Cooper_Assignment #4

Encryption methods, such as the Caesar Cipher encryption, allow us to encrypt and decrypt text using a special key. Another method of encrypting text / passwords is called hashing. Hashing uses special algorithms to 'scramble' the text, which is tougher to be hacked. The hash function can take numbers, letters, and symbols as input, then the function applies one of the special algorithms to output the scrambled text. The longer the output string is, the harder to hack the hashed data. The difference between hashing and the Caesar Cipher encryption is that one cannot 'decrypt' a hashed data to its original text. Since a hashed data cannot be decrypted, a user must enter the original text, which will be hashed by the program. Then the program compares the hashed value with the hashed data stored previously for the original text. A salt is used, at times, to create a random sequence that is added to the original text before using the hashing algorithm. This can help prevent the Brute…

The hash function h(k)= [(m(kA mod 1)] for A = 2-³ is used to insert the keys 61, 62, 63, 64, and 65 into a hash table of size m = 1000. The order of the hash codes in the table are given by a. 625, 125, 0, 750, 875 b. 625, 750, 625, 125, 0 c. 625,125, 0, 875, 750 d. 625, 750, 875, 0, 125 e. 625, 750, 125, 875, 0

a) An example of the linear hash index is given below. Every time a new overflow page is added, the bucket pointed by Next is split, and Next is incremented by one. Show the index state after adding the keys 39, 25, and 29. hi ho Level=0, N=4 000 00 0*8* 001 01 17*33* 010 10 6*26* 42* 011 11 7* 11* 15* 23* 100 00 4* 12* 20* 101 01 5* 13* 21* 37* Next

cryptography in hash function

Computer Science Within a Java class, write a method that creates n random strings of length 10 and inserts them in a hash table. The method should compute the average time for each insertion. provide code and output.

A hash function H accepts a variable length block of data (plaintext) as input and produces a fixed size hash value ix xi. a. H(N) b. H(P) c. M(H) d. H(M)

Given a hash table of size 8, and the hash table uses haah() +i+ in the i-th probe for collsion resolution, what are the indexes of the following elements in the table if the elements are inserted into the table in the following order: String hashCode 79 111 81 "W 87 66 7. "g 2

1. An open hashing scheme requires the use of random access ( true /false ). 2. A good hashing function should ___ distribute the records amongthe buckets. 3. For an open hashing scheme with 100 buckets and 4000 records,the average number of record reads to locate a record is equal to___.

The hash table array has capacity of 10. Capacity is the number of slots present in the array that is used to build the hashtable. The hash function returns the absolute value of the key mod the capacity of the hash table. a) Insert these keys in the hash table: 3,23,11,21,1,7,77,8 where the hash table uses quadratic probing to resolve collisions. b) Search and Delete 3 and 11 from the table. Be careful about changing the status of the table slot to “deleted” after deleting each item. c)Search 23 and 21 from the table and print their position.

Question # 1: Use the Multiplicative Cipher method to encrypt the following plaintext:We will succeed in our ventureKey length K = 7 You must show all the steps of your workQuestion # 2: Use the additive cipher with key = 15 to decrypt the message “WTAAD”.You must show all the steps of your work Question # 3: Use the concept of a one-way hash function to encrypt the following name into a 9 x 9 -dimensional database table. Jonathan Leea) How many rows and columns are there on this tableb) Which indices is Jonathan on this tablec) Why are hash functions relevant in database encryption?d) What would you do to remedy the problem of index congestion on your database?You must show all the steps of your work Question # 4: Use the multiplicative method to decrypt the following ciphertext.MADWU Key = 5You must show all the steps of your workQuestion # 5: use the XOR technique to encrypt the following statement before transmission: The quick brown fox jumps over the lazy dog

4 A hash code is generated by the Java hash algorithm for Strings based on a string's highest allowed character count. Explain how a powerful, constant-time hashing method can be created given that Strings have no useful maximum length. Which eight letters, say, would you select to symbolize a string of length l if you had to?

Which of these is NOT a characteristic of a secure hash algorithm? a. Collisions should be rare. b. A message cannot be produced from a predefined hash. c. The results of a hash function should not be reversed. d. The hash should always be the same fixed size.

