# Recent questions tagged network-security

1
Using ‘RSA’ public key cryptosystem, if $p=3$, $q=11$ and $d=7$, find the value of $e$ and encrypt the number $’19’$ $20, 19$ $33,11$ $3, 28$ $77, 28$
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Which among the following statement(s) is(are) true? A hash function takes a message of arbitrary length and generates a fixed length code A hash function takes a message of fixed length and generates a code of variable length A hash function may give same hash value for distinct messages Choose the correct ... options given below: $(a)$ only $(b)$ and $(c)$ only $(a)$ and $(c)$ only $(b)$ only
1 vote
3
Firewall is a device that filters access to the protected network from the outside network. Firewalls can filter the packets on the basis of Source IP address Destination IP address TCP Source Port UDP Source Port TCP Destination Port Choose the correct answer from the options given below: $(a), (b)$ and $(c)$ only $(b)$ and $(e)$ only $(c)$ and $(d)$ only $(a), (b), (c), (d)$ and $(e)$ only
4
Given below are two statements: Statement $I$: In Ceasar Cipher each letter of Plain text is replaced by another letter for encryption Statement $II$: Diffie-Hellman algorithm is used for exchange of secret key In the light of the above statements, choose the correct answer ... $I$ is correct but Statement $II$ is false Statement $I$ is incorrect but Statement $II$ is true
1 vote
5
How many bits are required to encode all twenty six letters, ten symbols, and ten numerals? $5$ $6$ $7$ $46$
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$PGP$ encrypts data by using a block cipher called : international data encryption algorithm private data encryption algorithm internet data encryption algorithm none of the options
1 vote
7
Why is one - time password safe ? It is easy to generate It cannot b shared It is different for every access It can be easily decrypted
1 vote
8
The ability to inject packets into the Internet with a false source address is known as Man-in-the-middle attack IP phishing IP sniffing IP spoofing
1 vote
9
The RSA encryption algorithm also works in reverse, that is, you can encrypt a message with the private key and decrypt it using the public key. This property is used in instruction detection systems digital signatures data compression certification
10
A math class has 25 students. Assuming that all of the students were born in the first half of the year—between January 1st and June 30th— what is the probability that at least two students have the same birthday? Assume that nobody was born on leap day, so there are 181 possible birthdays.
11
33. Two users can establish a shared secret key using the Diffie-Hellman algorithm, even if they have never met, share no secrets, and have no certificates (a) Explain how this algorithm is susceptible to a man-in-the-middle attack. (b) How would this susceptibility change if n or g were secret?
12
The Diffie-Hellman key exchange is being used to establish a secret key between Alice and Bob. Alice sends Bob (227, 5, 82). Bob responds with (125). Alice’s secret number, x, is 12, and Bob’s secret number, y, is 3. Show how Alice and Bob compute the secret key.
13
Alice wants to communicate with Bob, using public-key cryptography. She establishes a connection to someone she hopes is Bob. She asks him for his public key and he sends it to her in plaintext along with an X.509 certificate signed by the root CA. Alice already has the public key ... is talking to Bob? Assume that Bob does not care who he is talking to (e.g., Bob is some kind of public service).
14
Alice and Bob use RSA public key encryption in order to communicate between them. Trudy finds out that Alice and Bob shared one of the primes used to determine the number n of their public key pairs. In other words, Trudy found out that na = pa × q and nb = pb × q. How can Trudy use this information to break Alice’s code?
1 vote
15
Using the RSA public key cryptosystem, with a = 1, b = 2 . . . y = 25, z = 26. (a) If p = 5 and q = 13, list five legal values for d. (b) If p = 5, q = 31, and d = 37, find e. (c) Using p = 3, q = 11, and d = 9, find e and encrypt ‘‘hello’’.
16
I'm not able to distinguish the difference between digital certificate and digital signature Correct me if there is flaw in my understanding : A Digital Certificate is certificate of authenticity and it is given to any host by a trusted third party which leases it ... on the other hand is dished out by the client/server whenever it attempts to make any data transfer and it ensure data integrity
17
In an RSA cryptosystem, the value of the public modulus parameter $n$ is $3007$. If it is also known as that $\phi(n)=2880$ where $\phi()$ denotes Euler’s Totient Function, then the prime factor of $n$ which is greater than $50$ is _________
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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 $N(N-1)$ $N(N-1)/2$ $2N$ $(N-1)^2$
20
It is impossible to produce a document that differs from the original document with single bit change and valid signature I am unable to understand, why is it impossible? bit changing is one way of intruder to steal information.right? plz give some valid reason
21
Which of the following is TRUE with respect to Diffie-Hellman Key exchange algorithm? It can be used for encryption or decryption purpose It doesn't suffer from man in the middle attack It suffers from bucket brigade attack It is an example of private key cryptography algorithm
22
From a large set of prime numbers Jimmy choose 23 and 17 as P and Q respectively and a random integer to be 13. Jimmy wants to sends a plain text to M = 127. What will be the value of cipher text using RSA? since i am getting ciphertext =(127^13) mod 391 now how should i calculate
23
Let M be a confidential email that Alice wants to send to Bob, $K_B$ be Bob's encryption public key, and $K_A^{-1}$ be Alice's private key for signing. Which of the following options would be the best choice for protecting confidential emails? ... Encrypted message, Alice should sign the encrypted message and then should send this signature along with the encrypted message to BOB. Please help.
24
Consider RSA with p = 31 and q = 47. I. n = 1457 II. z= 1200 III. 7 is acceptable choice for e Which of the following is true ? A. Only I B. Only I and II C. Only I and III D. All of I,II and II I am Getting answer (C), but answer is given (D). As per kurose Ross, Z is defined to be $(p-1)(q-1)$
1 vote
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suppose that a message has been encrypted using DES in chipertext block chaining mode. One bit of chipertext in block Ci is accedntally transformed from 0to 1during transmissin. How much plaintext will be grabled as a result? a)1 b)2 c)n- d)n-i+1