Network-Security
Question 1 |
The value of 351 mod 5 is ______.
3 | |
5 | |
2 | |
1 |
⇒ 31 = 3 ⇒ 3 mod 5 = 3
32 ⇒ 9 mod 5 = 4
33 ⇒ 27 mod 5 = 2
34 ⇒ 81 mod 5 = 1
35 ⇒ 243 mod 5 = 3
For every four numbers sequence is repeating.
So, (51 % 4) = 3
⇒ 33 = 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,
x2 − (p+q)x + pq = (x-p)(x-q)
Substituting for p+q and pq in the above equation
x2 - (n+1-ϕ(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 layer-4 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 multi-user 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)(q-1). Now consider the following equations.
I. M’= Me mod n M = (M’)d mod n II. ed ≡ 1 mod n III. ed ≡ 1 mod f(n) IV. M’= Me 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 ∅=(p-1)(q-1).
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 KE=(n,e) and the decryption private key is KD=(n,d).
The encryption function is
E(M)=Me mod n
The decryption function is
D(M)=Md 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 crypto-systems, respectively are:
n(n-1) and 2n | |
2n and n(n-1)/2 | |
n(n-1)/2 and 2n | |
n(n-1)/2 and n |
nC2 = n(n-1)/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 P-Box permutation.
Statement-I 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) Statement-2 is wrong, refer statement-1.
(3) Statement-3 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 high-quality 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 "front-end" or "perimeter" firewall) must be configured to allow traffic destined to the DMZ only.
2. The second firewall (also called "back-end" 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 | |
Diffie-Hellman 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 non-cryptographic 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)= (p-1) * (q-1) = 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 :
List-I List-II (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 symmetric-key block cipher. It uses block size 64 and key size 128.
→ Blowfish is a symmetric-key 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.
Step-2: Remove the spaces in the message and write into sequential order.

Step-3: 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 (N-1) 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(N-1) | |
N(N-1)/2
| |
(N-1)2
|
→ We have N people in group so number of keys needed are N(N-1).
→ But two people in a group can use same keys then no need to use 2(N-1) keys they can communicate using (N-1) keys.
So, total number of keys needed [N(N-1)]/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 | |
One-time 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 denial-of-service attack (DoS attack) is a cyber-attack 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(N-1) | |
N(N-1)/2 | |
(N-1) 2 |
→ We have N people in group so number of keys needed are N(N-1)
→ But two people in a group can use same keys then no need to use 2(N-1) keys they can communicate using (N-1) keys.
So total number of keys needed [N(N-1)]/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 one-to-many.
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 symmetric-key block cipher. It uses block size 64 and key size 128.
→ Blowfish is a symmetric-key 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.
Step-2: Remove the spaces in the message and write into sequential order.

Step-3: 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 one-to-many.
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 = (p-1)*(q-1) = 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 = (Me mod n)
⇒ S = 19, Cipher = 193 mod 33 = 28 = B
⇒ U = 21, Cipher = 213 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)=nπp|n(1-(1/p))
Where p runs over all the primes dividing n. What is the value of Φ(45)?
3 | |
12 | |
6 | |
24 |
→ Φ(32 * 5)
→ Φ(32) * Φ(5)
→ Φ(32 - 3,(2-1)) * (5-1)
= 24
Remember Formula:
If p is prime then Φ(p) = (p-1)
and if p is not prime and it's in prime power k from then Φ(pk) = pk - p(k-1)
Question 47 |
Intrusion detection systems | |
Digital signatures | |
Data Compression | |
Certification |

Question 48 |
S1 : For any integer n>1, aΦ(n) = 1(mod n) for all a ∊ Z*n, where Φ(n) is euler’s phi function.
S2 : If p is prime, then ap = 1(mod p) for all a ∊ Z*p
Which one of the following is are correct:
Only S1
| |
Only S2 | |
Both S1 and S2 | |
Neither S1 nor S2 |
So the S1 is true.
According to Fermat's Little Theorem,
Let ‘p’ be a prime and ‘a’ any integer, then ap = a (mod p). So S2 is false.
Question 49 |
Man-in-the-Middle 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 | |
Option-C and Option-D |
But it does not require User details.
Not relevant option-"cipher text". Note: According to final answer key, given marks to option-C and Option-D
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, S-boxes, an XOR operation, a straight permutation | |
an expansion permutation, an XOR operation, S-boxes, a straight permutation | |
an straight permutation, S-boxes, an XOR operation, an expansion permutation | |
a straight permutation, an XOR operation, S-boxes, 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.

I-C, II-B, III-D, IV-A | |
I-C, II-D, III-A, IV-B | |
I-C, II-D, III-B, IV-A | |
I-A, II-D, III-B, IV-C |
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 |
End-to-end encryption | |
Link encryption | |
Combination of both link and end-to-end encryption | |
Either link encryption or end-to-end encryption but not both |
Question 60 |
SHA-1 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 | |
Diffie-Hellman key exchange | |
Advanced Encryption Standard (AES) | |
Elliptic Curve Cryptography (ECC) |
Diffie-Hellman 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) = (n-1)*(q-1)
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 circuit-level gateway is a type of firewall. Circuit-level gateways work at the session layer of the OSI model, or as a "shim-layer" 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 public-key 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) = (p-1)(q-1)
= (7-1)(11-1)
= 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
| |
Non-repudiation
| |
All the above |
Integrity-No one can change the information. Authentication-It guarantees the identity of the sender. Non-repudiation-Nonrepudiation 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 |
Public-key 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 |
O-2 = M
N - 2 = L
G-2 = E
R-2 = P
A-2 = Y
T-2 = R
S-2 = 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) |
Phishing-Phishing 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.
Hijacking-Hijacking 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 |