NetworkSecurity
Question 1 
The value of 3^{51} mod 5 is ______.
3  
5  
2  
1 
⇒ 3^{1} = 3 ⇒ 3 mod 5 = 3
3^{2} ⇒ 9 mod 5 = 4
3^{3} ⇒ 27 mod 5 = 2
3^{4} ⇒ 81 mod 5 = 1
3^{5} ⇒ 243 mod 5 = 3
For every four numbers sequence is repeating.
So, (51 % 4) = 3
⇒ 3^{3} = 27
⇒ 27 mod 5 = 2
Question 2 
In an RSA cryptosystem, the value of the public modulus parameter n is 3007. If it is also known that Φ(n) = 2880, where Φ() denotes Euler's Quotient Function, then the prime factor of n which is greater than 50 is ______.
107  
97  
45  
92 
n = 3007, fi(n) = 2880 → fi(n) = (p – 1) (q – 1),
where p, q are prime factor of n.
The unit place of n is 7, it is a prime number and factor will be
1.7=7
11*17
21*37
31*47
….
31*97 =>3007
n = 3007 => 31*97
Therefore, 31 & 97 are the two prime numbers, which is satisfying the condition and 97 is greater than 50.
So, 97 is the correct answer.
Other methods:
When ϕ(n) is given when n=pq where p and q are prime numbers, then we have
ϕ(n) = (p−1)(q−1) = pq−(p+q)+1
But pq=n,
therefore, ϕ(n) = n−(p+q)+1 and p+q = n+1−ϕ(n).
Now, p and q are the roots of the equation,
x^{2} − (p+q)x + pq = (xp)(xq)
Substituting for p+q and pq in the above equation
x^{2}  (n+1ϕ(n))x + n
Question 3 
Using public key cryptography, X adds a digital signature to message M, encrypts <M, σ>, and sends it to Y, where it is decrypted. Which one of the following sequences of keys is used for the operations?
Encryption: X’s private key followed by Y’s private key; Decryption: X’s public key followed by Y’s public key  
Encryption: X’s private key followed by Y’s public key; Decryption: X’s public key followed by Y’s private key  
Encryption: X’s public key followed by Y’s private key; Decryption: Y’s public key followed by X’s private key  
Encryption: X’s private key followed by Y’s public key; Decryption: Y’s private key followed by X’s public key 
Encryption: Source has to encrypt with its private key for forming Digital signature for Authentication. Source has to encrypt the (M, σ) with Y’s public key to send it confidentially.
Decryption: Destination Y has to decrypt first with its private key, then decrypt using source public key.
Question 4 
A layer4 firewall (a device that can look at all protocol headers up to the transport layer) CANNOT
block entire HTTP traffic during 9:00PM and 5:00AM  
block all ICMP traffic  
stop incoming traffic from a specific IP address but allow outgoing traffic to the same IP address  
block TCP traffic from a specific user on a multiuser system during 9:00PM and 5:00AM 
(B) Possible because it is network layer protocol.
(C) Possible because SP address is present in Network layer.
(D) Not possible, because to block specific user, we need user id which is present in Application layer.
Question 5 
In the RSA public key cryptosystem, the private and public keys are (e, n) and (d, n) respectively, where n = p*q and p and q are large primes. Besides, n is public and p and q are private. Let M be an integer such that 0 < M < n and f(n) = (p 1)(q1). Now consider the following equations.
I. M’= M^{e} mod n M = (M’)^{d} mod n II. ed ≡ 1 mod n III. ed ≡ 1 mod f(n) IV. M’= M^{e} mod f(n) M = (M’)^{d} mod f(n)
Which of the above equations correctly represent RSA cryptosystem?
I and II  
I and III  
II and IV  
III and IV 
1. Generate randomly two “large” primes p and q.
2. Compute n=pq and ∅=(p1)(q1).
3. Choose a number e so that
gcd(e,∅)=1
4. Find the multiplicative inverse of e modulo ∅, i.e., find d so that
ed≡1 (mod ∅)
This can be done efficiently using Euclid’s Extended Algorithm.
The encryption public key is K_{E}=(n,e) and the decryption private key is K_{D}=(n,d).
The encryption function is
E(M)=M^{e} mod n
The decryption function is
D(M)=M^{d} mod n
Question 6 
The total number of keys required for a set of n individuals to be able to communicate with each other using secret key and public key cryptosystems, respectively are:
n(n1) and 2n  
2n and n(n1)/2  
n(n1)/2 and 2n  
n(n1)/2 and n 
^{n}C_{2} = n(n1)/2
