What is Symmetric Key Encryption

Symmetric Key Encryption is one of Cryptographic Tools use for secret communication , some times called conventional encryption or single-key encryption .

This diagram explain algorithm :

We have in diagram 5 things , plaintext , encryption algorithm , secret key , decryption algorithm , and ciphertext .

How algorithm run ?

Plaintext : Our message we need to transfer to another side , it's our in put that fed into encryption algorithm .

Encryption Algorithm :It's do some substitutions and transformations on the plaintext , to encrypting plaintext by using secret key information .

Secret key :It's have information that need to encryption and decryption .

Decryption Algorithm : We can say reverse of encryption , take ciphertext and by using secret key to decryption message to original plaintext .

Ciphertext : scrambled message encrypted by encryption algorithm using secret key information and transfer to other side , it will be input to decryption algorithm , and by using secret key will be original plaintext .

To make this symmetric strong we need tow things :
first : strong algorithm , to encrypting message .
second : secret key must keep secure .

Tow way to Attacking Symmetric Encryption :
1- cryptanalysis , to use it we need some knowledge of the general characteristics of the plaintext .
2- brute-force attack , we try all possible keys until plaintext is obtained .

Sources: Computer Security: Principles and Practice by William Stallings and Lawrie Brown .

more... Résuméabuiyad

What is Text ?

Text  is  obviously  the  simplest  of  data  types  and  requires  the  least  amount  of  storage.

Text in the form of words, sentences, and paragraphs is used to communicate thoughts, ideas, and facts in daily life.

Text  may  not  be  as  visually  exciting  as  some  of  the  other  media  types,  but  it  often  conveys  essential  and  precise  information.

Text elements

Alphabet characters

    A – Z and a – z 

Numbers

    0 – 9 

Special characters

    Punctuation (. ,  ; “ ‘ ! : -  /)

    Signs ($ + - = @ # % ^ & *)

Obtaining Text

Text can be captured in following ways:

• Keyboard
• Mouse
• Scanner (OCR) – Optical Character Recognition ((designed to translate images of handwritten or typewritten text (usually captured by a scanner) into machine-editable text ))

Types of Text

Unformatted text (Plaintext)

comprise strings of fixed-sized characters from a limited character set. 

Formatted text (Richtext)

comprise strings of characters of different styles, size and shape together with tables, graphics and image inserted at appropriate point.

Example: Rich Text Format (RTF), HTML, .doc

Hypertext

It enables the integrated set of documents (each comprising formatted text) to be created which have defined linkages between them.

more... Résuméabuiyad

What is an Operating System?

Operating System is :
A program that acts as an intermediary between a user of a computer and the computer hardware.

Operating system goals:

• Execute user programs and make solving user problems easier.
• Make the computer system convenient to use.
• Use the computer hardware in an efficient manner.

Some definition of operating system :

* OS is a resource allocator
    Manages all resources
    Decides between conflicting requests for efficient and fair resource use

* OS is a control program
    Controls execution of programs to prevent errors and improper use of the computer

* No universally accepted definition

* “Everything a vendor ships when you order an operating system”is good approximation
      But varies wildly

* “The one program running at all times on the computer”is the kernel. Everything else is either a system program (ships with the operating system) or an application program

more... Résuméabuiyad

What is multimedia?

Multimedia  

The  word  multimedia  is  composed  of  two  parts:  the  prefix  multi  and  media.
Multi = Plural, more than 1, many
Media = Medium of communication

Definition:
Multimedia is the presentation of a computer application incorporating media elements such as text, graphics, animations, audio, and video.

Classification of media types

Classification of media types

Characteristics of Multimedia System

They  must  be  computer-controlled. User is able to view, hear, and see using a Multimedia PC System.

They  are  integrated. At least one discrete and one continuous media combined for information presentation and sharing.

The information  they  handle  must  be  represented digitally.

The  interface  to  the  final  user may  permit  interactivity. User is able to navigate, interact, create, and communicate.

Benefits of using multimedia in software

* Ease of use

        User friendly, increase user’s effectiveness

*Intuitive Interface

        Allows user to determine functions of an application by their own intuition

*Immersive Experience

         Software application takes over the entire computer screen, allows user to focus on application 

*Self-paced interaction & better retention

         allows information processing at one’s own pace.

*Better understanding

         simultaneous presentation of different media provides richer & broader range of information.

*Cost effectiveness

          less training, less technical support

Problems with Multimedia 

Investment costs

- multimedia involves high volume of content

- expensive copyright and royalty

Technical barriers (accessibility issues)

- upgrade IT & PC infrastructure

Legal problems 

        - Copyright

Where to use multimedia ?

• Business
• Government
• Education
• Broadcasting & Entertainment
• Research & Development
• Health

more... Résuméabuiyad

What are Viruses ?

Viruses 

Viruses is piece of software that infects programs include:

• modifies them to include a copy of the virus
• replicates and goes on to infect other content
• easily spread through network environments

when attached to an executable program a virus can do anything that the program is permitted to do like:

• executes secretly when the host program is run

Virus Components :

infection mechanism

means by which a virus spreads or propagates

also referred to as the infection vector

trigger

event or condition that determines when the payload is activated or delivered

sometimes known as a logic bomb

payload

what the virus does (besides spreading)

may involve damage or benign but noticeable activity

Virus Phases

dormant phase

virus is idle

will eventually be activated by some event

not all viruses have this stage

triggering phase

virus is activated to perform the function for which it was intended

can be caused by a variety of system events

propagation phase

virus places a copy of itself into other programs or into certain system areas on the disk

may not be identical to the propagating version

each infected program will now contain a clone of the virus which will itself enter a propagation phase

execution phase

function is performed

may be harmless or damaging

Virus Classifications

we can classification virus by target or by strategy

1-classification by target

boot sector infector

infects a master boot record or boot record and spreads when a system is booted from the disk  containing the virus

file infector 

infects files that the operating system or shell considers to be executable

macro virus

infects files with macro or scripting code that is interpreted by an application

multipartite virus

infects files in multiple ways

2-classification by concealment strategy

encrypted virus

a portion of the virus creates a random encryption key and encrypts the remainder of the virus

stealth virus

a form of virus explicitly designed to hide itself from detection by anti-virus software

polymorphic virus

a virus that mutates with every infection

metamorphic virus

a virus that mutates and rewrites itself completely at each iteration and may change behavior as well as appearance

.........................................................

follow us in facebook and twitter:

facebook- twitter

more... Résuméabuiyad