Case Study 5

 
 In computer science, a hash table or hash map is a data structure that uses a hash function to map identifying values, known as keys (e.g., a person's name), to their associated values (e.g., their telephone number).

• Secret Key Cryptography (SKC): Uses a single key for both encryption and decryption
• Public Key Cryptography (PKC): Uses one key for encryption and another for decryption
• Hash Functions: Uses a mathematical transformation to irreversibly "encrypt" information 

CASE STUDY 4

 1. What is hash collision?
In computer science, a hash collision is a situation that occurs when two distinct inputs into a hash function produce identical outputs.

 2. What really happens during a hash collision? Include an image

Hash tables may be used as in-memory data structures. Hash tables may also be adopted for use with persistent data structures; database indexes commonly use disk-based data structures based on hash tables.

3. What are the ways and methods to resolve hash collision? Explain Each

If keys are small integers, we can use an array to implement a symbol table, by interpreting the key as an array index so that we can store the value associated with key i in array position i. In this section, we consider hashing, an extension of this simple method that handles more complicated types of keys. We reference key-value pairs using arrays by doing arithmetic operations to transform keys into array indices.

reflection in case study 2

After reading the article, I would say even a country as  powerful as United  States  and more advanced devices and gadgets, there is still a chance  that hackers can penetrate their system. It is a warning that government unit should be  very careful in the terms  of security.
  
       Although the hacker said that he didn't deleted their system, there is still a possibility that anybody who able and will coupled can hack anyone's system .
     In general, we should be vi giant  in securing our PC and not gives out our personal information to everything..... that's all than you....

reflection in case study 1

For me,
From what I`v been reading the worm is a complicated one, the fact that it can open a door then get in and close it to prevent further access so i seems like nothings been tampered is pretty damn smart, it leaves no trace. I don't think someone would do all this for an elaborate hoax, the hoax is prolixly just covering what it will do. This does exist. It has been verified by Microsoft and numerous non-virus company people, so it does exist. The problem is that it was perhaps somebody's idea of an April Fools joke planned MONTHS ahead of time, in order to show how many idiots there are out there who hadn't patched their computers. I definitely agree  with the outcome the story.Even though  I am not a heavy users of PC ,it suggest everybody should use a strong password, update their anti-virus to prevent unidentified virus corrupting there system.  With all the advanced technology that are sprouting, came with growing in numbers of different viruses,as rule we should all be prepared  and careful in accepting and downloading defferent software. Now you know, you should be careful for everything....................

Reflection in the Prelim Topics

I learn about the linked list, stack, array and queues. I enjoy lessening in every discussion. i really like the subject/topic because its really challenging to us to students specially to ME!....

Application(examples)

LINKED LIST

•       Data structure composed of nodes, each node holding some information and a reference to another node in the list.

•      The main Applications of Linked Lists are
*In Symbol Table

Queues

Imagine you have a web-site which serves files to thousands of users. You cannot service all requests, you can only handle say 100 at once. A fair policy would be first-come-first serve: serve 100 at a time in order of arrival. A Queue would definitely be the most appropriate data structure.

 

Stack

Stacks help computers in unfolding their recursive jobs; used in converting an expression to its postfix form; used in Graphs to find their traversals (we have seen that); helps in non-recursive traversal of binary trees (we'll see this) and so on....

Arrays

Reflection: Arrays are useful mostly because the element indices can be computed at run time

example, an array of 10 integer variables, with indices 0 through 9, may be stored as 10 words at memory addresses 2000, 2004, 2008, … 2036, so that the element with index i has the address 2000 + 4 × i.^[4]