CN Grand Test 1 Question 27

Question

Answer 1

in symmetric key cryptography both encryption and decryption is done using shared transmission key.

Raju encrypts message using shared transmission key i.e)ka(m).

and transmit the shared key on transmission medium.

any intruder receives Raju's shared key and send message using his(trudy) key i.e)kt(m)

but Rani doesn't know this message is guarantly delivered by Raju.

the encrypted message can be readable by intruder trudy.in symetric key cryptography man in middle attacks occur

Comments

So option A right....authentication is not ensuered...right?

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Firstly there is a confusion between Raja Rani and Alice. I assume by Alice they mean Rani. Here key  is known by only these two. (nobody else knows).

So, Rani knows both (a) and (b)

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here alice is an intruder.

so he can encrypt message that is forwarded by the Raju,and send to Rani and proves message is sent by Raju only.but Rani doesn't know the message is comes from Alice