netwinz
DATA ENCRYPTION STANDARD (DES)
Introduction:
The Data Encryption Standard (DES) is a block cipher that uses shared secret encryption. It was selected by the National Bureau of Standards as an official Federal Information Processing Standard (FIPS) for the United States in 1976 and which has subsequently enjoyed widespread use internationally. It is based on a symmetric-key algorithm that uses a 56-bit key. The algorithm was initially controversial because of classified design elements, a relatively short key length, and suspicions about a National Security Agency (NSA) backdoor. DES consequently came under intense academic scrutiny which motivated the modern understanding of block ciphers and their cryptanalysis.
DES is the archetypal block cipher — an algorithm that takes a fixed-length string of plaintext bits and transforms it through a series of complicated operations into another cipher text bit string of the same length. In the case of DES, the block size is 64 bits. DES also uses a key to customize the transformation, so that decryption can supposedly only be performed by those who know the particular key used to encrypt. The key ostensibly consists of 64 bits; however, only 56 of these are actually used by the algorithm. Eight bits are used solely for checking parity, and are thereafter discarded. Hence the effective key length is 56 bits, and it is never quoted as such. Every 8th bit of the selected key is discarded, that is, positions 8, 16, 24, 32, 40, 48, 56, 64 are removed from the 64 bit key leaving behind only the 56 bit key.
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HOW TO CONDUCT THE EXPERIMENT:
TRANSMITTER:
1. Click on Presentation Layer on the Main Window and Then Select "DES " Module from the Modules displayed in the centre of the window.
DES CIPHER Window will open up as shown in SNAPSHOT-1.
SNAPSHOT-1
2. Enter the "IP Address" of the computer to which you intend to send data.
3. Enter the Key for Encryption. The key has to be 8 characters.
4. Enter the Data that needs to be encrypted in the "TEXT" textbox.
5. Click on "ENCRYPT" button to encrypt the data and display the encrypted data in the table.
The table displays the Block of Encryption, Original Character and the encrypted code as shown in SNAPSHOT-2.
Look how padding is applied at the end of the table if data is not modulo 8.
6. Click on the "SEND" button to send the encrypted data to the destination IP.
SNAPSHOT-2
Use Loop back Address "127.0.0.1" to send the Frame to the same computer.
At this point you can notice that you cannot send another frame until ack is sent from the receiver.
RECEIVER:
In the Receiver Window, the Frame is displayed in the table as soon as the frame is received. The Error Frames whose CRC does not match is marked in red as shown in SNAPSHOT-3.
1. Key in the Error Frame Number in the textbox provided for the Sequence Number and click "SEND REJ" to send rejection.
2. The Transmitter now transmits the correct frame and is reflected in the receiver table.(The Red color changes to white)
3. Send rejection for all the error frames by following the previous step.
4. Once all the frames are received correctly, click On "SEND ACK ALL" button to acknowledge all the 8 frames.
At this point, frames 1 to 8 on transmitter is enabled again and you can send another window of frames.
SNAPSHOT-3
Transmitter and Receiver Messages are displayed in the "Message Window" on the extreme right.
Click On "RESET" button to reset all the controls to initial values.
Click on "HELP" button to open this Manual.
Click on "EXIT" button to close this Window.
Copyright © 2011 Emblitz Technologies Pvt Ltd. All rights reserved. www.netwinz.com
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A Brief Overview of Cryptographyby YourPartofEVIL3,713 views
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btcooper11 1 week ago
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ClairElsedc672 2 months ago
@jainarpitha7
sorry was all in description
shazlitahir 4 months ago
@jainarpitha7
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shazlitahir 4 months ago