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, E(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.

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, E(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.

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

See similar textbooks

Related questions

Q: a) Why is Hashing preferred over other method of searching? b) Explain the differences between open…

A: Answer the following questions: a) What is the reason for preferring Hashing as a searching method…

Q: 1: (Brute-Force String Matching) Determine the exact number of character comparisons made by…

A: We need to apply the brute forces string on the above text. See below step for explanation.

Q: (V13-1) This type of divisive a) Consider a hash table of size m = 1000 and a corresponding hash…

A: Please refer to the following steps for the complete solution to the problem above.

Q: Assume an open addressing hash table implementation, where the size of the array is N = 19, and that…

A: In this question we have to understand about the handling collisions and determining specific…

Q: 3. Consider an example of hash table of size 30, and the following items are to be stored. Design…

Q: Given a hashing function hash(x) = ((x * x) + x) % 11, Insert the value 17 into each hash table…

A: Note since this question contain multiple sub question so we are providing answer to first 2…

Q: E segment. new double [M] [N]; B = new double [M] [N]; A +th

A: #include<stdio.h> int main() { /* 2D array declaration*/ int disp[2][3]; /*Counter…

Q: Let B be the set of all binary strings of length 8. {“00000000”, “00000001”, … “11111110”,…

A: Binary numbers, commonly known as "binary," form a numerical system extensively utilized in the…

Q: 1. (4 points) Suppose we have a hash table of size 29 and we want to implement a system for looking…

A: 1. (4 points) Suppose we have a hash table of size 29 and we want to implement a system for…

Q: Computer Science D Question 9 What is the probability of having a 64-bit hash value with the…

A: Ans 9. We know Probability= No. Of Favourable Cases/ Total No. Of Cases Here, Total No. Of Cases…

Q: b) Consider an empty hash table of size 7. Draw the table that results after inserting, in the given…

A: The answer is as follows:-

Q: Given an m x n binary matrix mat , return the distance of the nearest 0 for each cell. The distance…

A: Solution in python: Python code: # Python3 program to find distance of# nearest cell having 0 in…

Q: Assume we wish to resize an existing hash table because the current hash table is becoming too small…

A: Below are the steps required to copy the data from the old hash table to the new hash table and…

Q: Write a C program mexp that multiplies a square matrix by itself a specified number of times. mexp…

A: #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { if (argc != 2)…

Q: Suppose Alice computes the Secret suffix MAC (page 322: secret suffix MAC(x) = h(x || key)) for the…

A: Alice Clicks on a link on Bob’s bookstore website to check on a price. Bob Sends the webpage (not…

Q: Suppose that extendable hashing is being used on a database file that contains records with the…

Question

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.

Expert Solution

This question has been solved!

Explore an expertly crafted, step-by-step solution for a thorough understanding of key concepts.

This is a popular solution!

SEE SOLUTION Check out a sample Q&A here

Step 1

VIEW

Step 2

VIEW

Trending now

This is a popular solution!

Step by step

Solved in 2 steps

SEE SOLUTION Check out a sample Q&A here

Knowledge Booster

Learn more about

Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, computer-science and related others by exploring similar questions and additional content below.

