1. Let (01, 02, 03,..., 026!} be the set of permutations of the alphabetA = {A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z},and consider the simple substitution cryptosystem withok =A B C D E F G H I J K L MX MTAK ZQB NO LESN O P Q R S T U V W X Y ZIF G R V JH CY UDP Wand key k.(a) Compute C = e(AUBUR NUNIV ERSIT YATMO NTGOM ERY, k).(b) Compute M = d(NIZFV SXHNF IHBKF VPXIA KIHVF GP, k).

Given : (a) Compute C = e(AUBUR NUNIV ERSIT YATMO NTGOM ERY, k). (b) Compute M = d(NIZFV SXHNF IHBKF…

Answered: 1. Let {01, 02, 03, ..., 026!} be the…

Computer Networking: A Top-Down Approach (7th Edition)

7th Edition

ISBN:9780133594140

Author:James Kurose, Keith Ross

Publisher:James Kurose, Keith Ross

Chapter1: Computer Networks And The Internet

Section: Chapter Questions

Problem R1RQ: What is the difference between a host and an end system? List several different types of end...

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Use a computer to plot formula 2.22 directly, as follows. Define z = qA/q, so that (l-z) = qB/q. Then, aside from an overall constant that we'll ignore, the multiplicity function is [4z(1-z)]N, where z ranges from 0 to 1 and the factor of 4 ensures that the height of the peak is equal to 1 for any N. Plot this function for N = 1, 10, 100, 1000, and 10,000. Observe how the width of the peak decreases as N increases.
Exercise 2 (MAC schemes derived from block ciphers( Let E denote the family of encryption functions for a block cipher where plaintext blocks, ciphertext blocks, and keys are each n = 80 bits in length. Let H {0, 1} {0, 1}" be a hash function. Assume that plaintext messages m all have bit-lengths that are multiples of n; we write m = (my, m₂,...,m), i.e. m is composed of t blocks m, of n bits each. Consider the following MAC schemes, each using an n-bit secret key k. 1. MAC (m) = ₁, where co = 0, and c, =c-1m, Ex(m) for 1 ≤ i ≤t. 2. MAC (m) Ek(H(m)). Are any of these MAC schemes secure? Justify your answer and clearly state any assumptions you make.
3. For this task you are going to generate a key and use stream cipher. (a) Use the quadratic residue pseudorandom generator (BBS)on the prime numbers p and q of your choice, where 5000 < p, q < 9000, to generate the first five bits of your key k0, k1, k2, k3 and k4. (b) Generate a key sequence of length 40 by using the recurrence relation xn+5 = xn+4 + xn+2 + xn+1 + xn (mod 2), n ≥ 0 where the initial values are the key generated in (a). (c) Encode your last name by using the ASCII code. Use the stream cipher and the key you generated above to encrypt your last name.
Is it consistent to say that a hash table of size m always contains the same number of linked lists? I've been trying to understand the purpose of a hash function for ages. Give an illustration of your point with an example.
The Java hash function for Strings computes a hash code based on a fixed maximum number of characters of the string. Given that Strings have no meaningful upper bound in length, describe how an effective, constant-time hashing algorithm can be constructed. (Hint: If you were to pick, say, eight characters to represent a string of length l, which would you choose?)
13(a) Consider the alphabet Σ = {a,3,7,6}. Answer the following two questions. You must justify your answers, and not simply state numerical values. (i) How many strings of length 5 defined over Σ contain exactly one a and exactly one 3? (ii) How many strings of length 5 defined over Σ contain exactly two y's and at least one d?
A cryptanalyst has determined that the three most common trigraphs in a ciphertext are LME, WRI, and ZYC, and guesses that these ciphertext trigraphs correspond to the three most common trigraphs in English text, THE, AND, and THA. If the plaintext was encrypted using a Hill trigraphic cipher described by C ≡ AP (mod 26), what are the entries of the 3 × 3 encrypting matrix A?
Shouldn't the number of paths from D to E be C(6,2) and from E to C be C(4,2)?
Please see attached
Cryptographic Data ObjectsB has just received the following message, which represents a cryptographic data object:{({(KPbB)KPrS mod KPbS}K1,{|(NB, NA, {{({K2}KPbB, NS)}(G1)KPrA mod NA}K1, {|{({G3}(KPbA)KPrS mod KPbS, G2)}K1|}KPrB)|}KPrA)}KBSThe following explains various terms in this object and some of the abbreviations used:• {M}K represents the encryption of some message/data M using the key K• {|M|}K represents the digital signing of some message/data M using the key K• NX represents a nonce (i.e. a fresh and possibly random number used once only) generatedby X• KpbX represents the public part of the key pair presumably owned by X• KprX represents the private part of the key pair presumably owned by X• KAB represents a symmetric key shared between A and B• K (or K1, K2, K3 etc.) represents some arbitrary key with no assumptions about its scope• M represents some alphanumeric/textual message with no assumptions• G1, G2, G3 etc. are prime numbersWhich of the following sets of keys,…
Is it true that for any nfa M = (Q,E,8.90,F) the complement of L(M)is equal to the set {w e E*: 8* (40,w) n. F= Ø}? If so, prove it. If not, give a counterexample. Is it true that for every nfa M = (Q, £,8,40.F)the complement of L (M)is equal to the set {w e £* : 8*; (g0,w) e (Q – F) = Ø}? If so, prove it; if not, give a counterexample.
In §12.2 Lamport's Hash we mentioned the notion of using only 64 bits of the hash. At each stage, 128 bits are computed, 64 bits are thrown away, and the hash of the retained 64 bits is used in the next stage. The purpose of only using 64 bits is so that a human does not need to type as long a string. Assuming the person will still only type 64 bits, does it work if hashn does a hash of all 128 bits of hashn-1, but what the person actually transmits is 64 bits of the result?

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