Introduction to Cryptography

Now a days Internet is important part of Life.  We are using Internet for sending confidential data also like password,for storing army secrets. But the Internet is insecure medium.  Do you know why?

Insecure Medium:
  Imagine you are sending a data.  In internet world data are separated as packets and send to destination.  Do you think the data directly reaching the destination?   If  you think so,you are wrong.  The packets are going through different routers.  Finally the data is send to user.  In this gap, Intruders(i mean attackers) takes advantages.  Intruders can see what you are sending.  Because your data are simple and easy to readable by anyone. 

How to secure the data?
    We can not stop the intruders and their activities.  But we can make our data as Unreadable for Intruders.  For this purpose the Cryptography is introduced.

Introduction to Cryptography:
     Julius Ceaser who introduce the Cryptography technology.  Cryptography is technology in which we are changing the plain text to unreadable text(known as cipher text) . 

In your home you put money in locker,  Isn’t it?  The locker probably has key to open.  Imagine  thief is coming to your home to steal.  if he want to open the locker,certainly he need the key.  Without the key he can not do. Yeah i can hear what you are saying, he can break the locker.  If the locker is very strong,he can not open it at all.

Likewise in cryptography also we are going to create a Key for our data.  So that Intruders can not read the data.  It is possible to read the data, if the encryption(will explain later) is weak.  So we need to encryption method very strong.

Terminologies used In cryptography:
   Plain Text:
               original data or text is known as Plain text.
   Cipher Text:
              The encrypted message(unreadable message).
             Changing the Plain text to unreadable.
            Changing the cipher text to plain text.

Traditional Encryption Methods:

  • Ceaser Cipher
  • Mono Alphabetic Cipher
  • Play Fair Cipher
  • Hill cipher
  • Poly Alphabetic Cipher
  • Rail Fence Technique.

Ceaser Cipher:
  Most simplest encryption method.  In this method we are going to replace the alphabets with shifted alphabets. 
Consider Plain text is:  break
if we use Key is 3, then the cipher text will be  found by:
        b+3 r+3 e+3 a+3 k+3
Shifted to three alphabets final cipher text is:


If the intruders see the cipher text(here “euhdn”) ,he can not understand anything.   But this method is easily hackable .  Because intruders can try 25 shifts and finally he can get the result. 
Many encryption methods are introduced to make better security.

Today  Encryption methods:

  •  AES(Advanced Entyption Standard)
  • DES(Data Encryption Standard)
  • RSA(Name of the creators).
  • MD5(Message Digest -5)
  • SHA(Secure Hash Algorithm

 For secure transaction , SSL (Secure Socket Layer ) is introduced.  In next post i’ll give detailed explanation for the SSL layer.