In case of public key, each sender has its own public key as well as private key. So, no. of keys are 2n.
Question 7 
Consider the following two statements:
(i) A hash function (these are often used for computing digital signatures) is an injective function.
(ii) An encryption technique such as DES performs a permutation on the elements of its input alphabet.
Which one of the following options is valid for the above two statements?
Both are false  
Statement (i) is true and the other is false  
Statement (ii) is true and the other is false  
Both are true 
ii) It uses the PBox permutation.
StatementI is false, II is true.
Question 8 
Your are given the following four bytes :
10100011 00110111 11101001 10101011Which of the following are substrings of the base 64 encoding of the above four bytes?
zdp  
fpq  
qwA  
oze 
10100011 00110111 11101001 10101011
So, in total we have 32 bits. And for base 64 we need 6 digits of binary no. to represent one digit of base 64 no.
So lets padd 4 bits on RHS, so that total digits will become 36 and we can separate then as group of 6 digits each.
Now, the longest substring will be from checking option is 'fpq'.
Question 9 
Which of the following statement(s) is TRUE?
1. A hash function takes a message of arbitrary length and generates a fixed length code.
2. A hash function takes a message of fixed length and generates a code of variable length.
3. A hash function may give the same hash value for distinct messages.
1 only  
2 and 3 only  
1 and 3 only  
2 only 
(2) Statement2 is wrong, refer statement1.
(3) Statement3 is correct, for example hash function N%10, this will generate same values for 1 as well as 2!
Question 10 
A sender is employing public key cryptography to send a secret message to a receiver. Which one of the following statements is TRUE?
Sender encrypts using receiver’s public key  
Sender encrypts using his own public key  
Receiver decrypts using sender’s public key  
Receiver decrypts using his own public key 
Question 11 
Is desirable property of the cryptographic algorithm  
Is undesirable property of the cryptographic algorithm  
Has no effect on the encryption algorithm  
None of the above 
→ In the case of highquality block cyphers, such a small change in either the key or the plaintext should cause a drastic change in the ciphertext.
Question 12 
You can control where traffic goes in the three networks  
You can do stateful packet filtering  
You can do load balancing  
Improve network performance 
1. The first firewall (also called the "frontend" or "perimeter" firewall) must be configured to allow traffic destined to the DMZ only.
2. The second firewall (also called "backend" or "internal" firewall) only allows traffic from the DMZ to the internal network.
This setup is considered more secure since two devices would need to be compromised. There is even more protection if the two firewalls are provided by two different vendors because it makes it less likely that both devices suffer from the same security vulnerabilities.
Question 13 
RSA Algorithm  
DiffieHellman Algorithm  
Electronic Code Book Algorithm  
None of the above 
Question 14 
Mutual authentication of client & server  
Secret communication  
Data Integrity protection  
Error detection and correction 
It is utilized to encrypt Web traffic using Hypertext Transfer Protocol (HTTP) and to authenticate Web servers, and to encrypt communications between Web browsers and Web servers etc.
So, other than error detection and correction, all options are correct.
Question 15 
X.25  
X.301  
X.409  
X.509 
Question 16 
his public key  
his private key  
receiver’s public key  
receiver’s private key 
Question 17 
64 bits  
128 bits  
512 bits  
1024 bits 
→ It can still be used as a checksum to verify data integrity, but only against unintentional corruption. It remains suitable for other noncryptographic purposes, for example for determining the partition for a particular key in a partitioned database.
Question 18 
IP packet with same header
 
