bitcoinscryptonews.com – MCQs, Mock Tests | Electrical measurements Digital Communications MCQs set-14

In digital communication, interaction between ______ is possible.

1. Any layer to layer
2. One layer to next layer
3. layers
4. None of the mentioned

✅ Correct Answer: 2

Some advantages of spread spectrum are

1. Low susceptibility
2. Immunity to jamming
3. Reduced interference
4. All of the mentioned

✅ Correct Answer: 4

Processing gain is the ratio of message bandwidth to signal bandwidth.

1. True
2. False
3.
4.

✅ Correct Answer: 2

Which is better for avoiding jamming?

1. Direct sequence spread spectrum
2. Frequency hopping spread spectrum
3. Time hopping spread spectrum
4. None of the mentioned

✅ Correct Answer: 2

Which is more bandwidth efficient?

1. Direct sequence spread spectrum
2. Frequency hopping spread spectrum
3. Time hopping spread spectrum
4. None of the mentioned

✅ Correct Answer: 3

Which is more simpler to implement?

1. Direct sequence spread spectrum
2. Frequency hopping spread spectrum
3. Time hopping spread spectrum
4. None of the mentioned

✅ Correct Answer: 1

Which uses orthogonal codes?

1. Synchronous CDMA
2. Asynchronous CDMA
3. Synchronous & Asynchronous CDMA
4. None of the mentioned

✅ Correct Answer: 1

Which is more suitable when large number of transmitters are used?

1. Synchronous CDMA
2. Asynchronous CDMA
3. Synchronous & Asynchronous CDMA
4. None of the mentioned

✅ Correct Answer: 2

CDMA rejects

1. Narrow band interference
2. Wide band interference
3. Narrow & Wide band interference
4. None of the mentioned

✅ Correct Answer: 1

Frequency planning is very essential in

1. FDMA
2. TDMA
3. FDMA & TDMA
4. None of the mentioned

✅ Correct Answer: 3

CDMA uses

1. Hard hand off
2. Soft hand off
3. Hard & Soft hand off
4. None of the mentioned

✅ Correct Answer: 2

In public key cryptosystem _____ keys are used for encryption and decryption.

1. Same
2. Different
3. Encryption Keys
4. None of the mentioned

✅ Correct Answer: 2

In public key cryptosystem which is kept as public?

1. Encryption keys
2. Decryption keys
3. Encryption & Decryption keys
4. None of the mentioned

✅ Correct Answer: 1

In a trapdoor function, the functions are easy to go in

1. One direction
2. Two directions
3. All directions
4. None of the mentioned

✅ Correct Answer: 1

Pretty good privacy program is used for

1. Electronic mails
2. File encryption
3. Electronic mails & File encryption
4. None of the mentioned

✅ Correct Answer: 3

PGP system uses

1. Private key system
2. Public key system
3. Private & Public key system
4. None of the mentioned

✅ Correct Answer: 3

Private key algorithm is used for _____ encryption and public key algorithm is used for _____ encryption.

1. Messages, session key
2. Session key, messages
3. Can be used for both
4. None of the mentioned

✅ Correct Answer: 1

Which are called the block ciphers?

1. IDEA
2. CAST
3. Triple-DES
4. All of the mentioned

✅ Correct Answer: 4

Which has a key length of 128 bits?

1. IDEA
2. Triple-DES
3. IDEA & Triple-DES
4. None of the mentioned

✅ Correct Answer: 1

Which algorithm can be used to sign a message?

1. Public key algorithm
2. Private key algorithm
3. Public & Private key algorithm
4. None of the mentioned

✅ Correct Answer: 1

Examples of hash functions are

1. MD5
2. SHA-1
3. MD5 & SHA-1
4. None of the mentioned

✅ Correct Answer: 3

A cryptographic hash function has variable output length.

1. True
2. False
3.
4.

✅ Correct Answer: 2

A set of numbers is called as super increasing if

1. Each element is greater than previous element
2. Each element greater than sum of all the previous elements
3. Each element greater than the average of all elements
4. Each element lesser than the sum of all the elements

✅ Correct Answer: 2

Knapsack problem can be solved by

1. Public key cryptosystem
2. Private key cryptosystem
3. Public & Private key cryptosystem
4. None of the mentioned

✅ Correct Answer: 1

Merkle hellman is a symmetric cryptosystem.

