Basics Of Cryptography

In this post I will teach you the basics of Cryptography.

Basic terminology

Encryption: Its an art, algorithm, process of changing/transforming your "Required Data" into other form called Cipher, explained below. So no one, except you or some Eligible person, cannot be able to identify. he will wonder, what's the meaning? or what is the use of  the given data?  Encryption is also known as Encoder or Encipher. It is done to secure the data from insecure channels.
 Example: when sender sends data to the to the receiver, this data reaches the receiver after passing through many insecure channels. So with the help of encryption we protect our data from being hacked.
* Required data can be any thing like Message, file, document, etc.


Decryption: Its the reverse of Encryption. It is the process of changing the Cipher into the understandable form, so that the proper meaning or proper use of the Data can be attained. Its output is the previous Data which was changed into the Cipher. Decryption is sometimes called as Dicipher or Decoder. Decryption is done mainly by the receiver to understand the actual text send by the sender.


Cryptography: When both the process, Encryption & Decryption, are combine the entire process is called Cryptography. Cryptography is seen as "Black Art" but of-course this is not the case. Its is mainly used as the science of communication.


Cipher: When you encrypt the Data using any encryption process, your data is converted into mysterious Data called cipher. Its meaning cannot be directly interpreted. To reveal the true meaning of the cipher we have to decrypt it. After Decryption the give cipher is converted into original or understandable form.


Uses of Cryptography:

Cryptography is mainly used as the "science of communication". Lets say a person . Say John, want to communicate with other person, say Sarah. But John want to communicate privately with the Sarah only. So what he can do is, he can encrypt his message and sends it to Sarah, if any-person in-between John and Sarah reads the message, he/ she does not know what is meaning.
Cryptography is also used to protect the Data which is present on the Disk or any other storage device. Cryptography is also used to Authenticate or to check the Message Integrity.
**Message Integrity : As the word 'message integrity' signifies, it checks the Integrity of the message, whether message sent or received was correct or not.

Types of Cryptography:

• Shared key cryptography
• Public key cryptography
• Modern Cryptography

Shared key Cryptography:

In Cryptography  key is used to encrypt or decrypt the data. When use the same/common key to encrypt or decrypt, it is called Shared key cryptography.
Example :
John want to send a message to Sarah saying " I love you " but at the same time he want only Sarah to understand the message. Now see what they have done is they agree made an algorithm write the message.
They shifted the all the alphabets of English by 4 alphabetically i.e.  A with D,  B with E, X with A, Z with C etc. So the message "I LOVE YOU " changed to " L  ORYH  BRX ". Now both the John and Sarah can read the message and understand but unwanted person cannot understand the message.
Note:  Key was same here. Shared key cryptography is also called as Symmetric key Cryptography.


Public Key Cryptography:

In this cryptography, different keys are use to encrypt and decrypt the data. As we have two keys , we have freedom here i.e. we can share our encryption key to anyone, means we can make it public, so that anyone can use this public key to encrypt the data. This is key is also called as public key.
But only the owner of the decryption key can decrypt the message. This key is called as private key.

Some Modern Cryptographic Algorithms:

Following are some modern cryptographic algorithms which are widely used in many domains like WEP, HTTP, SSL, etc.

• RC4 - symmetric algorithm
• RC2 - symmetric algorithm
• DES - symmetric algorithm
• 3DES - symmetric algorithm
• AES - symmetric algorithm
• RSA - public key algorithm

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