IP packet with new header
 
IP packet without header
 
No changes in IP packet 
IPSec Tunnel mode: In IPSec Tunnel mode, the original IP packet (IP header and the Data payload) is encapsulated within another packet.
In IPSec tunnel mode the original IP Datagram from is encapsulated with an AH (provides no confidentiality by encryption) or ESP (provides encryption) header and an additional IP header. The IP addresses of the newly added outer IP header are that of the VPN Gateways.
The traffic between the two VPN Gateways appears to be from the two gateways (in a new IP datagram), with the original IP datagram is encrypted (in case of ESP) inside IPSec packet.
Question 19 
3  
7  
27  
40 
1. Choose two distinct prime numbers p and q.
2. Compute n = pq.
3. Compute λ(n) = lcm(λ(p), λ(q)) = lcm(p − 1, q − 1), where λ is Carmichael's totient function. Choose an integer e such that 1 < e < λ(n) and gcd(e, λ(n)) = 1; i.e., e and λ(n) are coprime.
4. Determine d as d ≡ e−1 (mod λ(n)); i.e., d is the modular multiplicative inverse of e modulo λ(n). This means: solve for d the equation d⋅e ≡ 1 (mod λ(n)).
Given two prime numbers are p = 5 and q = 11, encryption key, e = 27
n = p * q = 5 * 11 = 55
λ(n)= (p1) * (q1) = 4 * 10 = 40
Let the value of decryption key be ‘d’ such that:
e * d mod λ(n) = 1
27 * d mod 40 = 1
d = 3
Question 20 
Match the following symmetric block ciphers with corresponding block and key sizes :
ListI ListII (a) DES (i) block size 64 and key size ranges between 32 and 448 (b) IDEA (ii) block size 64 and key size 64 (c) BLOWFISH (iii) block size 128 and key sizes 128, 192, 256 (d) AES (iv) block size 64 and key size 128
(a)(iv), (b)(ii), (c)(i), (d)(iii)
 
(a)(ii), (b)(iv), (c)(i), (d)(iii)  
(a)(ii), (b)(iv), (c)(iii), (d)(i)  
(a)(iv), (b)(ii), (c)(iii), (d)(i) 
→ International Data Encryption Algorithm (IDEA), originally called Improved Proposed Encryption Standard (IPES), is a symmetrickey block cipher. It uses block size 64 and key size 128.
→ Blowfish is a symmetrickey block cipher used for a large number of cipher suites and encryption products. Blowfish provides a good encryption rate in software and no effective cryptanalysis of it has been found to date. It uses block size 64 and key size ranges between 32 and 448.
→ Advanced Encryption Standard(AES), which uses symmetric key method for encryption of data. It uses block size 128 and key sizes 128, 192, 256.
*****It’s worthy to remember below table.
Question 21 
Decrypt the message “WTAAD” using the Caesar Cipher with key = 15.
LIPPS
 
HELLO
 
OLLEH  
DAATW 
We decrypt one character at a time. Each character is shifted 15 characters up Letter W is decrypted to H shifted 15 characters up. Letter W is decrypted to H. Letter T is decrypted to E. The first A is decrypted to L. The second A is decrypted to L And finally D is The second A is decrypted to L. And, finally, D is decrypted to O. The plain text is HELLO.
Question 22 
Encrypt the Message “HELLO MY DEARZ” using Transposition Cipher with
HLLEO YM AEDRZ  
EHOLL ZYM RAED  
ELHL MDOY AZER  
ELHL DOMY ZAER 
Here, key size = 4. So, character block size is 4.
Step2: Remove the spaces in the message and write into sequential order.
Step3: Get cipher text according to ascending order is ELHL MDOY AZER.
Question 23 
Which of the following statement/s is/are true?
 (i) Firewall can screen traffic going into or out of an organization.
(ii) Virtual private networks cam simulate an old leased network to provide certain desirable properties.
Choose the correct answer from the code given below:
Code:(i) only  
Neither (i) nor (ii)  
Both (i) and (ii)
 
