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Issue 20.1 ('Debugging')
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Data Cryptography with the Feistel Network

More on Ciphers

Issue: 20.1 (January/February 2022)
Author: Eugene Dakin
Author Bio: Eugene works as a Senior Oilfield Technical Specialist. He has university degrees in the disciplines of Engineering, Chemistry, Biology, Business, and a Ph.D. in Chemical Engineering. He is the author of dozens of books on Xojo available on the xdevlibrary.com website.
Article Description: No description available.
Article Length (in bytes): 12,651
Starting Page Number: 32
Article Number: 20104
Resource File(s):

Download Icon project20104.zip Updated: 2022-01-02 19:45:20

Related Link(s): None

Excerpt of article text...

Horst Feistel was a German-Born physicist and he, along with Dan Coppersmith, worked on cryptography while working at IBM around 1974. The Feistel network is also called a Feistel cipher that is used to encrypt and decrypt data.

A quick explanation is that data is split into two pieces, and encryption occurs multiple times, which creates the encoded data. The number of iterations, and keys are different for each cipher that uses the Feistel network. Feistel Ciphers are used in two fish, padding schemes for certificates, key schedules, DES (Data Encryption Standard), and more.

There are exciting parts about Feistel Netwoks, such as the same algorithm that is used to encrypt data, is also the same algorithm to decrypt data. A Feistel Network is not really a cipher, it is actually the structure to build encryption algorithms, such as putting in the number of keys, length of keys, iterations, and then the Feistel network turns it into a cipher. The cipher (or algorithm) is then used to encrypt and decrypt data.

The general structure of the Feistel Network (Cipher) is shown in the diagram in Figure 1.

Let's work through the above figure to understand how this works by explaining each step, and this can be shown or proven in the attached Xojo program. Place the lower-case letter h in the Clear Text control, Key1 value of 1, with the Key2 value of 2.

Looking up the ASCII value of the letter h is 104 in decimal, which is the binary value of 01101000. The first step is to split the binary value in half, which creates a Left-side-step-1 value of 6 (L1), and a Right-side-step-1 value of 8 (R1).

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