03-08-2012, 02:43 PM
Data Encryption and Decryption
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ABSTRACT
In the present system the network helps a particular organization to share the data by using external devices. The external devices are used to carry the data. The existing system cannot provide security, which allows an unauthorized user to access the secret files. It also cannot share a single costly printer. Many interrupts may occur with in the system. In this project the networking allows a company to share files or data without using some external devices to carry the data. Similarly a company can share the single costly printer. Though it is advantageous we have numerous disadvantages, somebody writes the program and can make the costly printer to misprint the data. Similarly some unauthorized user may get access over the network and may perform any illegal functions like deleting some of the sensitive information like employee salary details while they are in transactions.
. INTRODUCTION
The project “Data Encryption and Decryption” is totally enhanced with the features that enable us to feel the real-time environment. Today’s world is mostly employing the latest networking techniques instead of using stand-alone PC’s. Encryption or information scrambling, technology is an important security tool. Properly applied it can provide a secure communication channel even when the underlying system and network infrastructure is not secure. This is particularly important when data passes through shared systems or network segments where multiple people may have access to the information. In these situations, sensitive data and especially passwords should be encrypted in order to protect it from unintended disclosure or modification. Encryption is a procedure that involves a mathematical transformation of information into scrambled gobbledygook, called “cipher text”. The computational process (an algorithm) uses a key, actually just a big number associated with a password or pass phrase to compute or convert plain text into cipher text with numbers or strings of characters. The resulting encrypted text is decipherable only by the holder of the corresponding key. This deciphering process is also called decryption.
CRYPTOGRAPHY:
Cryptography is the science of writing in secret code and is an ancient art; the first documented use of cryptography in writing dates back to circa 1900 B.C cryptography came soon after the widespread development of computer communications. In data and telecommunications, cryptography is necessary when communicating over any untrusted medium, which includes just about any network, particularly the Internet.
ENCRYPTION:
Encryption refers to algorithmic schemes that encode plain text into non-readable form or cipher text, providing privacy. The receiver of the encrypted text uses a “key” to decrypt the message, returning it to its original plain text form. The key is the trigger mechanism to the algorithm.
Until the advent of the Internet, encryption was rarely used by the public, but was largely a military tool. Today, with online marketing, banking, healthcare and other services, even the average householder is aware of encryption.
Web browsers will encrypt text automatically when connected to a secure server, evidenced by an address beginning with https. The server decrypts the text upon its arrival, but as the information travels between computers, interception of the transmission will not be fruitful to anyone “listening in.” They would only see unreadable data. There are many types of encryption and not all of it is reliable. The same computer power that yields strong encryption can be used to break weak encryption schemes.
DATA ENCRYPTION STANDARD
The most widely used encryption scheme is based on Data Encryption Standard (DES) adapted in 1977 by the National Bureau of Standards, now National Institute of Standards and Technology (NIST), as Federal Information processing standard 46 (FIPS PUB 46). The algorithm itself is referred to as the Data Encryption Algorithm (DEA). For DES, data are encrypted in 64-bit blocks using a 56-bit key. The algorithm transforms 64-bit input in a series of steps into a 64-bit output. The same steps, with the same key, are used to reverse the encryption.
DES ENCRYPTION
The overall scheme for DES encryption is illustrated in Figure below. As with any encryption scheme, there are two inputs to the encryption function: the plain text to be encrypted and the key. In this case, the plain text must be 64 bits in length and the key is 56 bits in length.
Looking at the left hand side of the figure, we can see the processing of the plain text proceeds in three phases. First, the 64-bit plain text passes through an initial permutation (IP) that rearranges the bits to produce the permuted input. This is followed by a phase consisting of 16 rounds of the same function, which involves both permutation and substitution functions. The output of the last (sixteen) round consists of 64 bits that are a function of the input plain text and the key. The left and right halves of the output are swapped to produce the pre-output. Finally, the pre-output is passed through a permutation (IP-1) that is the inverse of the initial permutation function, to produce the 64-bit cipher text. With the exception of the initial and final permutations, DES has the exact structure of Feistel cipher, as shown in the figure.