(ii) only 
Statement 2 is correct. Virtual private networks cam simulate an old leased network to provide certain desirable properties.
Question 24 
Suppose that everyone in a group of N people wants to communicate secretly with (N1) other people using symmetric key cryptographic system. The communication between any two persons should not be decodable by the others in the group. The number of keys required in the system as a whole to satisfy the confidentiality requirement is
2N  
N(N1)  
N(N1)/2
 
(N1)^{2}

→ We have N people in group so number of keys needed are N(N1).
→ But two people in a group can use same keys then no need to use 2(N1) keys they can communicate using (N1) keys.
So, total number of keys needed [N(N1)]/2.
Question 25 
Which of the following is NOT a symmetric key algorithm?
Ellipse Curve Cryptography
 
Advanced Encryption standard
 
Data Encryption Standard
 
Blowfish 
Question 26 
The traditional cryptographic cipher that records the letters but do not disguise them is:
Substitute cipher  
Onetime pads
 
Secret key algorithms
 
Transposition cipher 
Also this code can be easily broken.
Question 27 
Denial of service attack  
Masquerade attack  
Simple attack  
Complex attack 
→ A denialofservice attack (DoS attack) is a cyberattack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connected to the Internet.
Question 28 
Masquerade Attack  
Replay Attack  
Passive Attack  
Denial of Service Attack 
→ Replay involves the passive capture of a data unit and its subsequent retransmission to produce an unauthorized effect.
→ Passive attacks are very difficult to detect, because they do not involve any alteration of the data.Typically,the message traffic is sent and received in an apparently normal fashion,and neither the sender nor receiver is aware that a third party has read the messages or observed the traffic pattern.However,it is feasible to prevent the success of these attacks,usually by means of encryption.Thus,the emphasis in dealing with passive attacks is on prevention rather than detection.
→ The denial of service prevents or inhibits the normal use or management of communications facilities.This attack may have a specific target; for example, an entity may suppress all messages directed to a particular destination (e.g.,the security audit service).Another form of service denial is the disruption of an entire network,either by disabling the network or by overloading it with messages so as to degrade performance
Question 29 
A computer program  
Virus  
Computer professionals who solved complex computer problems.  
All of the above 
Question 30 
password encryption  
user  ID encryption  
authorization  
authentication 
Question 31 
Secure Electronic Transaction  
Secular Enterprise for Transaction  
Security Electronic Transmission  
Secured Electronic Termination 
→ SET was not itself a payment system, but rather a set of security protocols and formats that enabled users to employ the existing credit card payment infrastructure on an open network in a secure fashion.
Question 32 
2N  
N(N1)  
N(N1)/2  
(N1) _{2} 
→ We have N people in group so number of keys needed are N(N1)
→ But two people in a group can use same keys then no need to use 2(N1) keys they can communicate using (N1) keys.
So total number of keys needed [N(N1)]/2
Question 33 
Monoalphabetic  
Polyalphabetic  
Transpositional  
None of the above 
Polyalphabetic Substitution: This is an improvement over the Caesar cipher. In polyalphabetic substitution, each occurrence of a character may have a different substitute. Here the relationship between a character in the plaintext and a character in the ciphertext is always onetomany.
Transposition Cipher: The transposition cipher, the characters remain unchanged but their positions are changed to create the ciphertext. A transposition cipher does not substitute one symbol for another, instead it changes the location of the symbols. A transposition cipher reorders symbols.
Question 34 
(a)(iv), (b)(ii), (c)(i), (d)(iii)  
(a)(ii), (b)(iv), (c)(i), (d)(iii)  
(a)(ii), (b)(iv), (c)(iii), (d)(i)  
(a)(iv), (b)(ii), (c)(iii), (d)(i) 
→ International Data Encryption Algorithm (IDEA), originally called Improved Proposed Encryption Standard (IPES), is a symmetrickey block cipher. It uses block size 64 and key size 128.
→ Blowfish is a symmetrickey block cipher used for a large number of cipher suites and encryption products. Blowfish provides a good encryption rate in software and no effective cryptanalysis of it has been found to date. It uses block size 64 and key size ranges between 32 and 448.
