What Is (Data Encryption Standard) DES Algorithm in Cryptography?

The ability to encrypt data is a crucial skill in cyber security. For a number of decades, the data encryption standard (DES) algorithm has been in use. Therefore, it makes sense to learn about its operation and application. We will talk about how the DES algorithm works and how it is used in this blog. Additionally, the triple DES algorithm will be discussed.

Let's take a look at the subjects that will be covered in this blog.

• What is DES Algorithm in Cryptography?
• DES Algorithm
• DES Algorithm Steps
• DES Algorithm Implementation
• Applications of DES Algorithm 

What is DES Algorithm in Cryptography?

The IBM team came up with the Data Encryption Standard Algorithm (DES) in the 1970s. The National Institute of Standards and Technology (NSIT) has since accepted it.

The DES encryption algorithm employs symmetric keys, which indicate that the data is encrypted and decrypted with the same key.

DES Algorithm

DES takes 64-bit plaintext as a input and create 64 bit ciphertext ( Using 64 bit per Block).The PT is divided into size of 64-bit block each and encrypted with 56 bit key at the initial level. At the decryption side, DES take 64-bit CT and creates 64 bit PT with 56 bit Key

DES depends on the two fundaments ascribes of cryptography

• Substitute

• Transposition

– DES consist of 16 steps, each of which is called as a round.

- Each round play out the means of substitution and transposition

-Block size is 64 bit

-No of Rounds 16

-Key Size is 64 bit

-The number of subkeys :16 

-Sub keys is 48 bit

-Cipher Text 64 bit

DES Algorithm Steps

1.64 bit PT block is handover to an Initial Permutation(IP) Function

2.The IP is performed on PT 

3.IP generated Left Plain Text (LPT) and Right Plain Text (RPT), the two sides of the permuted block.

4.16 rounds are required for both LPT and RPT Of encryption process.

5.In the end, LPT and RPT are rejoined and a Final permutation(FP) is performed on the combined block.

6.The result of this process produces 64-bit CT.

DES Algorithm Implementation

Initial Permutation :
– It happen only once (before the first round)
– Rearranging and Shuffling each bit (Transposition)
– This process is called jugglery of bit position
– After initial permutation the 64 bit PT block get divided into LPT and RPT

Rounds

Key Transformation:

-56 bit key is utilized during encryption

- 56 bit key is changed into 48 bit key

-Discarding every 8th bit of initial key, i.e. 8th , 16th ,32nd …..

-Each round generates a distinct 48 bit key from a 56 key, a process known as key transformation.

Expansion Permutation Process :

– We had two 32 bit LPT and RPT

– In step 2 RPT is expanded from 32 bit to 48 bit the process called as expansion permutation

– During this process bits are permuted as shown in next figure

– It is clear 32 bit of RPT get expanded with 48 bit which is XORed with 48 bit Key

– The resulting output of XOR operation is given to next step called as S-box substitution

S-Box Substitution :

- S-Box Substitution Process is accept 48 bit key and expanded RPT of 48 bit which get XORed and Produced 32 bit and produces 32 bit output

-The substitute is performed by eight Substitute Box called S-BOX

-S-box performs just jugglery(Substitute) on each bit positions and produces compressed bit

-The substitution performed using 8 substitution boxes the reason called as s-box.

P(Permuted)-BOX:
– 32 bit output from eight S-box is then permuted by P-Box
– So the Output of S-box is input of P-box
– Which 32 bits are permuted using straight forward permutation mechanism
– That means replacing each bit with a different bit in the specified table called as P-box permutation

XOR and Swapping:
– The output of P-box get XOR with the left plaintext ( 32-bit) produced New 32 bit RPT
– Output of XOR operation becomes new RPT and the old RPT becomes new LPT the complete process is called as XOR and Swapping.

Final Permutation

– Last operation is a permutation of 32 bit LPT and 32-bit RPT produced from XOR and Swapping process

– Final Permutation was performed after successful completion of 16 Rounds

– Inverse of Initial Permutation is also called as final permutation and This produces 64 bit Ciphertext

Applications of DES Algorithm 

When a weak encryption is required, the DES algorithm is used. It can be utilized in permutation generators as well as random number generators. The creation of triple DES legacy systems with three keys is one of the DES algorithm's most significant practical applications.