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0% found this document useful (0 votes)
124 views12 pagesMid
Uploaded by
khalidCopyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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/ 12
En cas [ea
Student Name (in English): Student ID:
Question 3: Calculation question To be answered in (30) Minutes [4-] /_8_ Marks
m using RSA, Trudy intercepts the cipher text C=10 sent to Alice
A. Ina public key system v
whose public key is@=11, n-51. What is the plain text M?_(3Marks)
a’ ps3 alee
Ww prq- Bl a
a Bn) = O-P)(\-4)
ee eb 2 32
a exdz\ wed Gt)
3)
Md: \ wed 32
. “a
od 3\ 5\ Gagne
B. Consider a Diffie-Hellman scheme with a common prime p = 71 and -
csi generator g=7
sy 1. I Alice has private key a= 5, what is Alice’s public key?
2. If Bob has private key b= 3, what is his
Seed ky = of” wed BF
od a
mod T _ A A Ce
Sedat Name (in English) Studene ID:
{6 fresources is shared at different levels, we could be used to “signal” information across 4
communication path not intended as such by systern’s designers called ~
1S Covert channe!
'. Compartnent
© MIS
Biba Modet
Questions TF ‘To be answered in (10) Minutes [ 3 J/-5. Mate
2 | Cayabilics fs good when uses manage their own ies, and easy to
change Fights © a resource,
| Compartment entorees assess contol up and down but Malilevel
Security (MLS) enforces restrictions across security level
cH
ler
co
“@ | One advantage of application Proxy is to filter bad data application
Seatecree wane e
x4
=
e}
~] Gaieresognion Tran sample of someing you are
‘ oresecces contol matrirby ecu
7 | Anarchy model asa PRT irustmods offs maltiple wasted CAS, BYOWieh
‘nay have 80 or more ctificates, jst to verify cerificates, User ean
‘dside which CAsto tat
[3] Pablo Rey Tafastoctue PRI couais
(CRLs) which neoled te seciely we
9" | Based on Hamming dstunce, a (1OTTN
[10 | Compare one-to-many in Biometrics adent Name (in English): Student ID:
ant To be answered in (30) Minutes [21 /\s. Masks
Choose the correct answer and fill the box below with your final choice:
1A eraya
ae UK ee
1. One of the main reasons that “something you know” more popular than “something you
have” and “something you are” is
a, Expensive
b. Can be detected
Ve Nocost (Pvc)
d. Difficult to remember
2. At which layer of the Internet protocol stack does stateful packet filter firewall operate?
a. Network layer
b. Application layer
¢. Physical layer
VE Transport layer
3. could be used as a mitigation technique against flooding of the server by bots
masking as new customers.
a. C-List
b. MLS
ve CAPTCHA
d. BLP
4, Network-based Intrusion Detection System (NIDS) could use
a” Only signature based approach
b. Only anomaly based approach
¢. Signature and/or anomaly based approaches
wk None of the above
~~ for detecting intrusions.
5. Finger print to authenticate should pass two phases , below figure showing. phase.
oa &
Ss wi
———
Ve Recognition
b. Enrollment
c. Identification
d. None of the above NA? CON ee)
Student ID:
dent Name (in English):
Gk :
C. Suppose that Bob's public key consists of (27, 45, 10, 29) along with the multiplier m=
6 and modulus n= 53. (3Marks)
4) Enerypt the message M= 1100010 using the public key. Give your result in decimal
Gk (22,45 ,10,24)
My = ZTH4S (22)
mae 23
Mz 200),
'p) Find mand the private key.
whet cl med av
Sk = GK Jan ane
wtb = \ mod 53
Bf we
era | ond oS Sess
eso eal 53.7 rae
63/424 enn Ben ss 45 ag
Be oceckuas, :
ee
aa at
a ee
136 ©) Find the plaintext given the cipher text C = 37. Give your answer in binary.
