50 Computer Networks MCQs with Answers

Question 31

Using public key cryptography, X adds a digital signature σ to a message M, encrypts (M,σ) and sends it to Y, where it is decrypted. Which one of the following sequence of keys is used for operations?

• Encryption : X’s private key followed by Y’s private key. Decryption : X’s public key followed by Y’s public key.
• Encryption : X’s private key followed by Y’s public key; Decryption : X’s public key followed by Y’s private key
• Encryption : X’s private key followed by Y’s public key; Decryption : Y’s private key followed by X’s public key.
• Encryption : X’s public key followed by Y’s private key; Decryption : Y’s public key followed by X’s private key.

Question 32

Anarkali digitally signs a message and sends it to Salim. Verification of the signature by Salim requires

• Anarkali’s public key.
• Salim’s public key.
• Salim’s private key.
• Anarkali’s private key.

Question 33

Suppose that everyone in a group of N people wants to communicate secretly with the N–1 others using symmetric key cryptographic system. The communication between any two persons should not be decodable by the others in the group. The number of keys required in the system as a whole to satisfy the confidentiality requirement is

• 2N
• N(N – 1)
• N(N – 1)/2
• (N – 1)²

Question 34

How many bytes of data can be sent in 15 seconds over a serial link with baud rate of 9600 in asynchronous mode with odd parity and two stop bits in the frame?

• 10,000 bytes
• 12,000 bytes
• 15,000 bytes
• 27,000 bytes

Question 35

A firewall is to be configured to allow hosts in a private network to freely open TCP connections and send packets on open connections. However, it will only allow external hosts to send packets on existing open TCP connections or connections that are being opened (by internal hosts) but not allow them to open TCP connections to hosts in the private network. To achieve this the minimum capability of the firewall should be that of

• A combinational circuit
• A finite automaton
• A pushdown automaton with one stack
• A pushdown automaton with two stacks

Question 36

An email contains a textual birthday greeting, a picture of a cake and a song. The order is not important. What is the content-type?

• Multipart/mixed
• Multipart/parallel
• Multipart/digest
• Multipart/alternative

Question 37

Phase transition for each bit are used in

• Amplitude modulation
• Carrier modulation
• Manchester encoding
• NRZ encoding

Question 38

In networking, UTP stands for

• Unshielded T-connector port
• Unshielded twisted pair
• Unshielded terminating pair
• Unshielded transmission process

Question 39

Data is transmitted continuously at 2.048 Mbps rate for 10 hours and received 512 bits errors. What is the bit error rate?

• 6.9 e-9

• 6.9 e-6

• 69 e-9

• 4 e-9

Question 40

The IEEE standard for WiMax technology is

• IEEE 802.16
• IEEE 802.36
• IEEE 812.16
• IEEE 806.16