Computer Security
Final Test Solutions
Course Introduction
Computer Security explores the principles and practices essential to protecting computer systems and networks from threats, attacks, and unauthorized access. The course covers fundamental concepts including cryptography, authentication, access control, software and network security, and risk management. Students learn to identify vulnerabilities, understand the methods used by attackers, and apply techniques to safeguard information and ensure system integrity, confidentiality, and availability. Through hands-on exercises and case studies, the course prepares participants to implement sound security measures and navigate the evolving landscape of cybersecurity challenges.
Recommended Textbook
Cryptography and Network Security 6th Edition by William Stallings
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20 Chapters
842 Verified Questions
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Page 2
Chapter 1: Overview
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Sample Questions
Q1) A _________ attack attempts to learn or make use of information from the system but does not affect system resources.
Answer: passive
Q2) "The protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity,availability and confidentiality of information system resources" is the definition of _________ .
Answer: computer security
Q3) A loss of __________ is the unauthorized disclosure of information.
A)authenticity
B)confidentiality
C)reliability
D)integrity
Answer: B
Q4) Data origin authentication does not provide protection against the modification of data units.
A)True
B)False
Answer: True
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Page 3
Chapter 2: Classical Encryption Techniques
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Sample Questions
Q1) Symmetric encryption remains by far the most widely used of the two types of encryption.
A)True
B)False
Answer: True
Q2) 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
Answer: Steganography
Q3) 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.
Answer: Caesar
Q4) Cryptographic systems are characterized along three independent dimensions: The type of operations used for transforming plaintext to ciphertext;The way in which the plaintext is processed;and __________ .
Answer: The number of keys used
Q5) The most widely used cipher ever is the __________ .
Answer: Data Encryption Standard (DES)
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Chapter 3: Block Ciphers and the Data Encryption Standard
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Sample Questions
Q1) 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.
A)True
B)False
Answer: False
Q2) Greater complexity in the subkey generation algorithm should lead to greater difficulty of cryptanalysis.
A)True
B)False
Answer: True
Q3) Two alternatives to DES are AES and _________ DES.
Answer: triple
Q4) All other things being equal,smaller block sizes mean greater security.
A)True
B)False
Answer: False
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Page 5
Chapter 4: Basic Concepts in Number Theory and Finite
Fields
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Sample Questions
Q1) A field is a set in which we can do addition,subtraction, multiplication and division without leaving the set.
A)True B)False
Q2) A __________ g of a finite field F or order q is an element whose first q - 1 powers generate all the nonzero elements of F.
15.Consider a field F defined by a polynomial fx).An element b contained in F is called a __________ of the polynomial if fb)= 0.
Q3) The Advanced Encryption Standard uses infinite fields.
A)True B)False
Q4) It is easy to find the multiplicative inverse of an element in gp)for large values of p by constructing a multiplication table,however for small values of p this approach is not practical.
A)True B)False
Q5) The remainder r in the division algorithm is often referred to as a __________ .
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Chapter 5: Advanced Encryption Standard
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Sample Questions
Q1) The S-box is designed to be resistant to known cryptanalytic attacks.
A)True
B)False
Q2) At each horizontal point,State is the same for both encryption and decryption.
A)True
B)False
Q3) The National Institute of Standards and Technology chose the __________ design as the winning candidate for AES.
Q4) The transformations AddRoundKey and InvMixColumn alter the sequence of bytes in State.
A)True
B)False
Q5) The AES key expansion algorithm takes as input a four-word 16-byte)key and produces a linear array of __________ words 176 bytes).
Q6) Virtually all encryption algorithms,both conventional and public- key,involve arithmetic operations on integers.
A)True
B)False
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Chapter 6: Block Cipher Operation
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Sample Questions
Q1) _________ mode is similar to Cipher Feedback,except that the input to the encryption algorithm is the preceding DES output.
A)Cipher Feedback
B)Counter
C)Output Feedback
D)Cipher Block Chaining
Q2) __________ modes of operation have been standardized by NIST for use with symmetric block ciphers such as DES and AES.
A)Three
B)Five
C)Nine
D)Seven
Q3) Five modes of operation have been standardized by NIST for use with symmetric block ciphers such as DES and AES: electronic codebook mode,cipher block chaining mode,cipher feedback mode,__________,and counter mode.
Q4) A __________ cipher can operate in real time and eliminates the need to pad a message to be an integral number of blocks.
Q5) One of the most widely used multiple-encryption scheme is __________ .
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Chapter 7: Random and Pseudorandom Number
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Q1) Three broad categories of cryptographic algorithms are commonly used to create PRNGs: symmetric block ciphers,asymmetric ciphers,and hash functions and message authentication codes.
A)True
B)False
Q2) A __________ is used to produce a pseudorandom string of bits of some fixed length.
