What Is DES (Data Encryption Standard)? DES Algorithm and Operation [Updated]

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We live so much of our lives today on the internet. Whether it’s for storing our personal information, finding entertainment, making purchases, or doing our jobs, our society relies increasingly on an online presence. Cassava Starch Dough Making Machine

This increased dependence on the internet means that information security is more important than ever. The stakes are too high now. Users need to know that their sensitive data is kept confidential, unmodified, and readily available to authorized readers.

Data encryption is just one weapon in the cybersecurity arsenal, but it’s one of the oldest and most used. And since no discussion about data encryption is complete without talking about DES, here we are!Become an Expert in the Cyber Security FieldPost Graduate Program In Cyber Security Explore Program

DES stands for Data Encryption Standard. There are certain machines that can be used to crack the DES algorithm. The DES algorithm uses a key of 56-bit size. Using this key, the DES takes a block of 64-bit plain text as input and generates a block of 64-bit cipher text.

The DES process has several steps involved in it, where each step is called a round. Depending upon the size of the key being used, the number of rounds varies. For example, a 128-bit key requires 10 rounds, a 192-bit key requires 12 rounds, and so on.

Take a look at the video below which explains steps for encryption and decryption in detail, future of the Data Encryption Standard in cryptography and live example to further highlight the characteristics of DES encryption.

The DES (Data Encryption Standard) algorithm is a symmetric-key block cipher created in the early 1970s by an IBM team and adopted by the National Institute of Standards and Technology (NIST). The algorithm takes the plain text in 64-bit blocks and converts them into ciphertext using 48-bit keys.

Since it’s a symmetric-key algorithm, it employs the same key in both encrypting and decrypting the data. If it were an asymmetrical algorithm, it would use different keys for encryption and decryption.

DES is based on the Feistel block cipher, called LUCIFER, developed in 1971 by IBM cryptography researcher Horst Feistel. DES uses 16 rounds of the Feistel structure, using a different key for each round.

DES became the approved federal encryption standard in November 1976 and was subsequently reaffirmed as the standard in 1983, 1988, and 1999.

DES’s dominance came to an end in 2002, when the Advanced Encryption Standard (AES) replaced the DES encryption algorithm as the accepted standard, following a public competition to find a replacement. The NIST officially withdrew FIPS 46-3 (the 1999 reaffirmation) in May 2005, although Triple DES (3DES), remains approved for sensitive government information through 2030.

The plain text is divided into smaller chunks of 64-bit size. The IP is performed before the first round. This phase describes the implementation of the transposition process. For example, the 58th bit replaces the first bit, the 50th bit replaces the second bit, and so on. The resultant 64-bit text is split into two equal halves of 32-bit each called Left Plain Text (LPT) and Right Plain Text (RPT).

We already know that the DES process uses a 56-bit key, which is obtained by eliminating all the bits present in every 8th position in a 64-bit key. In this step, a 48-bit key is generated. The 56-bit key is split into two equal halves and depending upon the number of rounds the bits are shifted to the left in a circular fashion.

Due to this, all the bits in the key are rearranged again. We can observe that some of the bits get eliminated during the shifting process, producing a 48-bit key. This process is known as compression permutation.

Let's consider an RPT of the 32-bit size that is created in the IP stage. In this step, it is expanded from 32-bit to 48-bit. The RPT of 32-bit size is broken down into 8 chunks of 4 bits each and extra two bits are added to every chunk, later on, the bits are permutated among themselves leading to 48-bit data. An XOR function is applied in between the 48-bit key obtained from step 1 and the 48-bit expanded RPT.

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Triple DES is a symmetric key-block cipher which applies the DES cipher in triplicate. It encrypts with the first key (k1), decrypts using the second key (k2), then encrypts with the third key (k3). There is also a two-key variant, where k1 and k3 are the same keys.

Now in our understanding of what is DES, let us next look into the DES algorithm steps.

To put it in simple terms, DES takes 64-bit plain text and turns it into a 64-bit ciphertext. And since we’re talking about asymmetric algorithms, the same key is used when it’s time to decrypt the text.

The algorithm process breaks down into the following steps:

The encryption process step (step 4, above) is further broken down into five stages:

For decryption, we use the same algorithm, and we reverse the order of the 16 round keys.

Next, to better understand what is DES, let us learn the various modes of operation for DES.

Experts using DES have five different modes of operation to choose from.

We will next improve our understanding of what DES is, let us look into the DES implementation and testing.

DES implementation requires a security provider. However, there are many available providers to choose from, but selecting one is the essential initial step in implementation. Your selection may depend on the language you are using, such as Java, Python, C, or MATLAB.

Once you decide on a provider, you must choose whether to have a random secret key generated by the KeyGenerator or create a key yourself, using a plaintext or byte array.

It’s also essential to test the encryption to make sure it is properly implemented. You can find a testing procedure that will do the trick using the recurrence relation found on GitHub.     

Now that we have come so far in our understanding of what is DES, let us next look into the reasons to learn DES.

In this section, we are going to learn about some of the applications of the DES Algorithm.

Used to encrypt plain text of 64-bit

Used to encrypt plain text of 128-bit

The key is of 56-bit size.

The key is of different sizes such as 128-bits, 192-bits, and so on

It can be broken by brute force attacks

To date, AES has not been attacked

It is based on Feistel network

It is based on permutation and substitution network 

The advantages of the DES algorithm:

The disadvantages of the DES algorithm:

There are multiple steps involved in the steps for data encryption. They are:

The steps involved in the steps for data decryption are:

1. The order of the 16 48-bit keys is reversed such that key 16 becomes key 1, and so on. 

2. The steps for encryption are applied to the ciphertext.

Despite DES losing the lofty position of being the go-to data encryption standard algorithm, it’s still worth learning. There will always be room for the DES algorithm in cryptography because it was the foundation for subsequent encryption algorithms. If you understand the origins of data encryption, you will consequently have an easier time grasping the basics of current encryption methods.

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