mid exam practice quiz

Question 1 Study the scenario and complete the question(s) that follow: Ceasar Cipher The Caesar Cipher technique is one of the earliest and simplest method of encryption technique. It's simply a type of substitution cipher, i.e., each letter of a given text is replaced by a letter some fixed number of positions down the alphabet. For example with a shift of 1, A would be replaced by B, B would become C, and so on. The method is apparently named after Julius Caesar, who apparently used it to communicate with his officials. 1.1 Write a Ceasar cipher algorithm in such a way that a character D is changed to N. Derive the encryption of the other characters accordingly. 1.2 Based on your algorithm, what will be the encrypted code of the message “my mother is not home". End of Question 1

Draw your conclusion on this table below.

9. Correct and detailed answer. Handwritten solution not allowed. thanks

A government organization decides that in order to protect the communications it has with its international partners, encryption is necessary. In a discussion with its equivalents, it is decided to develop a proprietary cryptographic algorithm for the following reasons: Is this decision supported by any evidence. What dangers are being exposed?

true or false 11. One property of encryption algorithm is that someone can know the details of the algorithm and still not be able to decipher the encrypted message without knowing the key that the algorithm used to encrypt the message.

Part 1: Please answer the following questions about the fundamental of cryptography. Each question has only one correct answer.   1, Which description about block ciphers is NOT correct?  Block ciphers encrypt the message block by block. A block cipher with a small block is vulnerable to the codebook attack. The encryption and decryption algorithms in block ciphers use the same secret key. The key length for block cipher should be very short to defend against the exhaustive key search attacks.   2, If the key length of a block cipher is 64 bits, what is the size of the key space?  Hint: The key space consists of all possible keys. 64 264 232 2128   3, Modern block ciphers combine substitution S and permutation P operations to improve security. Based on the security rule, the cipher should not use consecutive substitutions or consecutive permutations.  In the following combinations, which one violates the above security rule?    ?1?1?2?2 B.  ?1?1?2?2 C.  ?1?1?2?2   4, Which…

6. Cryptography and Codes Decrypt the message AESO TTNO TTEH UASL ETRK EAHG KVDT EP if it was encrypted using a tabular transposition cipher with rows of length 6 characters.

Ciphertext or a cryptogram is an encoded message, or a message that has been successfully encrypted.. (A) True B) False

While attempting to decipher a short message, assaults on a cipher provide a greater challenge since they are more difficult to break.

1. In cryptography, the sender and receiver must always be known. (True or False)2. The process of decrypting a cipher is the same process in encrypting it. (True or False)

1. Asymmetric Encryption and Message Authentication:      a) The primitive root of a prime number is the basic principle of Diffie-Hellman.         i) Is 3 the primitive root of 11? Show the proof with your calculation.        ii) What are the important criteria for selecting a prime number in cryptography? Is 11 a good choice for such a purpose?    b) Find the parameters stated using the Diffie-Hellman methods, given the user A and B shared a prime number and its primitive root of 23 and 5, respectively.         i) If user A public key value is 8, find the A’s private key.        ii) If user B public key value is 19, what is the common secret key?   c) In the following scenario, we will compare the security services that are given by digital signatures (DS) and message authentication codes (MAC). We assume that James can read all messages send from Chan to Badrul and the other way around, too. James has no knowledge of any keys but the public one in the case of DS. State whether and…

Question # 1: Use the Affine cipher method to encrypt the following plaintext:Summer Term CompletedKey pair (K1, K2) = (5, 3) Remember: i need a Mathematics solution not computer program You must show all the steps of your work

Encryption/Decryption using RSA: Use p = 17, q = 11, and n = p*q = 17 × 11 = 187. φ(n) = (p - 1)(q - 1) = 16 × 10 = 160 PU = {7, 187} is the public key PR = {23, 187} is the private key Encrypt the plaintext message 80. What is the ciphertext message?   Question 10 options:   80   90   85   75

Question 9: Using public key cryptography, X adds a digital signature to message M, encrypts , and sends it to Y, where it is decrypted. Which one of the following sequences of keys is used for the operations? 1. Encryption: X's private key followed by Y's private key; Decryption: X's public key followed by Y's public key 2. Encryption: X's private key followed by Y's public key; Decryption: X's public key followed by Y's private key 3. Encryption: X's public key followed by Y's private key; Decryption: Y's public key followed by X's private key 4. Encryption: X's private key followed by Y's public key; followed by X's public key 01 02 03 04 Decryption: Y's private key EEVA KIEGO REJES

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(6) Using EIGamal Encryption Scheme, show encryption and decryption for the following message where the prime number is "p=71" and the generator is "lalpha=33". Message=12 Make sure to write every single step of your calculation.

