CS 772/872
Network and Systems Security
Fall 2014
Midterm Exam
Time 2 & 1/2 hours
Open Book & Notes
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All Questions are of equal weight.
Show your output in HEX not in binary.
1. The following cipher message was produced using the Rail Fence with 3 rails:
'noviofl ignarkri'
What is the corresponding plain text?
2. Assume DES is used to encrypt 64-bit data of all 0s using 64-bit key of all 0s.
Show the output of the S-Boxes of the first round and just before the
permutation step.
3. Assume IDEA is used to encrypt 64-bit data of all 0s using 128-bit key of all
0s. Show the result at the end of all the 17 rounds.
4. Assume AES is used to encrypt 128-bit data where all its octets are 52 in HEX
using 128-bit key of all 1s. Show the result at the end of the first round.
5. All chaining methods uses an IV block. Describe the effect of altering
(accidentally or intentionally) the IV block on the subsequent received cipher
blocks. Describe the effect on all the chaining methods presented in class.
6. Assume Alice and Bob share a common secret E.
Describe how Alice can authenticate herself to Bob by sending him one
message using Symmetric Encryption.
7. Assume Alice and Bob share a common secret E.
Describe how Alice can authenticate herself to Bob by sending him one
message using Message Digest.
8. Assume Alice has pair of public/private keys and her public key is known to
Bob. Describe how Alice can authenticate herself to Bob by sending him one
message using Asymmetric Encryption.
9. Given a public key <3,6>.
List all possible values of d for the private key <d,6>?
10.Calculate 𝟑𝟔𝟓 using the binary representation of 65. Do NOT use calculator.
11.Consider Diffie-Hellman with p=7 and g=3. Assume Alice picks 2 as her
random number while Bob picks 3 as his random number. What is the value of
the shared secret between Alice & Bob following Diffie-hellman message
exchange?
12.Consider the Zero Knowledge Proof Systems using Graph Isomorphism.
Assume Alice used the following two graphs as her public key.
What is her private key?