→ Advanced Encryption Standard(AES), which uses symmetric key method for encryption of data. It uses block size 128 and key sizes 128, 192, 256
*****It’s worthy to remember below table.
Question 35 
Proves that she knows the secret without revealing it  
Proves that she doesn’t know the secret  
Reveals the secret  
Gives a challenge 
→ The simplest example of a challenge–response protocol is password authentication, where the challenge is asking for the password and the valid response is the correct password.
→ A more interesting challenge–response technique works as follows. Say, Bob is controlling access to some resource. Alice comes along seeking entry. Bob issues a challenge, perhaps "52w72y". Alice must respond with the one string of characters which "fits" the challenge Bob issued. The "fit" is determined by an algorithm "known" to Bob and Alice. (The correct response might be as simple as "63x83z" (each character of response one more than that of challenge), but in the real world, the "rules" would be much more complex.) Bob issues a different challenge each time, and thus knowing a previous correct response (even if it isn't "hidden" by the means of communication used between Alice and Bob) is of no use.
Question 36 
LIPPS  
HELLO  
OLLEH  
DAATW 
We decrypt one character at a time. Each character is shifted 15 characters up Letter W is decrypted to H shifted 15 characters up. Letter W is decrypted to H. Letter T is decrypted to E.The first A is decrypted to L. The second A is decrypted to L And finally D is The second A is decrypted to L. And, finally, D is decrypted to O.The plain text is HELLO
Question 37 
HLLEO YM AEDRZ  
EHOLL ZYM RAED  
ELHL MDOY AZER  
ELHL DOMY ZAER 
Here, key size=4. So, character block size is 4.
Step2: Remove the spaces in the message and write into sequential order.
Step3: Get cipher text according to ascending order is ELHL MDOY AZER.
Question 38 
5, 7, 15  
10, 12, 14  
5, 6, 7  
20, 12, 14 
→ The key size used for an AES cipher specifies the number of transformation rounds that convert the input, called the plaintext, into the final output, called the ciphertext.
→ The number of rounds are as follows:
1. 10 rounds with a key size of 128 bits.
2. 12 rounds with a key size of 192 bits.
3. 14 rounds with a key size of 256 bits.
Question 39 
protecting data in Data Communication System.  
reduce Storage Space Requirement.  
enhances Data Integrity.  
decreases Data Integrity. 
Question 40 
polyalphabetic  
monoalphabetic  
transpositional  
multi alphabetic 
Polyalphabetic Substitution: This is an improvement over the Caesar cipher. In polyalphabetic substitution, each occurrence of a character may have a different substitute. Here the relationship between a character in the plaintext and a character in the ciphertext is always onetomany.
Transposition Cipher: The transposition cipher, the characters remain unchanged but their positions are changed to create the ciphertext. A transposition cipher does not substitute one symbol for another, instead it changes the location of the symbols. A transposition cipher reorders symbols.
Question 41 
BUTAEEZ  
SUZANNE  
XYZABCD  
ABCDXYZ 
Φ = (p1)*(q1) = 20,
d = 7 and e = 3 (solve by e*d = 1 mod 20)
Message M= SUZANNE
Here take A = 1, B = 2, C = 3 ….. Z = 26, A = 27, …...
Cipher text = (M^{e} mod n)
⇒ S = 19, Cipher = 19^{3 }mod 33 = 28 = B
⇒ U = 21, Cipher = 21^{3} mod 33 = 21 = U
and so on ..
Question 42 
Layering  
Cryptography  
Grade of service  
None of the above 
Question 43 
Authenticity  
Non–Repudiability  
Auditability  
Repudiability 
Question 44 
Caesar cipher algorithm  
DES algorithm  
AES algorithm  
Knapsack algorithm 
→ Public key algorithms are Knapsack algorithm, RSA, Diffie Hellman,ECC,etc..,
Question 45 
Using ‘Z’ as bogus character.
TAXERTZENZ  
EXTRANETZZ  
EZXZTRZANZET  
EXTZRANZETZ 
 Plain text Message= EXTRANET
 Bogus character=Z
 Encrypt plain text message using Transposition cipher=?
Question 46 
Φ(n)=nπ_{pn}(1(1/p))
Where p runs over all the primes dividing n. What is the value of Φ(45)?
3  
12  
6  
24 
→ Φ(3^{2} * 5)
→ Φ(3^{2}) * Φ(5)
→ Φ(3^{2}  3,^{(21)}) * (51)
= 24
Remember Formula:
If p is prime then Φ(p) = (p1)
and if p is not prime and it's in prime power k from then Φ(p^{k}) = p^{k}  p(k1)
Question 47 
Intrusion detection systems  
Digital signatures  
Data Compression  
Certification 
Question 48 
S_{1} : For any integer n>1, a^{Φ(n)} = 1(mod n) for all a ∊ Z*_{n}, where Φ(n) is euler’s phi function.
S_{2} : If p is prime, then a^{p} = 1(mod p) for all a ∊ Z*_{p}
Which one of the following is are correct:
Only S_{1}
 
