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Speaker

Prerita Agarwal

Data Specialist @

23 Jul, 2024 @ 01:30 PM

Introduction

Data Encryption Standard, abbreviated as DES, is a block cipher and a symmetric cipher, i.e., the same key is used for encryption and decryption.

The entire Data Encryption Standard procedure marks the input as a 64-bit plain text block and output as a 64-bit ciphertext. The key length of DES is 56 Bits.

The four steps for the Data Encryption standard are as follows:

Initial Permutation

16 Feistel Rounds

Swapping

Final Permutation(also known as inverse initial permutation)

Working of Data Encryption Standard

The same cycle works when there is a need to produce a 56-bit key.

Removal of every eighth bit

The specifications required for data encryption standard are as follows:

Additional Processes: Initial and Final Permutation

Round Function

Scheduled Key

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Initial and Final Permutation

Initial and Final Permutation works like the inverse of each other with the depiction of Permutation Boxes(also known as P- Boxes). They do not have any cryptographic significance in Data Encryption Standard.

Round Function

The entire performance of Data Encryption Standard as Cipher Feistel is based on the Round Function. The function signifies producing a 32-bit output with the application of a 48-bit key to the rightmost 32 bits.

1. Expansion Permutation Box: As the right input only consists of 32-bit and the round key consists of 48 bits, there is a need to expand the right input from 32 bits to 48 bits.The graphical representation of permutation logic in the Data Encryption Standard specification is below:

2. XOR: Data Encryption Standard performs XOR operation between the expanded right input and the round key. This is the only step that involves the usage of the round key.

3. S-Boxes: The S-Boxes deal with the real mess. Data Encryption Standard uses 8 S-Boxes, consisting of 6-Bit input and a 4-Bit output.

4. Straight Permutation: The 32-bit output obtained from the 8 S-boxes traverses through the straight permutation based on the following depiction:

Key Generation

The key generator produces 48-bit keys from 56-bit cipher key. The Data Encryption Standard includes Compression P-Box, Parity drop, and shifting logic.

Analysis of Data Encryption Standard

The Data Encryption Standard customizes the satisfaction of both the properties of the block cipher. The properties are described as

Complete Structure: Ciphertext consists of transforming many bits of plain text.

Avalanche Effect: Single change in plain text results in a drastic change in Cipher Text.

During the last few years, cryptanalysis has discovered some flaws in DES when the keys used are weak ones. These keys are should be avoided.

DES has proven to be an exceptionally well-designed block cypher. Except for an exhaustive key search, there have been no notable cryptanalytic attacks on DES.

Frequently Asked Questions

How many iterations are there in DES Algorithm?

There are 16 iterations in Data Encryption Standard Algorithm.

What is the key length of the Data Encryption Standard Algorithm?

The key length of the Data Encryption Algorithm is 64 Bits.

What is the size of the initial permutation matrix?

The size of the initial permutation matrix is 8*8.

What is the size of the round key in the DES algorithm?

The size of the round key in the DES algorithm is 48 bits.

What is the size of round input in the DES algorithm?

The size of round input in the DES algorithm is 32 bits.

Conclusion

Congratulations on finishing the blog!! After reading this blog, you will grasp the concept of the Data Encryption Standard.