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Cyber Security Multiple Choice Questions and Answers | Cyber Security MCQs

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Free download in PDF Cyber Security Multiple Choice Questions and Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams like UPSC, NDA, SSC etc. These short solved questions or quizzes are provided by Gkseries./p>

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(1) The Acronym DES stands for
[A] Digital Evaluation System
[B] Digital Encryption Standard
[C] Digital Encryption System
[D] Double Encryption Standard
Answer: Digital Encryption Standard
(2) DES works by using
[A] permutation and substitution on 64 bit blocks of plain text
[B] only permutations on blocks of 128 bits
[C] exclusive ORing key bits with 64 bit blocks
[D] 4 rounds of substitution on 64 bit blocks with 56 bit keys
Answer: permutation and substitution on 64 bit blocks of plain text

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(3) DES

(i) is a symmetric key encryption method

(ii) guarantees absolute security

(iii) is implementable as hardware VLSI chip

(iv) is a public key encryption method

[A] i and ii
[B] ii and iii
[C] i and iii
[D] iii and iv
Answer: i and iii
(4) DES using 56 bit keys
[A] Cannot be broken in reasonable time using presently available computers
[B] Can be broken only if the algorithm is known using even slow computers.
[C] Can be broken with presently available high performance computers.
[D] It is impossible to break ever.
Answer: Can be broken with presently available high performance computers.
(5) Triple DES uses
[A] 168 bit keys on 64-bit blocks of plain text
[B] Working on 64-bit blocks of plain text and 56 bit keys by applying DES algorithm for three rounds.
[C] Works with 144 bit blocks of plain text and applies DES algorithm once.
[D] Uses 128 bit blocks of plain text and 112 bit keys and apply DES algorithm thrice.
Answer: Working on 64-bit blocks of plain text and 56 bit keys by applying DES algorithm for three rounds.
(6) ripple DES
[A] Cannot be broken in reasonable time using presently available computers.
[B] Can be broken only if the algorithm is known using even slow computer.
[C] Can be broken with presently available high performance computers.
[D] It is impossible to break ever.
Answer: Cannot be broken in reasonable time using presently available computers.
(7) Triple DES
[A] is a symmetric key encryption method
[B] guarantees excellent security
[C] is implementable as a hardware VLSI chip
[D] is public key encryption method with three keys.
Answer: guarantees excellent security
(8) Public key encryption method is a system
[A] which uses a set of public keys one for each participant in e-Commerce
[B] in which each person who wants to communicate has two keys; a private key known to him only and a public key which is publicized to enable others to send message to him.
[C] which uses the RSA coding system.
[D] which is a standard for use in e-Commerce.
Answer: in which each person who wants to communicate has two keys; a private key known to him only and a public key which is publicized to enable others to send message to him.
(9) Public key system is useful because
[A] it uses two keys.
[B] there is no key distribution problem as public key can be kept in a commonly accessible database.
[C] private key can be kept secret.
[D] it is a symmetric key system.
Answer: there is no key distribution problem as public key can be kept in a commonly accessible database.
(10) In public key encryption if A wants to send an encrypted message
[A] A encrypts message using his private key
[B] A encrypts message using B’s private key
[C] A encrypts message using B’s public key
[D] A encrypts message using his public key
Answer: A encrypts message using B’s public key
(11) Certification of Digital signature by an independent authority is needed because
[A] it is safe
[B] it gives confidence to a business
[C] the authority checks and assures customers that the public key indeed belongs to the business which claims its ownership
[D] private key claimed by a sender may not be actually his
Answer: the authority checks and assures customers that the public key indeed belongs to the business which claims its ownership
(12) The responsibility of a certification authority for digital signature is to authenticate the
[A] hash function used
[B] private keys of subscribers
[C] public keys of subscribers
[D] key used in DES
Answer: public keys of subscribers
(13) While sending a signed message, a sender
[A] sends message key using public key encryption using DES and hashed message using public key encryption
[B] sends message using public key encryption and hashed message using DES
[C] sends both message and hashed message using DES
[D] sends both message and hashed message using public key encryption
Answer: sends message key using public key encryption using DES and hashed message using public key encryption
(14) Hashed message is signed by a sender using
[A] his public key
[B] his private key
[C] receiver’s public key
[D] receiver’s private key
Answer: his private key
(15) A hashing function for digital signature

(i) must give a hashed message which is shorter than the original message

(ii)must be hardware implementable

(iii) two different messages should not give the same hashed message

(iv) is not essential for implementing digital signature

[A] i and ii
[B] ii and iii
[C] i and iii
[D] iii and iv
Answer: i and iii
(16) A digital signature is required

(i) to tie an electronic message to the sender’s identity

(ii)for non repudiation of communication by a sender

(iii) to prove that a message was sent by the sender in a court of law

(iv) in all e-mail transactions

[A] i and ii
[B] i, ii, iii
[C] i, ii, iii, iv
[D] ii, iii, iv
Answer: i, ii, iii
(17) A digital signature is
[A] a bit string giving identity of a correspondent
[B] a unique identification of a sender
[C] an authentication of an electronic record by tying it uniquely to a key only a sender knows
[D] an encrypted signature of a sender
Answer: an authentication of an electronic record by tying it uniquely to a key only a sender knows
(18) DES and public key algorithm are combined

(i) to speed up encrypted message transmission

(ii) to ensure higher security by using different key for each transmission

(iii) as a combination is always better than individual system

(iv) as it is required in e-Commerce

[A] i and ii
[B] ii and iii
[C] iii and iv
[D] i and iv
Answer: i and ii
(19) Message can be sent more securely using DES by
[A] encrypting plain text by a different randomly selected key for each transmission
[B] encrypting plain text by a different random key for each message transmission and sending the key to the receiver using a public key system
[C] using an algorithm to implement DES instead of using hardware
[D] designing DES with high security and not publicizing algorithm used by it
Answer: encrypting plain text by a different random key for each message transmission and sending the key to the receiver using a public key system
(20) In public key encryption system if A encrypts a message using his private key and sends it to B
[A] if B knows it is from A he can decrypt it using A’s public key
[B] Even if B knows who sent the message it cannot be decrypted
[C] It cannot be decrypted at all as no one knows A’s private key
[D] A should send his public key with the message
Answer: if B knows it is from A he can decrypt it using A’s public key

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