Only S_{2}  
Both S_{1} and S_{2}  
Neither S_{1 } nor S_{2} 
So the S1 is true.
According to Fermat's Little Theorem,
Let ‘p’ be a prime and ‘a’ any integer, then a^{p} = a (mod p). So S2 is false.
Question 49 
ManintheMiddle attack  
IP phishing
 
IP sniffing
 
IP Spoofing 
IP Spoofing: is the creation of Internet Protocol (IP) packets with a false source IP address, for the purpose of impersonating another computing system.
Question 50 
CTTOEWMROPNRUEK  
MROUEKCTTPNROEW  
OEWPNRCTTUEKMRO  
UEKPNRMROOEWCTT 
Question 51 
KEY  
Message  
Ciphertext  
User details  
OptionC and OptionD 
But it does not require User details.
Not relevant option"cipher text". Note: According to final answer key, given marks to optionC and OptionD
Question 52 
Consider the following statements with respect to network security:
(a) Message confidentiality means that the sender and the receiver expect privacy.
(b) Message integrity means that the data must arrive at the receiver exactly as they were sent.
(c) Message authentication means the receiver is ensured that the message is coming from the intended sender.
Which of the statements is (are) correct?
Only (a) and (b)  
Only (a) and (c)  
Only (b) and (c)  
(a), (b) and (c) 
TRUE: Message integrity means that the data must arrive at the receiver exactly as they were sent.
TRUE: Message authentication means the receiver is ensured that the message is coming from the intended sender.
Question 53 
The Data Encryption Standard (DES) has a function consists of four steps. Which of the following is correct order of these four steps?
an expansion permutation, Sboxes, an XOR operation, a straight permutation  
an expansion permutation, an XOR operation, Sboxes, a straight permutation  
an straight permutation, Sboxes, an XOR operation, an expansion permutation  
a straight permutation, an XOR operation, Sboxes, an expansion permutation 
Question 54 
Considering the following key using a block of five characters, encryption of the message "NETWORKING" using the Transposition Cipher is:
Plaintext : 5 4 3 2 1
Ciphertext 1 2 3 4 5
GNIKROWTEN  
OGWNTIEKNR  
OWTENGNIKR  
NREKTIWNOG 
→According to given question ,
→Plaintext : 5 4 3 2 1
→Ciphertext 1 2 3 4 5
→Given message "NETWO RKING".
→The message is divided into two equal messages of 5 characters length.
→According to cipher text, The reverse of 5 characters of message is OWTEN GNIKR
Question 55 
Consider an information exchange scenario where Anthony is the sender and Bond is the intended recipient of the data.
Match the following appropriately.
IC, IIB, IIID, IVA  
IC, IID, IIIA, IVB  
IC, IID, IIIB, IVA  
IA, IID, IIIB, IVC 
Message confidentiality: The transmitted message must make sense to only bond and to all others it must be garbage.
Message Integrity: The message must arrive at the bond’s side exactly as it was sent. Message Non Repudiation: Anthony must not be able to deny sending a message that he or she in fact, did send
Options C is correct.
Question 56 
“TINESAX / EOAHTFX / HTLTHEY / MAIIAIX / TAPNGDL / OSTNHMX”  
“TINESAX / EOAHTFX / MAIIAIX / HTLTHEY / TAPNGDL / OS TN HMX”  
“TINESAX / EOAHTFX / HTLTHEY / MAIIAIX / OSTNHMX / TAPNGDL”  
“EOAHTFX / TINESAX / HTLTHEY / MIIAIX / TAPNGDL / OSTNHMX” 
encrypt the message "The tomato is a plant in the nightshade family" using the keyword tomato. We get the grid given below.
We have written the keyword above the grid of the plaintext, and also the numbers telling us which order to read the columns in. Notice that the first "O" is 3 and the second "O" is 4, and the same thing for the two "T"s.
The plaintext is written in a grid beneath the keyword. The numbers represent the alphabetical order of the keyword, and so the order in which the columns will be read.
Starting with the column headed by "A", our ciphertext begins "TINESAX" from this column. We now move to the column headed by "M", and so on through the letters of the keyword in alphabetical order to get the ciphertext "TINESAX / EOAHTFX / HTLTHEY / MAIIAIX / TAPNGDL / OSTNHMX" (where the / tells you where a new column starts). The final ciphertext is thus "TINESAX EOAHTFX HTLTHEY MAIIAIX TAPNGDL OSTNHMX".
Question 57 
Large changes in cipher text when the keyword is changed minimally  
Large changes in cipher text when the plain text is changed  
Large impact of keyword change to the length of the cipher text  
None of the above 
Question 58 
substitution  
transposition  
substitution and transposition  
normalization 
Question 59 
Endtoend encryption  
Link encryption  
Combination of both link and endtoend encryption  
Either link encryption or endtoend encryption but not both 
Question 60 
SHA1 is used to generate hash code of message  
The hash code is prepended to the message and sent to the receiver  
The receiver uses RSA with senders public key to decrypt and recovered code  
Receiver generates a new hash code for the message and compares with the recovered code and accept the message as authentic, if only, they match 
Question 61 
RSA  
DiffieHellman key exchange  
Advanced Encryption Standard (AES)  
Elliptic Curve Cryptography (ECC) 
DiffieHellman key exchange algorithm is not at all a encryption algorithm ,instead it is a key exchange algorithm.
AES is a secret key encryption algorithm.
Question 62 
Circuit level gateways  
Application level gateways  
Packet filters  
Digital Immune System 
Application level gateways is also a type of firewall. Packet filtering is a firewall technique used to control network access by monitoring outgoing and incoming packets and allowing them to pass or halt based on the source and destination Internet Protocol (IP) addresses, protocols and ports.
The Digital Immune system is a comprehensive approach to virus protection, and is not a type of firewall.
Question 63 
A digital signature is
scanned signature
 