A)PRF
B)PRNG
C)OFB PRNG
D)TRNG
Q3) The most important and widely used stream cipher is __________ .
Q4) Operating systems typically provide a built-in mechanism for generating random numbers.For example,__________ uses mouse and keyboard activity,disk I/O operations,and specific interrupts.
Q5) A cryptographically secure pseudorandom bit generator is defined as one that passes the least significant bit test.
A)True
B)False
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Chapter 8: More Number Theory
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Sample Questions
Q1) To determine whether an odd integer n is prime with a reasonable degree of confidence repeatedly invoke TEST n)using randomly chosen values for a.If,at any point,TEST returns _________ then n is determined to be nonprime.
Q2) Discrete logarithms are fundamental to the digital signature algorithm and the _________ algorithm.
Q3) An important requirement in a number of cryptographic algorithms is the ability to choose a large prime number.
A)True
B)False
Q4) A __________ number is an integer that can only be divided by positive and negative values of itself and 1 without having a remainder.
Q5) 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
Q6) Two numbers are __________ if their greatest common divisor is 1.
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Chapter 9: Public-Key Cryptography and Rsa
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Sample Questions
Q1) A __________ is an attack in which the adversary chooses a number of ciphertexts and is then given the corresponding plaintexts,decrypted with the target's private key.
Q2) To counter attacks such as CCAs,RSA Security,Inc. recommends modifying the plaintext using a procedure known as ___________ .
Q3) A __________ is when two sides cooperate to exchange a session key.
Q4) Plaintext is transformed into ciphertext using two keys and a decryption algorithm.
A)True
B)False
Q5) Asymmetric encryption transforms plaintext into __________ using one of two keys and an encryption algorithm.
Q6) Public-key algorithms are based on __________ .
A)permutation
B)mathematical functions
C)substitution
D)symmetry
Q7) The scrambled message produced as output is the __________ .It depends on the plaintext and the key.
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Chapter 10: Other Public-Key Cryptosystems
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Sample Questions
Q1) Since a symmetric block cipher produces an apparently random output it can serve as the basis of a pseudorandom number generator.
A)True
B)False
Q2) A considerably larger key size can be used for ECC compared to RSA.
A)True
B)False
Q3) Elliptic curves are ellipses.
A)True
B)False
Q4) Asymmetric algorithms are typically much slower than symmetric algorithms so they are not used to generate open-ended __________ generator bit streams.
Q5) There is not a computational advantage to using ECC with a shorter key length than a comparably secure TSA.
A)True
B)False
Q6) The purpose of the ___________ algorithm is to enable two users to securely exchange a key that can then be used for subsequent encryption of messages.
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Chapter 11: Cryptographic Hash Functions
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Sample Questions
Q1) The Secure Hash Algorithm was developed by the ___________ .
A)ITIL
B)IEEE
C)ISO
D)NIST
Q2) __________ are measures of the number of potential collisions for a given hash value.
A)MACs
B)Primitives
C)Hash codes
D)Preimages
Q3) Three new versions of SHA with hash value lengths of 256,384,and 512 bits are collectively known as __________ .
A)SHA-3
B)SHA-1
C)SHA-2
D)SHA-0
Q4) Requirements for a cryptographic hash function include ___________ which is the one-way property.
Q5) A message authentication code is also known as a __________ hash function.
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Chapter 12: Message Authentication Codes
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Sample Questions
Q1) A brute-force attack on a MAC is easier than a brute-force attack on a hash function.
A)True
B)False
Q2) The _________ attack is when the attacker is looking for two messages M and M1 that produce the same hash: HM)= HM1)
A)birthday
B)chaining
C)MAC
D)hash
Q3) Insertion of messages into the network from a fraudulent source is a __________ attack.
A)content modification
B)masquerade
C)source repudiation
D)sequence modification
Q4) __________ assures that data received are exactly as sent and that the purposed identity of the sender is valid.
Q5) The HtE approach is used in the __________ protocol to protect WiFi networks.
Q6) NIST SP 800-90,IEEE 802.11i,and TLS/WTLS are three ____________ based on HMAC.
Page 14
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Chapter 13: Digital Signatures
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Sample Questions
Q1) A digital signature can guarantee the integrity but not the source of the message.
A)True
B)False
Q2) The _________ is based on the difficulty of computing discrete logarithms and is based on schemes originally presented by ElGamal and Schnorr.
Q3) It must be relatively difficult to recognize and verify the digital signature.
A)True
B)False
Q4) The DSS approach makes use of a hash function.
A)True
B)False
Q5) In the digital signature algorithm the user's __________ is represented by x,which is a random or pseudorandom integer with 0 < x < q.
