Practice Basic Digital Communications Multiple Choice Questions with Answers Quiz-1

Q.1.

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

a) Encryption key
b) Decryption key
c) Encryption & Decryption key
d) None of the mentioned

Explanation

Q.2.

Cipher system can be solved effectively by statistically using

a) Time of occurrence
b) Frequency of occurrence
c) Length of the message
d) None of the mentioned

Explanation

Q.3.

Encryption transformations are known as

a) Diffusion
b) Confusion
c) Diffusion & Confusion
d) None of the mentioned

Explanation

Q.4.

For n input bits the number of substitution patterns are

a) 2n
b) (2n)!
c) 1/2n!
d) 2n!

Explanation

Q.5.

In transposition, the plaintext letters are

a) Substituted
b) Rearranged
c) Removed
d) None of the mentioned

Explanation

Q.6.

The substitution of the letters are done

a) Serially
b) Parallel way
c) Serially & Parallel way
d) None of the mentioned

Explanation

Q.7.

In cipher feedback method, encryption is done on

a) Single individual bits
b) Characters
c) Single individual bits & Characters
d) None of the mentioned

Explanation

Q.8.

In stream encryption, the key sequence repeats itself.

a) True
b) False

Explanation

Q.9.

In which method, key-stream is generated independently?

a) Synchronous
b) Self synchronous
c) Synchronous & Self synchronous
d) None of the mentioned

Explanation

Q.10.

Synchronous ciphers uses

a) Confusion
b) Diffusion
c) Confusion & Diffusion
d) None of the mentioned

Explanation

Q.11.

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

a) True
b) False

Explanation

Q.12.

Public key cryptosystem is also known as

a) One way function
b) Two way function
c) Feedback function
d) None of the mentioned

Explanation

Q.13.

Euler’s totient function is determined by

a) pq
b) (p-1)(q-1)
c) (p+1)(q+1)
d) p/q

Explanation

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