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Computer Science for IGCSE & O level - Data Transmission (Section 13)

1
Which of the following is a critical step in the automatic repeat request (ARQ) process?
Answer
(B)
The receiver sends an acknowledgement to the sender if the data is successfully received.
2
What is the objective of an echo check in data communication?
Answer
(B)
To verify that the data has been received correctly.
3
In the context of packet switching, what does the term 'node' refer to?
Answer
(C)
A router in the network.
4
What is the role of the private key in asymmetric encryption?
Answer
(C)
To decrypt data that has been encrypted with the corresponding public key
5
What does 'ciphertext' refer to in the context of data security?
Answer
(C)
The encrypted form of the message.
6
What is the biggest disadvantage of parity checks?
Answer
(B)
They can only detect some types of errors.
7
In odd parity, if a data byte is 11001100, what is the value of the parity bit?
Answer
(A)
0
8
Which of the following is a purpose of a public key in asymmetric encryption?
Answer
(C)
Shared with anyone who wants to send encrypted messages.
9
Which of the following is an example of symmetric-key cryptography?
Answer
(B)
AES
10
What type of data transmission mode is used in a standard telephone call?
Answer
(C)
Full-duplex
11
What is the main advantage of symmetric encryption?
Answer
(A)
High speed.
12
What is the key benefit of using a digital signature?
Answer
(C)
Non-repudiation and message authenticity
13
Which of the following uses the calculated value which is a sum of values of data, the receiving computer also calculates the value from the block of data and compares the values?
Answer
(C)
Checksum
14
What is 'plaintext' in the context of cryptography?
Answer
(C)
The original, unencrypted data.
15
Which of the following is a characteristic of packet switching?
Answer
A
C
16
Which of the following is an example of a block-level error detection method?
Answer
(D)
All of the above
17
Which of the following is a function of a check digit?
Answer
(B)
To detect errors during transmission.
18
What are the functionalities of ARQ?
Answer
A
B
C
19
Which key is primarily used to verify the sender's identity in the digital signature process using asymmetric encryption?
Answer
(A)
The public key
20
Which mode of transmission is used in a CB radio?
Answer
(B)
Half-duplex
21
In a data transmission system, what is the function of parity checking?
Answer
(B)
To identify errors that may occur during transmission.
22
What is the purpose of a check sum in data transmission?
Answer
(B)
To detect errors in the data during transmission
23
In the ISBN-13 example, what is the function of the check digit?
Answer
(B)
To ensure the ISBN number is valid.
24
What is the role of the sender in automatic repeat request (ARQ)?
Answer
(B)
To retransmit data if an error is detected.
25
What is the primary function of a 'hash' function?
Answer
(B)
To create a unique 'fingerprint' of the data.
26
In encryption, which of the following is the term used to describe the message before it is encrypted?
Answer
(B)
Plaintext
27
Which of the following is the correct name for a form of encryption in which both the sender and the recipient use the same key to encrypt and decrypt?
Answer
(A)
Symmetric key encryption
28
How is the original data sequence restored when using packet switching?
Answer
(B)
Using sequence numbers in the header.
29
Which type of encryption is known for its speed and simplicity?
Answer
(B)
Symmetric encryption
30
What does the term 'node' refer to within the context of packet switching?
Answer
(C)
A router or other intermediary device.
31
What is the main method used by ARQ to ensure reliable data transmission?
Answer
(C)
Retransmission of data.
32
Which error detection method does not rely on the addition of extra bits to the original data?
Answer
(B)
Checksum
33
In a network, what is the role of a 'router'?
Answer
(A)
To connect multiple networks together.
34
What is the primary objective of encrypting data?
Answer
(B)
To make data unreadable to unauthorized users.
35
What are the essential components of a data packet?
Answer
A
B
C
36
What security goal is achieved through encryption?
Answer
(A)
Confidentiality
37
Which is the purpose of the sequence number in the header of a packet?
Answer
(C)
To ensure packets are reassembled in the correct order.
38
What does ARQ stand for in the context of data transmission?
Answer
(C)
Automatic Repeat Request
39
What is the primary purpose of symmetric key encryption?
Answer
(C)
To encrypt data using a single key
40
In data transmission, what is the primary function of a 'checksum'?
Answer
(C)
To check for errors that might occur during transmission.
41
Which method is used to verify the integrity of data during transmission?
Answer
(C)
Checksums
42
For what purpose are check digits used?
Answer
(B)
Error detection during data entry or scanning.
43
In even parity, if a data byte has three 1s, what will the parity bit be?
Answer
(B)
1
44
What is a characteristic of asymmetric encryption?
Answer
(B)
It uses a key pair (public and private).
45
Who should have access to the private key in asymmetric encryption?
Answer
(C)
The receiver of the encrypted message.
46
What is a key characteristic of the term 'ciphertext'?
Answer
(C)
It is unreadable without the correct key.
47
How does a checksum help in data integrity?
Answer
(C)
By verifying that the data hasn't been altered during transmission.
48
What is the core concept behind an echo check?
Answer
(B)
To verify data accuracy.
49
What happens if the sender receives a negative acknowledgement (NAK) in ARQ?
Answer
(B)
The data is retransmitted.
50
In symmetric encryption, what does the term 'key' refer to?
Answer
(A)
A secret code used to encrypt and decrypt the data.