1. True
2. False
3.
4.

✅ Correct Answer: 2

In this Merkle Hellman method same key is used for encryption and decryption.

1. True
2. False
3.
4.

✅ Correct Answer: 2

Cipher system can be solved effectively by statistically using

1. Time of occurrence
2. Frequency of occurrence
3. Length of the message
4. None of the mentioned

✅ Correct Answer: 2

Encryption transformations are known as

1. Diffusion
2. Confusion
3. Diffusion & Confusion
4. None of the mentioned

✅ Correct Answer: 3

For n input bits the number of substitution patterns are

1. 2n
2. (2n)!
3. 1/2n!
4. 2n!

✅ Correct Answer: 2

In transposition, the plaintext letters are

1. Substituted
2. Rearranged
3. Removed
4. None of the mentioned

✅ Correct Answer: 2

The substitution of the letters are done

1. Serially
2. Parallel way
3. Serially & Parallel way
4. None of the mentioned

✅ Correct Answer: 2

In cipher feedback method, encryption is done on

1. Single individual bits
2. Characters
3. Single individual bits & Characters
4. None of the mentioned

✅ Correct Answer: 1

In stream encryption, the key sequence repeats itself.

1. True
2. False
3.
4.

✅ Correct Answer: 2

In which method, key-stream is generated independently?

1. Synchronous
2. Self synchronous
3. Synchronous & Self synchronous
4. None of the mentioned

✅ Correct Answer: 1

Synchronous ciphers uses

1. Confusion
2. Diffusion
3. Confusion & Diffusion
4. None of the mentioned

✅ Correct Answer: 1

Public key cryptosystem uses same key for both encryption and decryption.

1. True
2. False
3.
4.

✅ Correct Answer: 2

Which should be kept as a secret in public key cryptosystem?

1. Encryption key
2. Decryption key
3. Encryption & Decryption key
4. None of the mentioned

✅ Correct Answer: 2

Public key cryptosystem is also known as

1. One way function
2. Two way function
3. Feedback function
4. None of the mentioned

✅ Correct Answer: 1

Eulerâ€™s totient function is determined by

1. pq
2. (p-1)(q-1)
3. (p+1)(q+1)
4. p/q

✅ Correct Answer: 2

Pretty good privacy (PGP) security system uses

1. Public key cryptosystem
2. Private key cryptosystem
3. Public & Private key cryptosystem
4. None of the mentioned

✅ Correct Answer: 3

Public key cryptosystem is used for the encryption of

1. Messages
2. Session key
3. Session key & Messages
4. None of the mentioned

✅ Correct Answer: 2

For digital signatures private key cryptosystem is used.

1. True
2. False
3.
4.

✅ Correct Answer: 2

Data compression includes

1. Removal of redundant character
2. Uniform distribution of characters
3. Removal of redundant character & Uniform distribution of characters
4. None of the mentioned

✅ Correct Answer: 3

PGP offers _____ block ciphers for message encryption.

1. Triple-DES
2. CAST
3. IDEA
4. All of the mentioned

✅ Correct Answer: 4

Which block cipher has key length of 128 bits?

1. IDEA
2. CAST
3. IDEA & CAST
4. None of the mentioned

✅ Correct Answer: 3

These three ciphers can operate of ______ of plaintext and cipher text.

1. 128 bit blocks
2. 64 bit blocks
3. 256 bit blocks
4. 156 bit blocks

✅ Correct Answer: 2

The key size of DES is

1. 56 bits
2. 64 bits
3. 128 bits
4. 168 bits

✅ Correct Answer: 1

Which operation is used in encryption using IDEA?

1. Addition modulo 216
2. Bit wise XOR
3. Addition modulo 216 & Bit wise XOR
4. None of the mentioned

✅ Correct Answer: 3

What is the key size allowed in PGP?

1. 1024-1056
2. 1024-4056
3. 1024-4096
4. 1024-2048

✅ Correct Answer: 3

Which algorithm is used for public key encryption?

1. RSA
2. Diffie-Hellman
3. RSA & Diffie-Hellman
4. None of the mentioned

✅ Correct Answer: 3

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