DES Algorithm
By: Jash Patel
Tags: Algorithms, Security, Cryptography

In this article I discussed about the algorithm of Cryptography -DES (Data Encryption Algorithm).

First Of all What Is Cryptography and Why We Need It ? The prefix “Crypt” means “hidden” or “vault” and the suffix “graphy” stands for “writing.” It is Technique to Convert Plain Text into Cipher Text and vice versa. it refers to Secure information and communication techniques derived from mathematical concepts and a set of rule-based calculations called algorithms to transform messages in ways that are hard to decipher. These deterministic algorithms are used for cryptographic key generation and digital signing and verification to protect data privacy, web browsing on the internet and confidential communications such as credit card transactions and email.

It Works On Principle of ‘CIA’( Confidentiality,Integrity,Authentication).

DES(Data Encryption Standard) Algorithm :-

The DES algorithm is the most popular security algorithm. It’s a symmetric algorithm, which means that the same keys are used to encrypt/decrypt sensitive data. Key length is 8 byte (64 bit). So, to encrypt/decrypt data, the DES algorithm uses an 8-byte key, but 1 byte (8 bit) for parity checking. It’s a block cipher algorithm — that’s why the data block size of DES algorithm is 64 bit. To encrypt/decrypt data, the DES algorithm uses the Feistel structure. So, it uses some round to encrypt/decrypt data. Though data block size is 64 bit, the number of rounds will be 16 rounds. So, it will use different subkeys for each round. so the number of subkeys will be 16 subkeys.

Block cipher is a method of encrypting text (to produce ciphertext) in which a cryptographic key and algorithm are applied to a block of data (for example, 64 contiguous bits) at once as a group rather than to one bit at a time.

Block Cipher Algorithm

DES based on Feistel Cipher so it is uses

a) Round Function

b) Key Schedule

c) Initial and Final Permutation.

DES is based on the two fundamental attributes of cryptography: substitution (also called as confusion) and transposition (also called as diffusion). DES consists of 16 steps ,each of which is called as a round. Each round performs the steps of substitution and transposition. Let us now discuss the broad-level steps in DES.

In the first step, the 64 bit plain text block is handed over to an initial Permutation (IP) function. The initial permutation performed on plain text. Next the initial permutation (IP) produces two halves of the permuted block; says Left Plain Text (LPT) and Right Plain Text (RPT). Now each LPT and RPT to go through 16 rounds of encryption process. In the end, LPT and RPT are rejoined and a Final Permutation (FP) is performed on the combined block The result of this process produces 64 bit cipher text.

DES Algorithm

Advantages :-

DES does have the desirable properties of confusion and diffusion: each bit of ciphertext is based upon multiple bits of the key and changing a single bit of plaintext changes, on average, half of the bits of ciphertext.

Due to its Feistel structure and uncomplicated logic, DES is relatively easy to implement. However, it uses eight distinct S-Boxes, which increases its footprint (AES uses a single S-Box).

Disadvantages :-

The main disadvantage to DES is that it is broken using brute-force search.

DES is also vulnerable to attacks using linear cryptanalysis. However, it takes 247 known plaintexts to break DES in this manner.

In Des Key Size is Small (64 bit but it using 56 bit).

To Know More About Data Encryption Standard Algorithm. Hope This Is Helpful to You.

Thanks….

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