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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).
Encryption: Changing the Plain text to unreadable.
Decryption: 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. 

Eg:

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:

         euhdn

       

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.