ENCRYPTION AND DECRYPTION
ALGORITHM
Encryption is a process of coding information which
could either be a file or mail message in into cipher text a form unreadable
without a decoding key in order to prevent anyone except the intended recipient
from reading that data. Decryption is the reverse process of converting encoded
data to its original un-encoded form, plaintext.
A key in cryptography is a long sequence of bits used by
encryption / decryption algorithms. For example, the following represents a
hypothetical 40-bit key:
00001010 01101001
10011110 00011100 01010101
When a user encodes a file, another user cannot decode and read the file without the decryption key. Adding a digital signature, a form of personal authentication, ensures the integrity of the original message
“To encode plaintext, an encryption key is used to impose an encryption algorithm onto the data. To decode cipher, a user must possess the appropriate decryption key. A decryption key consists of a random string of numbers, from 40 through 2,000 bits in length. The key imposes a decryption algorithm onto the data. This decryption algorithm reverses the encryption algorithm, returning the data to plaintext. The longer the encryption key is, the more difficult it is to decode. For a 40-bit encryption key, over one trillion possible decryption keys exist.
There are two primary approaches to encryption: symmetric and public-key. Symmetric encryption is the most common type of encryption and uses the same key for encoding and decoding data. This key is known as a session key. Public-key encryption uses two different keys, a public key and a private key. One key encodes the message and the other decodes it. The public key is widely distributed while the private key is secret.
Aside from key length and encryption approach, other factors and variables impact the success of a cryptographic system. For example, different cipher modes, in coordination with initialization vectors and salt values, can be used to modify the encryption method. Cipher modes define the method in which data is encrypted. The stream cipher mode encodes data one bit at a time. The block cipher mode encodes data one block at a time. Although block cipher tends to execute more slowly than stream cipher, block”
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BACKGROUND OF ENCRYPTION AND DECRYPTION ALGORITHM
CRYPTOGRAPHY is an algorithmic process of converting a plain text or clear text message to a cipher text or cipher message based on an algorithm that both the sender and receiver know, so that the cipher text message can be returned to its original, plain text form. In its cipher form, a message cannot be read by anyone but the intended receiver. The act of converting a plain text message to its cipher text form is called enciphering. Reversing that act (i.e., cipher text form to plain text message) is deciphering. Enciphering and deciphering are more commonly referred to as encryption and decryption, respectively.
There are a number of algorithms for performing encryption and decryption, but comparatively few such algorithms have stood the test of time. The most successful algorithms use a key. A key is simply a parameter to the algorithm that allows the encryption and decryption process to occur. There are many modern key-based cryptographic techniques . These are divided into two classes: symmetric and asymmetric (also called public/private) key cryptography. In symmetric key cryptography, the same key is used for both encryption and decryption. In asymmetric key cryptography, one key is used for encryption and another, mathematically related key, is used for decryption.
There are several ways of
classifying cryptographic algorithms. For purposes of this report they will be
categorized based on the number of keys that are employed for encryption and
decryption, and further defined by their application and use. The following are
the three types of Algorithm that are disscused
·
Secret Key Cryptography (SKC): Uses a single
key for both encryption and decryption
·
Public Key Cryptography (PKC): Uses one key for
encryption and another for decryption
·
Hash Functions: Uses a mathematical
transformation to irreversibly "encrypt" information
refference :
http://homepages.uel.ac.uk/u0430614/Encryption%20index.htm