Note: The notation from this problem is from Understanding Cryptography by Paar and Pelzl.We conduct a known-plaintext attack against an LFSR. Through trial and error we have determined that the number ofstates is m =4.The plaintext given by11000101 — ХоXјX2XҙХ4X5X6X7when encrypted by the LFSR produced the ciphertext10010000Уo У1 У2 Уз Уз У5 У6 Ут .What are the tap bits of the LFSR? Please enter your answer as unspaced binary digits (e.g. 0101 to representP3 = 0, p2 = 1, p1 = 0, po = 1).

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Answered: Note: The notation from this problem is…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Note: The notation from this problem is from Understanding Cryptography by Paar and Pelzl. Consider the LFSR represented by the polynomial x4+x2+1x4+x2+1. What are the tap bits of the LFSR? Please enter your answer as unspaced binary digits (e.g. 010101 to represent p5=0,p4=1,p3=0,p2=1,p1=0,p0=1p5=0,p4=1,p3=0,p2=1,p1=0,p0=1).
A shortcoming of using an elliptic curve E(Fp) for cryptography is the fact that it takes two coordinates to specify a point in E(Fp). However, as discussed briefly at the end of Sect. 6.4.2, the second coordinate actually conveys very little additional information.(b) Alice and Bob decide to use the prime p = 1123 and the elliptic curveE : Y2 = X3 + 54X + 87.Bob sends Alice the x-coordinate x = 278 and the bit β = 0. What point is Bob trying to convey to Alice? What about if instead Bob had sent β = 1?
Problem #1Given below is a well-known cryptosystem called affine Caesar cipher, as well as someciphertext generated using the affine Caesar cipher.P = C = Z 26 = {0, 1, 2, ..., 25};K = {(a, b) Z26 Z26 | gcd(a, 26) = 1}y = E([a,b], x) = (ax + b) mod 26,x = D([a,b], y) = a-1 (y – b) mod 26,where x P, y C. Ciphertext sample:VPWOMFUWOFMYMHUNWBBWGCRVVPSFVPUTHUJWMCOMFUOVSVWOVWGSRSFSREOWOQMHKOBMHVPWOUFGHETVWMFOEOVUYVMMZCVGSFEMCCOUEMCHKFMQRUNIUMBRWFUSHSRIUZHSVMBWFNVPUOUGHUVKUEVMMVPUFEMCQWRRPSJUVHCREGHSGKUNVPUOEOVUY For this problem, please do the following:(a) provide an analysis detailing its strength/weakness;(b) attempt to uncover the plaintext associated with the ciphertext;(c) attempt to determine the secret key (a, b) used.
Alice and Bod have decided to use a symmetric encryption algorithm. They have some assumptions about their messages:- Messages only contain capital letters (i.e. A to Z)- The length of their shared key must be greater than or equal to the length of the plaintext- They assign each letter a number as follows: (A,0), (B,1), (C,2), (D,3),…, (Z,25)Their algorithm combines the key and the message using modular addition. The numerical values of corresponding message and key letters are added together, modulo 26. For example, if the plain text is “HELLO” and the key is “SECRET” then the encrypted message is calculated as following:Since the length of the plaintext is 5, we just need the first 5 letters of the key (i.e. “SECRE”), then for each letter, we should add corresponding letters in both the plaintext and the key modulo 26.Plaintext: H (7) E (4) L (11) L (11) O (14)Key: S (18) E (4) C (2) R (17) E(4)Cipher: Z (25) I (8) N(13) C(2) S (18) Write a program in Python, C/C++ or JavaScript to…
Let Π = (Gen,Enc,Dec) be a private-key encryption scheme that has indistinguishable en- cryptions in the presence of an eavesdropper. Which of the following encryption schemes are also necessarily secure against an eavesdropper? If you think a scheme is secure, sketch a proof, if not, provide a counterexample. Here, for a bit string s, parity(s) is 1 if the number of 1’s in s is odd, and 0 otherwise. The || symbol stands for concatenation. So, for strings if x = 00 and y = 11, x||y = 0011. (a) Enc1k(m) = 0||Enck(m)(b) Enc2k(m) = Enck(m)||parity(m) (c) Enc3k(m) = Enck(m)||Enck(m)(d) Enc4k(m) = Enck(m)||Enck(m + 1). Here think of m as an integer. Please type answer note write by hend.