S3%7~20-
935/4216 a
‘ wrod
D. Use the repeated squaring method to efficient
yi
for 123 ,Xeu aap ss
‘A- Implement the ‘A5/\ algorithm. Suppose that, after a particular step, the values in
the registers are
X = (a0, 01,--->%18) = (101010109010101010%)
Y =(yo.w,-+-.y21) = (110011001100110011001%)
Z = (zo. 21, +++ 222) = (11100001119000011110000)
‘The key stream algorithm is
A5/1: Keystream
+Ateach step: m= maj(xs Yio Zio)
+ Examples: maj(0,1,0)= 0 and maj(1,1,0)= 1
+f x,= mthen Xsteps
+ f= H Ox OA Org
+ xj= pa for 1= 18,17,..-91 8d %=
«If yyo= mthen Ysteps
+ t= oF
+ yp= Yea for 7= 21,20,...,1 and Yo “t
«lf z= mthen Zsteps
Zy@zq92 221 PF22
Fea for i= 22,21,..-,1 and 2) = 6
-Keystream bit is x;®y21972
“List the next 2 Keystream bits and give the contents of X, Y, and Z after these 2 bits have
‘been generated.
eye
wm = mo} (10,1) = 1
%={o\ MARS ASooee tS WN Sta \ G0 e160 «0
ae
ZATZ\ WV PO OOO OSS WAV Doo S Ls 6 @0 G0 eo
: =O
4
bee Aes Fa as
m= may (0,81) =o ‘
5 \
=) 010100 \0\0 V0 Jo \o\ SE =O el @oe\=9
4s as ©o WW Oo WV oo ool\at=o @\ eh
Page S0f7
TCCIS| Vice Deanery of Development and Quality
514 7. Using shift cipher to encrypt: “sunny day” , key = 5; the cipher text will be
VXQQB GDB. Bera kiN Uooac ere
a. True ¢
Ws. False Diss Eee
Reason: os
XZ5S 0 LFO
atl Bhith bys the Massage
Soe erate Sees eee
8. The key for the following cipher “ZMXNMD BZM TRD BHOGDQ” which is
known to have been encrypted with a shift cipher is K=25:-
ae True at
b. False
Reason:
ake de tau atin. Tay deus,
9. The key for the following cipher K~ GOLEGABDFAUKMNEORSTUVWXYZ,
‘te enerypion forthe paints” Universi” gives MDPZMBHOGD
a, True
er False cow
Reason:
- Ty
cs UMEVGRSETY
10, Alice and Bob are using the one-time pad cryptosystem. Suppose that the plaintext
is 1011 0101 110 and the ciphertext is 0001 0110 111. The Key will be:
va 1010 0011 001 s00\;00 AN
b. 1010 1100101 Jo\s es) ie
oe a4 Vere Wl soi
Pecek as —
. eT ane:
ion 2: Fill in the blank To be answered in ( 10 ) Minutes [2:5] /_3_ Mark:
A- Classify each of the following as a violation of
{ RED ee eee Clee D E |
| Confidentiality | Integrity CBC Availability | Authentication |
1. Alice changes the amount on Bob's check from 100 to 1000 Taheqesby —~
2. Alice uses Bob’s password to access his account Audlaaricalion—
3. Alice couldn’t access her Bank account to transfer money at 10:pm aasallabshly
4, Alice copies Bob's homework mgd CC a
B- Consider the following figure and Answer the following:
‘sender sends ane eat computes the Mae
with the messape
1, How does this system work with MAC to ensure data integrity?
