## Friday, March 5, 2010

### Encryption algorithm in cryptography

encryption algorithm is an algorithm that serves to make cryptography purposes. The algorithm must have the power to do (put forward by Shannon):

* Confusion, from the text so it is difficult to light reconstructed directly without using the decryption algorithm
* Diffusion / dissolution, from the text so that the characteristics of the bright light of the text is lost.

that can be used to secure information. In the implementation of a password algorithms must consider the quality of services / Quality of Service or QoS of the whole system which he implemented.

Basic underlying mathematical encryption and decryption process is the relation between the two sets of text that contains elements of light / that contains the plaintext and ciphertext elements. Encryption and decryption is a function of transformation between these sets. If the text elements are denoted by P light, the text elements are denoted with C code, is for the encryption process is denoted by E, decrypted with the notation D.

Encryption: E (P) = C

Decryption: D (C) = P or D (E (P)) = P

In general, based on common key, a password algorithm can be divided into:

* symmetric-key, often referred to as the conventional algorithm for passwords are generally applied to the classical password algorithm
* asymmetric-key

Based on the implementation and time era, can be divided into:

* Algorithms password :: classic cryptography
* Algorithm passwords :: modern cryptography

Based on the key secrecy can be divided into:

* Secret-key encryption algorithm secret-key
* Public-key encryption algorithm public-key

In symmetric-key scheme, used a same secret key for encryption and decryption process. While on-key system used asymmetric different key pair, commonly called the public key (public key) and private key (private key), used for encryption and decryption process. When the light of the text elements are encrypted using the private key element of the resulting ciphertext can only described using private key pair. And vice versa, if the private key used for encryption the decryption process must use the public key partner.

algorithms, symmetric key encryption

Algorithm scheme will be called the key password-symmetric if for any encryption or decryption process as a whole the data used the same key. This scheme is based on the amount of data per process and the flow of data processing in it are divided into two classes, namely, block-ciphers and stream ciphers.

Block-Cipher

Block-cipher algorithm is a password scheme that will divide the light text that will be sent with a certain size (called blocks) of length t, and each block is encrypted using the same key. In general, block-ciphers process plain-text in relatively long blocks of more than 64 bits, to make use of attack patterns that have to pick locks. To increase the reliability of this password algorithm model, also developed several types of encryption process, namely:

* ECB, Electronic Code Book
* CBC, Cipher Block Chaining
* OFB, Output Feed Back
* CFB, Cipher Feed Back

Stream-Cipher

Stream-cipher is the algorithm that encrypts the password data union data, such as bits, bytes, or per nible five bits (the data in the form of data encryption Boudout). Every single unit encrypts the data using a key that a key outcome of the generation before.
 Algorithm-key encryption algorithms, symmetric

Some examples of algorithms that use symmetric-key:

* DES - Data Encryption Standard
* Blowfish
* Twofish
* MARS
* IDEA
* 3DES - DES applied 3 times
* AES - Advanced Encryption Standard

This scheme is the algorithm that uses different keys for encryption and decryption. This scheme also known as public key cryptography system for encryption keys to be made to be known by the public (public-key) or can be known to anyone, but for the decryption process can only be done by the authorities who have to decrypt the secret key, called private-key . Analogy can be like a box that can only be opened by the postman who had the keys but anyone can enter letters into the box. The advantage of this model algorithm, to correspond confidentially with many secret key is not needed as there are parties, simply create two keys, namely the public key for the correspondent to encrypt the message, and the private key to decrypt the message. Unlike the symmetric key scheme, the number of keys is made of the number of parties to whom correspondence.