Similar questions

3. Consider an example of hash table of size 30, and the following items are to be stored. Design the hash table and the final array in the obtained indexes. (14, 22) (11, 18) (52,71) (41, 20) (30, 29) (33,64)
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.
Problem 3: We want to create a string of length n from the following blocks of letters: A, B, TK, CC, DD, EE. (a) Let P₁ denote the number of such blocks. For example, AAAB, ABEE and DDCC are blocks of length 4. Set up and justify the recurrence for Pn. (Make sure to provide the initial conditions). (b) Let T₁ denote the number of such words, in which blocks A and CC can't be next to each other (no ACC or CCA), no three A's and no two blocks of CC's in a row (no AAA or CCCC). For example, ABCCDD and CCEEEE are valid strings of length 6, while CCBAAA, BCCABB and CCCCDD are not. Set up and justify the recurrence for T How many initial conditions do you need to know in order to solve the recurrence? Give only the first two initial conditions.
Can you give me example of quadratic probing in C++ ? The quadratic problem function has one input, call it m where m is a int. The return type is an int. For example, you have the serial number 2232012, quadProb(2232012) will return an int. Assume that the hash table size is 450. Assume that you are working with an uninitialized 2D array. Also write an insert() function to populate this 2D array.
9.10. Let F be a secure block cipher with blocklength 2. Below is an encryption scheme for plaintexts M = {0, 1}². Formally describe its decryption algorithm and show that it does not have CCA security. Enc(k, m): re {0,1}^ c1 := F(k,r) C2 := r F(k, m) return (c1, c2) KeyGen: k + {0, 1}^ return k
Computer science question
Task - 1: Write a java program to implement the following algorithms for Open Addressing techniques for Hash Table data structure. (Use a simple array of integers to store integer key values only). HASH-SEARCH(T, k) HASH-INSERT (T, k) i = 0 repeat j = h (k, i) if T[j] == NIL T[j] = k return j else i = i + 1 ● i = 0 repeat until i == m error “hash table overflow" For both algorithms, to compute the index j, write the following methods: getLinear ProbIndex (key, i) getQuadraticProbIndex ● get DoubleHash (key, i) (key, i) j = h (k, i) if T[j] == k return j i = i + 1 until T[j] == NIL or i = m return NIL Linear Probing index is computed using following hash function: h(k, i) = (h₁(k) + i) mod m h₁(k)= k mod m Quadratic probing index is computed using following hash function: h(k, i) = (h₁(k) + i²) mod m h₁(k)= k mod m Double hashing index is computed using following hash function: h(k, i) = (h₁(k) + i h₂(k)) mod m h₁(k)= k mod m h₂(k) = 1 + (k mod m - 1)
4. Using the Finite Galois Field, solve the operation of 01.89 Đ02.F1003.18 Đ01.4E (the given strings are in Hexadecimal). Give steps by steps details of your calculation. 5. Using the simplified RC4 Algorithm of 8 bytes (rather than the full 256 bytes), find the final Keystream and Cipherpext of the following Input string: S-Array of length 8, [SO S1 S2 S3 S4 S5 S6 S7] = [0 1 2 3 4 5 6 7] Key, K = [3 14 1 5] Plaintext, PT = [6 1 5 4] Hint: For the simplified stream generation, you can use this pseudocode (only up to the PT length): /* Initialization */ set i and j = o for i = i+ 1 to length of PT j = j + S[i] mod 8 [IS []s doms t = S[i] + S[j] mod 8 Keystream = end for
). This problem is about the chaining method we discussed in the class. Problem 3 (, Consider a hash table of size N = 11. Suppose that you insert the following sequence of keys to an initially empty hash table. Show, step by step, the content of the hash table. Sequence of keys to be inserted:
Please see attached
You are given a collection of N non-empty strings, denoted by S₁, S₂,..., Sn. Then you are given N-1 operations which you execute in the order they are given. The įth operation is has the following format: 'a b' (1-based indexing, without the quotes), which means that you have to make the following changes: 1. Sa = Sa+ Sb, i.e. concatenate ath string and 6th string and store the result in ath string, 2. S = "", i.e. make the 6th string empty, after doing the previous step. You are ensured that after the ith operation, there will be no future operation that will be accessing S. Given these operations to join strings, print the last string that will remain at the end of this process. Input The first line contains an integer N (1 ≤N≤ 105) denoting the number of strings given. Each of the next N lines contains a string denoting the S₁. All the characters in the string S, are lowercase alphabets from 'a' to 'z'. The total number of characters over all the strings is at most 106, i.e Σ₁|S₁|…
Suppose you have a hash table of size N = 64, and you are using pseudo-random probing. The keys in your hash are 4-digit integers (0000 through 9999) and your hash function is h(k) = (the sum of the digits in k). Assume that the first 4 slots of your pseudo-random probing array contain: 5, 10, 60, 30 What are the first 4 values in the probe sequence (starting with the home position) for a record with key k=1948?