signature in binary form
 
encrypting information  
handwritten signature

Question 64 
A firewall is
an established network performance reference point
 
software or hardware used to isolate a private network from a public network
 
a virus that infects macros  
a predefined encryption key used to encrypt and decrypt data transmissions 
Question 65 
The private key in public key encryption is used for
encryption  
hashing
 
decryption  
decryption and hashing

Question 66 
Public key encryption makes use of
one key  
two keys  
hash function
 
All the given options 
Question 67 
In RSA
1. P and Q are chosen as very large prime number
2. Compute n = p*q and Φ(n) = (n1)*(q1)
Letter e encryption key chosen. How is this encryption key selected?
e is chosen as a relative prime to q
 
e is chosen as a relative prime to p  
e is chosen as a relative prime to Φ(n)
 
e is chosen as a relative prime to n

e*d = 1 mod Φ(n), where e is encryption key and d is decryption key.
Question 68 
Consider the following statement.
I. Packet filter firewall analyzes network traffic at transport layer.
II. Circuit level firewall operate transport and session layer of OSI model.
From the above statement which statement/s is/are TRUE?
Only I  
Only II  
None  
I and II

A circuitlevel gateway is a type of firewall. Circuitlevel gateways work at the session layer of the OSI model, or as a "shimlayer" between the application layer and the transport layer of the TCP/IP stack. They monitor TCP handshaking between packets to determine whether a requested session is legitimate.
Question 69 
___ is not a public key cryptosystem
EI Gemal
 
