Security Concepts

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Encryption:
 It is the process of converting message (referred as plain text in cryptography) into another form (referred to as cipher text) in such a way that only authorized persons can read or understand it.So, it is nothing but converting plain text to cipher text .This is done by some encryption algorithms .And decryption is the reverse operation,takes cipher text and converts back to the plain text.


The input to the encryption algorithm is the key.The key can be anything,it can be a simple word,number, or some series of random letters.

Symmetric Key Algorithms:
    In symmetric key algorithm single key is used for both performing encryption and decryption.So,the other node that wants to communicate should have this key.For this operation there are key exchange protocols.

Eg: RC4,3DES etc

Asymmetric Key Algorithms:
     In asymmetric key algorithms,there are two keys:public key and private key.Public key is shared and private key is secret.In order to encrypt we use public key and it is decrypted by using private key.
Eg: RSA

Cipher:
 Algorithm used to perform encryption or decryption is called cipher.There are two types of ciphers:
1.Stream Cipher 2.Block Cipher

Stream Cipher:
   Encryption is performed bit by bit.

Block Cipher:
  Encryption is performed block by block. The length of the block varies,it can be 128 bits or 256 bits.

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