the attacker can get some handle on the statistics of the ciphertext, the way in which the key was used to produce that ciphertext is so complex it is difficult to deduce the key. 
 3. Many block ciphers have a __________ structure which consists of a number of identical rounds of processing and in each round a substitution is performed on one half of the data being processed, followed by a permutation that interchanges the two halves. 
 
 4. Feistel’s is a practical applicat ion of a proposal by Claude Shannon to develop a product ci pher that al ternates confusion and ________ functions . 5. The __________ criterion is defined as: "An S-box satisfies GA of order y if, for a 1-bit input change, at least y output bits change." 
 6. In ___________ the statistical structure of the plaintext is dissipated into long - range statistics of the ciphertext. This is achieved by having each plaintext digit affect the value of many ciphertext digits. 7. The most widely used encryption scheme is ba sed on the __________ adopted in 1977 by the National Bureau of Standards as Federal Information Processing Standard 46. 
 8. A change in one bit of the plaintext or one bit of the key should produce a change in many bits of the ciphertext. This is referred to as the __________ effect. 
 9. Two areas of concern regarding the level of security provided by DES are the nature of the algorithm and the __________ . 
 10. A _________ attack exploits the fact that an encryption or decryption algorithm often takes sligh tly different amounts of time on different inputs. 
 11. The __________ criterion states that output bits j and k should change independently when any single input bit i is inverted for all i, j and k. Cryptography and Network Secur ity: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. 12. The ________ cipher structure, which dates back over a quarter century and which, in turn, is based on Shannon’s proposal of 1945, is the structure used by many significant symmetric block ciphers currently in use. 13. The cryptographic strength of a Feistel cipher derives from three aspects of the design: the function F, the key schedule algorithm, and __________ . 
 14. The __________ criterion states that any output bit j of an S -box should change with probability 1/2 when any single input bit i is inverted for all i,j. 
 15. Two alternatives to DES are AES and _________ DES. Cryptography and Network Security: Principles and Practice, 8th Edition , by William Stallings © 2020 Pearson Education, Inc., Hoboken, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. CHAPTER 5: FINITE FIELDS TRUE OR FALSE T F 1. Finite fields play a crucial role in many cryptographic algorithms . T F 2. Rings are a subset of a larger class of algebraic structures called fields.
 T F 3. Groups are defined by a complex set of properties and are difficult to understand. 
 T F 4. Finite fields are a subset of fields, consisting of those f ields with a finite number of elements. 
 T F 5. Cryptographic algorithms do not rely on properties of finite fields. T F 6. A more important class of finite fields, for cryptography, comprises those with 2n elements depicted as fiel ds of the form GF(2n). T F 7. The Advanced Encryption Standard uses infinite fields. 
 T F 8. Groups, rings, and fields are the fundamental elements of a branch of mathematics known as abstract algebra. 
 T F 9. A cyclic group is always commutative and may be finite or infinite. 
 T F 10. A field is a set in which we can do addition, subtraction, multiplication and division without leaving the set. 
 T F 11. It is easy to find the multiplicative inverse of an element in g( p) for large values of p by constructing a multiplication table, however for small values of p this approach is not practical. 
 T F 12. Polynomial arithm etic includes the operations of addition, subtraction and multiplication. 
 T F 13. If we attempt to perform polynomial division over a coefficient set that is not a field, we find that division is not always defined.