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Now a days a security is necessary for the any application.Taking an example of india-pakistan.The war is not going only at physical side but also the digital(cyber side).Pakistani hackers are hacking indian websites and indian hackers are hacking paskitani websites.So the security is necessary.

Generally Encryption algorithms are used for the security purpose.Generally these are divided into to parts.

A.Symentic key encryption :- in this encryption the key which is used to encrypt the data is same for the sender and the receiver.

B.Public key encryption :- in this the key which is going to be used for the encryption algorithm is different for the sender and the receiver.It is based on the public key and private key.

There are lots of techniques of encryption algorithms.Several techniques i am showing here.

(1) Steam Ciphering and block ciphering :- It looks at the input palintext(data | information )as a stream of bits and encrypts them one bit(or byte) at a time as the steam progresses.In this technique, the length of the Plaintext and the key size will be same.Wireless LAN uses steam Cipher

In block cipher ,one whole block of plaintext is take to produce the ciphertext block(encrypted block) of equal length.Block may be of 64 bits or the 128 bits.

(2) Symmetric Key Cryptography :- Here the same key is used for the both side of encryption and the decryption.It is like a lock where the same key is used for it to lock and the unlock it.It is called also convential classical algorithms.

In this cryptography there are four components.

1.Plaintext

2.Encryption/Decryption algorithms

3.Secret Key

4.Cipher Text(Encrypted Text)

Where c1 c2 are the cipher text p1 p2 are the plain text Ek is the encryption algorithms where k defiens the Key.and same as Dk is the decryption algorithms where K defines the key.

Here in 1st phase if the cipher text is generated then it is the key for the next plaintext to produe the new cipher text.same as in decryption.

This algorithms have many types some of are here.

1. DES – Data encryption standard,this algorithm is the most widely used,researched a lot time and implemented new things day by day.

2. 3DES - Here on plain text the DES algorythm is implemented 3 times to make that Plaintext more encrypted for the security incesement.

3. AES – Advance Encryption Standards,This is the current accepted standard for the encryption by FIPS(Fedaral Information Processing Standard) Of USA.

4. Skipjack/FORTEZZA :- This is the token – based symentric algorithm used by defence personnel in US.

(3) DES (Data Encryption Standard) :- It employees the principle of scrambling and substitution.This process are repeated the numbers of times with keys to ensure that the palintext is completely transofrmed into a throughlt scrambled bit stream.

Working of DES :-

3DES(Tripple DES) :- It uses the same DES algoritm 3 times in succession with different keys.This incereses the keysize resulting in higher security.There are 2 different flavour of 3DES.One uses two 56 – bit key and the other uses three 56 – bits keyy.By using three 56 – bits key,the effective security can be incresed to the key size,to 168 bits.3DES is used widely in the world now a days for the reason of the security purpose.

(4) AES (Advance Encryption Standard) :- DES algorithm widely used over the world.But after starting the use they come to know that this encryption algorithm have some drwabacks.so to overcome the drwabacks AES came.AES had to be a symmetric cipher with block size of 128 bits.it supports the key of 128- bits,192bits and 256 bits.

Characteristics of AES :-

1.Design Simplicity.

2.Resistance against all famous known attacks.

3.Wide range of platforms.

4.Speed and coe compactness.

In Each Block the operation works as per shown in the below figure.

(5) Public Key Cryptography :- Here is not like symetric key encrtption.Here at the both side the key is defferent which is going to be used for the encryption and the decryption.These encryption and the decryption keys are the key of 1 pairs.one of these keys from the key pair is made public and another one kept private or the secret.

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- frogmode620
- New User
**Posts:**6**Joined:**Wed Sep 19, 2012 3:43 am**Blog:**View Blog (0)

Nice. However, I think stream and block ciphers might need to be clarified: Block ciphers is just taking a key, and using it over and over on a piece of text. Stream ciphers is just randomly generating a key that's as long as the text, but it has a drawback as you need to give that huge key to the recipient.

- not_essence2
- Poster
**Posts:**189**Joined:**Fri Sep 14, 2012 6:09 pm**Blog:**View Blog (0)

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