Download cpopcs772FinalFall16

CS 772/872
Network and Systems Security
Fall 2016
2nd Exam
Time 2 & 1/2 hours
Open Book & Notes
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CATALIN POP
CPOP
Each question is 10 points.
1. 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 after the first round and just before the
permutation step.
Since the answer is all 0s when XOR we then use S-BOX substitution S5.
0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010
0010 0010
EFA7 2C4D
2. 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 the first round.
X1 = 0000 0000 0000 0000
X2 = 0000 0000 0000 0000
X3 = 0000 0000 0000 0000
X4 =0000 0000 0000 0000
K1 = 0000 0000 0000 0000
K2 = 0000 0000 0000 0000
K3 = 0000 0000 0000 0000
K4 = 0000 0000 0000 0000
New values:
X1 = MULT X1 with K1 = 0000 0000 0000 0000
X3 = add X2 with k2 = 0000 0000 0000 0000
X2 = add X3 with K3 = 0000 0000 0000 0000
X4 = MULT X4 with K4 = 0000 0000 0000 0000
All 0s
3. Assume AES is used to encrypt 128-bit data where all its octets are 52 in HEX
using 128-bit key of all 0s. Show the result at the end of the first round.
Hex = 52
S-box = 00
Key = 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0000 0000 0000
1st round = 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0000 0000 0000 0000
4. Which of the block chaining methods allows the pad to be generated in advance
of the message arrival?
OFB
5. Given a public key <3,6>.
List all possible values of d for the private key <d,6>?
1,3,5
6. Calculate 𝟑𝟔𝟓 using the binary representation of 65. Do NOT use calculator.
3
7. Consider Diffie-Hellman with p=7 and g=5.
Assume Alice picks 2 and Bob picks 3 as their random numbers.
What is the value of the shared secret between Alice & Bob Following
Diffie-Hellman message exchange?
TA = 2
TB = 6
X = 6^2 mod 7 = 1
Y = 2^3 mod 7 = 1
8. If you randomly select a number p < 100,
what is the probability that p is a prime number?
25% chance since there are 25 prime numbers out of 100
9. In Zero Knowledge Proof system using Graph Isomorphism.
Assume Alice has the following two graphs as her public key.
What is her private key?
f -> A
g -> B
h -> C
I -> D
J -> E
In assignment #5 explain why cs772 needs to access the signed certificates:
cs772, Y & C.
When CS 772 does the verify command we verify the signatures using the
senders_cert.pem
openssl smime -decrypt -out $2.sig -des3 -in $2 -recip $1_cert.pem -inkey
$1_privatekey.pem
openssl smime -CAfile ca_cert.pem -verify -in $2.sig -out $2.txt -signer
sender_cert.pem <- right there