41. Which one of the following is true for asymmetric-key cryptography?
a. Private key is kept by the receiver and public key is announced to the public
b. Public key is kept by the receiver and private key is announced to the public
c. Both private key and public key are kept by the receiver
d. Both private key and public key are announced to the public
Answer: (a).Private key is kept by the receiver and public key is announced to the public

42. A Trojan horse is
a. A program that performs a legitimate function that is known to an operating system or its user and also has a hidden component that can be used for nefarious purposes like attacks on message security or impersonation
b. A piece of code that can attach itself to other programs in the system and spread to other systems when programs are copied or transferred
c. A program that spreads to other computer systems by exploiting security holes like weaknesses in facilities for creation of remote processes
d. All of the above
Answer: (d).All of the above

43. In substitution, a character in the plaintext is always changed to the same character in the ciphertext, regardless of its position in the text
a. polyalphabetic
b. mono alphabetic
c. transpositional
d. multialphabetic
Answer: (b).mono alphabetic

44. Using data p=3, q=11, n=pq, d=7 in RSA algorithm find the cipher text of  the given plain text SUZANNE
Answer: (a).BUTAEEZ

45. Which of the following protocols is an application layer protocol that establishes, manages and terminates multimedia sessions?
a. Session Maintenance Protocol
b. Real - time Streaming Protocol
c. Real - time Transport Control Protocol
d. Session Initiation Protocol
Answer: (d).Session Initiation Protocol

46. Match the following port numbers with their uses :

(a) 23 (i) World wide web
(b) 25 (ii) Remote Login
(c) 80 (iii) USENET news
(d) 119 (iv) Email

code (a)  (b)  (c)  (d)
a. (iv)   (i)  (ii)  (iii)
b. (ii)   (i)  (iv)  (iii)
c. (ii)   (iv)  (iii)   (i)
d. (ii)  (iv)   (i)     (iii)
Answer: (d).(ii)  (iv)   (i)     (iii)

47. Which of the following is not associated with the session layer ?
a. Dialog control
b. Token management
c. Semantics of the information transmitted
d. Synchronization
Answer: (c).Semantics of the information transmitted

48. What is the size of the 'total length' field in IPv4 datagram ?
a. 4 bits
b. 8 bits
c. 16 bits
d. 32 bits
Answer: (c).16 bits

49. Which of the following is/are restriction(s) in classless addressing ?
a. The number of addresses needs to be a power of 2
b. The mask needs to be included in the address to define the block
c. The starting address must be divisible by the number of addresses in the block
d. All of the above
Answer: (d).All of the above

50. The process of dividing an analog signal into a string of discrete outputs, each of constant amplitude, is called :
a. Strobing
b. Amplification
c. Conditioning
d. Quantization
Answer: (d).Quantization

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