System Analysis and Design

531. Filtering of packets by firewall based on a router has facilities to

  1. prevent access to internet to some clients in the intranet
  2. prevent access at certain specified times
  3. filter packets based on source or destination IP address
  4. prevent access by certain users of the internet to other specified users of the internet
  1. i, iii
  2. i, ii, iii
  3. i, ii, iii, iv
  4. ii, iii, iv
Correct answer: (B)
i, ii, iii

532. By encryption of a text we mean

  1. compressing it
  2. expanding it
  3. scrambling it to preserve its security
  4. hashing it
Correct answer: (C)
scrambling it to preserve its security

533. Encryption can be done

  1. only on textual data
  2. only on ASCII coded data
  3. on any bit string
  4. only on mnemonic data
Correct answer: (C)
on any bit string

534. DES works by using

  1. permutation and substitution on 64 bit blocks of plain text
  2. only permutations on blocks of 128 bits
  3. exclusive ORing key bits with 64 bit blocks
  4. 4 rounds of substitution on 64 bit blocks with 56 bit keys
Correct answer: (A)
permutation and substitution on 64 bit blocks of plain text

535. Triple DES

  1. is a symmetric key encryption method
  2. guarantees excellent security
  3. is implementable as a hardware VLSI chip
  4. is public key encryption method with three keys.
Correct answer: (ii)
guarantees excellent security

536. DES and public key algorithm are combined

  1. to speed up encrypted message transmission
  2. to ensure higher security by using different key for each transmission
  3. as a combination is always better than individual system
  4. as it is required in e-Commerce
  1. i and ii
  2. ii and iii
  3. iii and iv
  4. i and iv
Correct answer: (A)
i and ii

537. Hashed message is signed by a sender using

  1. his public key
  2. his private key
  3. receiver's public key
  4. receiver's private key
Correct answer: (B)
his private key

538. In SET protocol a customer sends a purchase order

  1. encrypted with his public key
  2. in plain text form
  3. encrypted using Bank's public key
  4. using digital Signature system
Correct answer: (D)
using digital Signature system

539. In NetBill's protocol for small payments for internet services

  1. Key to decrypt information is sent to customer by NetBill only when there is enough amount in debit account
  2. The vendor supplies the key to NetBill server when he receives payment
  3. Checksum of encrypted information received by customer is attached to his payment order
  4. Vendor does not encrypt information purchased by customer
  1. i, ii
  2. i, ii, iii
  3. i, ii, iii, iv
  4. i, ii, iv
Correct answer: (B)
i, ii, iii

540. In Electronic cash payment

  1. a customer withdraws “coins” in various denominations signed by the bank
  2. the bank has a database of issued coins
  3. the bank has a database of spent coins
  4. the bank cannot trace a customer
  1. i, ii
  2. i, ii, ii
  3. i, ii, iii, iv
  4. ii, iii, iv
Correct answer: (B)
i, ii, ii
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