When re seader wauh be preven) aunoulherized wei
a
oF information, So will Sead MAC wilh message bo
ee redver, aud veciver wit Compaire iF re Mac Wok vecived
is Same MAc rab rave , iF iW’s qsame = ensure dala
2. Does the message received correctly? Yes or No? Explain the reason? ‘abegeibe,
" yes ; because Whe reciver resived tae
Same MAc nal Seader Send ib. ‘To beansweredin (i) Minutes [/ ]/_4. Mae
a SS
TAM bea confidential email that Alice wants to send to Bob, Explain why or why not the
ing sending options can be the best choice for protecting the confidentiality of Alice's
At? (Note:{ ) means encrypting with public key and] means enerypting with private key)
2)Send (Mle
Tositne choice Ww wah Wwe hed Onsices becouse wat Secure
bySend [(MIne ie
\pedd chitee, Alike Seud email wil Le sign
cpm Vpseae erept bob
ered encrypted by alice
BN peer
yard ne one caw
g)Send (M1 ie) ae
impossible Omeice »
Send (UM ee Yao a
apenibie eeiee y Woe Ewail evcrypled by
Cot ope ema a
oat aren neswork at aml is dite nto tree indspendet component, called
Sn WLAN icatesthose nods which ar fr he eof dens. VLAN2 cons nodes
Voy faulty and ther univesity taf VLAN3 cotains university servers such as web-
siarer and thers The tree VALNs ae dilly connected t» gateway outer as
ehee, Se eb eS ee
a
14: Open question To be answered in (20) Minutes [ 5 ]/_s.Ma
Oo ———————
A. Suppose you are a merchant and you decide to use a biometric fingerprint device to
authenticate people who make credit card purchases at your store. You can choose
between two different systems:
System A has a fraud rate of 1% and an insult rate of 5%, while
System B has a fraud rate of 5% and an insult rate of 1%.
1. Which system is more secure and why?
é Ne 2 Sh
Sysewn N vermare secure because ne Se ete
2. Which system is more user-friendly and why?
sustem Bo yrove user Pricudly » error cate 217,
Be Nate a people oe ed he use Primgerpront repealed ly
B. The high water mark principle and low water mark principle both apply in the realm of
multilevel security (MLS).
© 1 Briefly explain the high water mark principle andthe low water mark principle in the context
y of MLS.
Ligh water mak work with conPidinliality .ib's mean your
level stack out with marimum low ley Wok you wauk Yo wed
Now water mpek= evock ehh wheqcily 5 iS mean your achive
\a/e\ ond Clan aemnetetEEN Scal
2. Is BellLaPadula (BLP) security model consistent with a high water mark principle, a low
water mark principle, both, or neither? 2
Ye BLP wilh Wah waler marckOrinaple
--a om
C:
A Unix password file often contains a use
The file is often readable by all users (that is
value improve security (including what
Salih 45 wow Secced Value add
Yo woke dichonany alback
Use pre Computed value oe OO]
Choose the correct answer (s) and state the reason for ‘Your choice,
1. Inthe Advanced Encryption Standard (AES) cipher, “shift rows” is a step that contributes
\ Confusion 4
b. Diffusion
Bema occa pela on Ship behuseen Cipher auol plain |
kK
2. One source of. confusion within a DES round is --
Ve S- boxes
‘b. P-boxes
Reason:
te
3. TEA isan example of. ciphers,
Oreos] canto Key”
4. Each step of
a. DES
VE RCE
Reason;
ci
SA.
a. AES
veo 3DES
Reason: a
te he wine Secure ron DES.
6. Data Encryption Standard (DES) used in Electronic Code Book (ECB) mode
Ee makes it unsuitable for long messages.
4 ac True
produces a keystream byte.
's a symmetric algorithm that use 112 bit keylength — SeFluave
Se Mak is wore speed
> produce okey
ream iu byte.
ty | CCIS | Vice Deanery of Development and Quality
20140514 ion 5:
To be answered in (15) Minutes [ |: ]/_2. Marks
DEN is a Feistel block cipher based on the use of two addition operations and two
substitution boxes (S-Boxs). The structure of DEN is given as follows:
Substitutic
\N\.000. \N.0
R
yo 10
Be—— K .0000
2.2,0.0.00.0\.0.0,
o
Bees 4. Bea cs cae
The S-Box of DEN is given as follows: (first 2 bits represent the row and the last 3 bits
represent the column)
[oro [oi [100 [ior [iso Jatt
00 ie wt il 10 jor 00, 10
OL i Ol o1 10 10 00 iL u
[40 00 10 i 00 i o1 it i
iL 10 ol in 00 a
ed on the above information, encrypt the following 20-bits message (P), given the
nintext = 1100010111}1110001110
y= 1110001010
rt B- The following ciphertext message was encrypted with a one-time pad is KITLKE.
Using this table:
\ e=000 h=001 1-010 k=011 I=100 r=101 s=110 t=111 |
1- Ifthe key is "LEKEKR" what is the plaintext?
eWW clo WV loo el\ ooo