Alice and Bod have decided to use a symmetric encryption algorithm. They have someassumptions about their messages:- Messages only contain capital letters (i.e. A to Z)- The length of their shared key must be greater than or equal to the length of the plaintext- They assign each letter a number as follows: (A,0), (B,1), (C,2), (D,3),…, (Z,25)Their algorithm combines the key and the message using modular addition. The numerical valuesof corresponding message and key letters are added together, modulo 26. For example, if the plaintext is “HELLO” and the key is “SECRET” then the encrypted message is calculated as following:Since the length of the plaintext is 5, we just need the first 5 letters of the key (i.e. “SECRE”), thenfor each letter, we should add corresponding letters in both the plaintext and the key modulo 26.Plaintext: H (7) E (4) L (11) L (11) O (14)Key: S (18) E (4) C (2) R (17) E(4)Cipher: Z (25) I (8) N(13) C(2) S (18) a) Write a program in Python, C/C++ or JavaScript to…
The problem at the center of RSA is finding the e’th root of the ciphertext c modulo N where N = pq is a product of (distinct) primes. This is hard to do for large N if you don’t know the factors p and q, but once you know p and q it becomes easy! Write a finction findRoot(c,e,p,q) which solves the equation xe ≡ c mod N for x where N = pq
1. Suppose that we use a substitution cipher to encrypt an English word, from which we obtain the ciphertext is “AUXXME”. Which of the following words is possibly the plaintext? (Hint: In a substitution cipher, we replace each letter of the plaintext with another letter) A. greedy B. funny C. secret D. cheese 2. Which of the following statements are incorrect? A. Cryptographic systems tend to involve both an algorithm and a secret value. B. To secure systems, it is more efficient to update algorithms than updating keys. C. Often a scheme can be made more secure by making the key longer. D. We can always change the key length to better secure systems, no matter using which cryptographic algorithms. E. In a secret-key cryptosystem, secret keys can be used for both encryption and decryption. 3. Which of the following statements are incorrect about a cryptographical hash function? A. The input size can be arbitrary and the output size is fixed B. Given the input, the output should…
In a special case of a permutation cipher, we take a message, M, and write its letters in an s× t table, in a row-major fashion, and then let the ciphertext be a column-major listing of the entries in the table. For example, to encrypt the message ATTACKATDAWN, using a 3 × 4 table, we would write the message as ATTA CKAT DAWN and then write down the ciphertext as ACDTKATAWATN. The secret key in this cryptosystem is the pair (s, t). How is decryption done in this cryptosystem? Also, how hard would it be to attack this cryptosystem using a ciphertext-only attack?
1.Give the decryption of the following messages that have been encrypted with the key 4551. You should get readable messages. a. RTYAWJHVVJ b. WYFUMXYJGX c. VTRFS_NMPJEJPQNOSNX 2.Say you obtain a ciphertext of an English sentence encrypted with an unknown key using the same four-digit shift scheme as problems 8 and 9. For a brute-force attack, what is the maximum number of keys would you have to test?
Problems are on this Textbook: Stallings, W. (2019). Cryptography and Network Security (8/E). Pearson Publishing. ISBN: 978-0-13576-403-9 7.10 In discussing the CTR mode, it was mentioned that if any plaintext blocks that is encrypted data using a given counter value is known, then the output of the encryption function can be determined easily from the associated cipher text block. SHow the calculation.
How would you solve part a and b? This is an applied cryptography type question. a. Suppose ' = 2, so r can be from the set {0,1,2,3}. Assume you, the eavesdropper, gets the sequence: 145471,25245,14596,143468,153125 encrypted via the padded RSA scheme using (N,e) = (157439,5). Without decrypting, find the sequence of votes. b. Suppose now that ' = 100, so r can be from the set {0,1}100. What is the time complexity of your attack from part (a)? Is it feasible? If you were an employee, would you recommend this scheme to the CEO?

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