A)per message secret number
B)private key
C)global key
D)public key
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Chapter 14: Key Management and Distribution
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Sample Questions
Q1) For symmetric encryption to work the two parties to an exchange must share the same key and that key must be protected from access by others.
A)True
B)False
Q2) Frequent key changes are usually desirable to limit the amount of data compromised if an attacker learns the key.
A)True
B)False
Q3) Each user must share a unique key with the key distribution center for purposes of key distribution.
A)True
B)False
Q4) Several techniques have been proposed for the distribution of public keys.The proposals can be grouped into the following four general schemes: public announcement,publicly available directory,public-key certificates,and ____________.
Q5) A unique identifier for a transaction is a __________ and this identifier may be a timestamp,a counter or a random number,with the minimum requirement being that it differs with each request.
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Page 16
Chapter 15: User Authentication Protocols
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Q1) Presenting an identifier to the security system is the __________ step.
A)authentication
B)verification
C)identification
D)clarification
Q2) The principal underlying standard for federated identity is the __________ which defines the exchange of security information between online business partners.
A)OSAIS
B)SAML
C)RBAC
D)SFIL
Q3) A service to solve the problem of minimizing the number of times that a user has to enter a password and the risk of an eavesdropper capturing the password and using it is known as the __________ .
A)authentication server
B)ticket granting server
C)Kerberos mutual authentication
D)PCBC mode
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Chapter 16: Network Access Control and Cloud Security
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Q1) The _________ is the node that is attempting to access the network and may be any device that is managed by the network access control system.
A)AR
B)RAS
C)IP
D)PS
Q2) _________ is the provision of security applications and services via the cloud either to cloud-based infrastructure and software or from the cloud to the customers' on-premise systems.
A)IaaS
B)PaaS
C)SaaS
D)SecaaS
Q3) The cloud provider in a private cloud infrastructure is responsible for both the infrastructure and the control.
A)True
B)False
Q4) A _________ in an intermediary that provides connectivity and transport of cloud services from CP's to cloud consumers.
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Chapter 17: Transport-Level Security
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Sample Questions
Q1) Unlike traditional publishing environments,the Internet is three- way and vulnerable to attacks on the Web servers.
A)True
B)False
Q2) The World Wide Web is fundamentally a client/server application running over the Internet and TCP/IP intranets.
A)True
B)False
Q3) _________ attacks include impersonating another user,altering messages in transit between client and server and altering information on a Web site.
A)Active
B)Passive
C)Shell
D)Psuedo
Q4) The first element of the CipherSuite parameter is the key exchange method.
A)True
B)False
Q5) __________ provides security services between Transport Layer Protocol and applications that use TCP.
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Chapter 18: Wireless Network Security
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Q1) The IEEE 802.11 protocol stack consists of the logical link control layer,the medium access control layer,and the _________ layer.
Q2) IEEE 802.11 is a standard for wireless LANs.
A)True
B)False
Q3) To certify interoperability for 802.11b products an industry consortium named the __________ was formed.
Q4) The purpose of the discovery phase in the ___________ is for a STA and an AP to recognize each other,agree on a set of security capabilities,and establish an association for future communication using those security capabilities.
A)WPA
B)RSN
C)TKIP
D)WAE
Q5) The actual method of key generation depends on the details of the authentication protocol used.
A)True B)False
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Chapter 19: Electronic Mail Security
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Q1) A _________ is formed by taking the message digest of the content to be signed and then encrypting that with the private key of the signer,which is then encoded using base64 encoding.
Q2) Each PGP entity must maintain a file of its own public/private key pairs as well as a file of private keys of correspondents.
A)True
B)False
Q3) The ________ MIME field is a text description of the object with the body which is useful when the object is not readable as in the case of audio data.
A)Content-Type
B)Content-Description
C)Content-ID
D)Content-Transfer-Encoding
Q4) A specification for cryptographically signing e-mail messages permitting a signing domain to claim responsibility for a message in the mail stream,_________ allow message recipients to verify the signature by querying the signer's domain directly to retrieve the appropriate public key and thereby confirming that the message was attested to by a party in possession of the private key for the signing domain.
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Page 21
Chapter 20: Ip Security
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Q1) The __________ mechanism assures that a received packet was in fact transmitted by the party identified as the source in the packet header and assures that the packet has not been altered in transit.
A)confidentiality
B)authentication
C)security
D)key management
Q2) A __________ attack is one in which an attacker obtains a copy of an authenticated packet and later transmits it to the intended destination.
Q3) The __________ facility is concerned with the secure exchange of keys.
Q4) Transport mode provides protection to the entire IP packet.
A)True
B)False
Q5) __________ provides the capability to secure communications across a LAN,across private and public WANs,and across the Internet.
A)IKE
B)ISA
C)IAB
D)IPsec
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