Following are two problems using a rail fence cipher. Prove both of your answers by showing the steps involved in encryption/decryption.  As [art of this problem you must also show the steps involved in reversing what you are being asked for.  a.Using a rail fence cipher with a depth of 2 encrypt the following message: The bird is a raven b.Reverse the steps to decrypt your answer and explain the steps a. Using a rail fence cipher with zig zag pattern and a depth of 3 decrypt the following message:      MAEKN   ETTHPRAOEM  ETATP b.Reverse the steps to encrypt your answer and explain the steps.

Cryptography is the study of protecting information. A cipher is a pair of algorithms ―the first algorithm encrypts a message and the second algorithm decrypts the message. In most cases, a unique key is also required to encode or decode plaintext. The Caesar cipher is one of the simplest and most widely known ciphers. It is named after Julius Caesar who allegedly used it to protect important military directives. Every letter in the plaintext is replaced by a letter N positions down the alphabet. For example, if N = 3, then a => d and b => e. While the idea is remarkably simple, it appeared to work in Ancient Rome. Most people there couldn't read, and those who could simply assumed it was a foreign language. Write a program that implements the Caesar cipher. You program will get from standard input the key N, followed by a line of plaintext. . . The key N should be any integer between 0 and 26 inclusive. If this isn't the case, print an error message and quit. Any numbers or…

(c) The following table provides all possible block pairs of plaintext/ciphertext when using some block cipher E with a particular key K. Plaintext Ciphertext Plaintext 0000 1100 1000 1111 1001 0111 1010 1110 1011 1001 0010 1101 0001 0010 0011 0100 0101 0110 0111 1011 1100 1101 1110 1111 Ciphertext 0001 0000 0101 0100 0011 1000 0110 1010 Given that a plaintext P was encrypted using this block cipher operating in a counter mode starting with the counter value of 0, i.e. 0, 1, 2, ..., decrypt the ciphertext C = 010001110111.

q16) Name the authentication technique that uses public key cryptography between the sender and the receiver. a. Message Authentication Code b. None c. Hash functions d. Digital Signature

The following sentence describes steps that cryptographic code may perform to generate a ciphertext c and authentication tag t. “The message number i is concatenated with the message and encrypted with key Kenc to produce the ciphertext. The key Kauth is concatenated with i and with the message, and the resulting string is hashed with SHA3-384 to produce the tag.” Write the definitions of c and t as a formula

Using the two keys (memory words) cryptographic and network security, encrypt the following message:                  Be at the third pillar from the left outside the lyceum theatre tonight at seven. If you are distrustful bring two friends. Write your reasonable assumptions about how to treat redundant letters and excess letters in the memory words and how to treat spaces and punctuation. Indicate what your assumptions are. b. Decrypt the ciphertext. Show your work. c. Comment on when it would be appropriate to use this technique and what its advantages are

Public key cryptosystems are: (more than one may be true, choose all that are true) a offering a simpler way for key distribution B faster than symmetric C the preferred solution when the message we want to encrypt is very large D easily used to offer integrity E requiring advanced hardware in order to use them F easily used to offer confidentiality G marketed better than symmetric that is why people prefer them H using one key for encryption and a different key for decryption

4. El-Gamal O Consider the El-Gamal encryption scheme and let p = 19 and 9 = 3 (a) Suppose the private key is x = 7. Compute the public key y. (b) Encrypt the message M = 8 using the public key above and r = 8. (c) Verify your calculation in part (b) above by decrypting the ciphertext you obtained in part (b)

Respond to the question with a concise and accurate answer, along with a clear explanation and step-by-step solution, or risk receiving a downvote.   Please explain correct and incorrect option

Given the prime factors p and q, the encryption exponent e, and the ciphertext C, apply the RSA algorithm to find (a) the decryption exponent d and (b) the plaintext message M. C b. 55 17 5 e 73 (a) The smallest natural number for the decryption exponent d is (b) The plaintext M is

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5. Use RSA public-key encryption to decrypt the message 111 using the private keys n = 133 and d = 5.