Rabin  
AES  
RSA

Like all asymmetric cryptosystems, the Rabin system uses a key pair: a public key for encryption and a private key for decryption. The public key is published for anyone to use, while the private key remains known only to the recipient of the message.
AES is a symmetric key cryptosystem or private key encryption.
RSA is one of the first publickey cryptosystems and is widely used for secure data transmission. In such a cryptosystem, the encryption key is public and distinct from the decryption key which is kept secret.
Question 70 
Digital certificates are described using ____ format.
X.509
 
X.510  
X.508  
X.409 
Question 71 
In RSA algorithm if p=7, q=11 and e=13 then what will be the value of d?
23  
40  
37  
13 
e * d ≡ 1 mod φ(n)
Lets first find φ(n),
φ(n) = (p1)(q1)
= (71)(111)
= 60
Now,
e * d ≡ 1 mod φ(n)
13 * d ≡ 1 mod 60
For d = 37 the above equation satisfies.
Question 72 
In____authentication, the claimant proves that she knows the secret without sending it to the verifier.
Asymmetric  
Zero knowledge
 
Symmetric  
Challenge response

In challenge response authentication, the claimant proves that she knows the secret without sending it to the verifier.
Question 73 
Consider following three statements about Data Encryption Standard (DES).
(I) DES uses a 56 bit key to encrypt 64 bit data blocks.
(II) DES is a Block cipher.
(III) DES provides Cipher Block Chaining mode to overcome the problem of poor diffusion.
The false statement from above statements is/are
Only (I)  
Only (I) and (III)  
Only (III)
 
None from (I), (II) and (III)

Hence all the statements are true.
Question 74 
Blowfish  
IDEA  
AES  
All the above 
Question 75 
Confidentiality and Integrity  
Authentication
 
Nonrepudiation
 
All the above 
IntegrityNo one can change the information. AuthenticationIt guarantees the identity of the sender. NonrepudiationNonrepudiation refers to the ability to ensure that a party to a contract or a communication cannot deny the authenticity of their signature on a document or the sending of a message that they originated. To repudiate means to deny.
Hence all are the security requirement.
Question 76 
John Richradson, John Smith and Len Adleman  
Ron Rivest, John Smith and L Hospital  
Ron Rivest, Adi Shamir and Len Adleman  
None of the above 
Question 77 
Digital Encryption Standard
 
Digital Encryption Specification
 
Data Encryption Standard  
Data Encryption Specification 
Question 78 
Data Security  
Data Integrity  
Data Redundancy  
(1) and (2) 
Question 79 
Publickey cryptography is also known as asymmetric cryptography  
Asymmetric cryptography uses a pair of cryptographic keys
 
A message encrypted with the private key can be decrypted only with the corresponding public key  
The private key is kept secret, while the public key is widely distributed 
Question 80 
Symmetric key cryptography is computationally infeasible.  
Symmetric key cryptography involves key distribution.  
Symmetric key cryptography is unreliable.  
Digital signature requires a pair of private – public keys. 
Question 81 
+ 3  
+ 2  
– 3  
– 2 
O2 = M
N  2 = L
G2 = E
R2 = P
A2 = Y
T2 = R
S2 = Q
Question 82 
(a) Masquerading (i) Session is intercepted (b) Phishing (ii) One pretends to be someone else (c) Hijacking (iii) A email misleads a user into entering confidential information Codes: (a) (b) (c)
(i) (ii) (iii)
 
(i) (iii) (ii)
 
(iii) (ii) (i)  
(ii) (iii) (i) 
PhishingPhishing is a cybercrime in which a target or targets are contacted by email, telephone or text message by someone posing as a legitimate institution to lure individuals into providing sensitive data such as personally identifiable information, banking and credit card details, and passwords.
HijackingHijacking is a type of network security attack in which the attacker takes control of a communication  just as an airplane hijacker takes control of a flight  between two entities and masquerades as one of them. So interception between two entities is done.
Question 83 
packet filter  
deep inspection firewall  
reverse proxy  
stateful packet inspection firewall 