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A hash code is generated by the Java hash function for Strings based on a string's highest allowed character count. Explain how a powerful, constant-time hashing algorithm can be created given that Strings have no useful maximum length. Which eight characters, say, would you select to represent a string of length l if you had to?

hash table

A message is made of 10 numbers between 00 and 99. A hash algorithm creates a digest out of this message by adding all numbers modulo 100. The resulting digest is a number between 00 and 99. Does this algorithm meet the first criterion of a hash algorithm? Does it meet the second criterion? Does it meet the third criterion?

Assume a hash table utilizes an array of 13 elements and that collisions are handled by separate chaining. Considering the hash function is defined as: h(k)=k mod 13. i) Draw the contents of the table after inserting elements with the following keys: 36, 243, 261, 180, 217, 180, 21, 16, 182, 202, 91, 97, 166, 78, 33, 70, 51, 58.

A hash table is a very important data structure in computer science. It is used for fast information retrieval. Itstores data as a < key, value > pair, where the value is indexed by the key. Note that keys must ne unique.Consider the example of storing persons name using the social security number (ssn) as the key. For eachssn x, a hash function h is used, where h(x) is the location to store the name of x. Once we have created atable, to look up the name for ssn x, we can recomputes h(x) and then look up what is stored in that location.In Python, dictionaries are based on hash tables. Typically, the hash function h is deterministic; we do notwant to get different results every time we compute h(x). But h is often chosen to be pseudo-random. Forthis problem, we will assume that h is truly random. Suppose there are k people, with each person’s namestored in a random location (independently), represented by an integer between 1 and n, k < n. It mayhappen that one location has…

Using the modulus operator within a hash function or on the output of a hash function: Will always cause rehashing. Will cause the hash table to shrink. Can cause collisions. O Will always produce a unique hash bucket.

Q4:Let be a hash function whose input is a string of bits of arbitrary size and the output is a string of m bits. Explain why the security of this function is m/2.

A hash function should be independent of the capacity of the hash table. Select one: a. False O b. True

A typical hash function often consists of the following three steps: Group of answer choices hashing, compressing, and indexing. multiplication, addition, and modularization. selecting, digitizing, and combining. modularization, probing, and indexing. compressing, hashing, and probing.

3. Cuckoo hashing. Consider a cuckoo hash table for six items, with two tables of size 5 (similar to what we have in the textbook example). Use the following hash functions to insert items in the order of U, V, W, X, Y, Z. Be sure to include some steps so that the instructor can trace your work.

3. Given the following keys: 68, 39, 89, 28, 79 Take alpha = 0.6 Compute m (size of hash table), and select it to be a prime number. Now illustrate how you would construct the hash table. Use double hashing as collision resolving technique. The original hash function, is h(k)= k mod m The second hash function for double hashing, h₂(k)=8-(k mod 8)

Draw the contents of the hash table given the following conditions: The size of the hash table is 25. • Linear Probing is used to resolve collisions. • The hash function H(k) should be calculated in the following way where k is the element to be hashed: R(k) = k mod (summation of last two digits of your student id + 7) If R(k)<10 H(k)=R(k) + 8 else H(k)=R(k) - 4 What values will be in the hash table after the following sequence of insertions? 55, 65, 8, 18, 20, 11, 56, 27, 15, 167 [Note: Draw the values using a hash table and show your work for partial credit.]

Exercise 2 - Hashing a String 2 Apply your hash function to anagrams, e.g., cat, tac Will they be given the same hash value? • How can we remedy this? We could use the position of the character as a weight. 1 position 2 3 a 99*1 +97*2 + 116*3 = 641 641 % 11 3

2-A linear probing hash table of length 10 uses the hash function h(x) = x mod 10 + 1. mod is the reminder opertatro. For example the h(42) = 42 mod 10 + 1 = 2 + 1 = 3 so we insert 42 in t he position 3 in the array. After inserting 6 integer keys into an initially empty hash table, the array of keys is 1 2 3 4 5 7 8 9. 42 23 34 52 46 33 a- insert the key 35 b- insert the key 12 c- insert the key 10

Write a complete C program using hashing : Prompt the user to search for the student id by the student's name

All of these statements are related to hash function, hash table.