INTRODUCTION
Cryptography is used everywhere today — from passwords to secure messages.
One of the earliest and most popular encryption algorithms is DES
(Data Encryption Standard).
In this blog, I will explain DES in a very simple way,
using easy language, screenshots from code, and clear diagrams.
Even beginners can understand how DES works.
WHAT IS DES?
DES (Data Encryption Standard) is a symmetric key encryption algorithm.
This means the same secret key is used for both encryption and decryption.
DES was developed in the 1970s and works on fixed-size data blocks.
Even though DES is no longer considered secure today,
it is very important to understand it for learning cryptography basics.
BASIC DETAILS OF DES
• Type: Symmetric key encryption
• Block size: 64 bits
• Key size: 56 bits
• Number of rounds: 16
HOW DES WORKS
DES works by repeatedly mixing the data using a secret key.
The input text is split into two halves and processed for 16 rounds.
Each round increases confusion and diffusion,
making the encrypted data difficult to understand without the key.
STEP-BY-STEP WORKING OF DES
Plain Text Input
DES takes 64 bits of plain text as input.
This text is divided into two equal halves:
Left (32 bits) and Right (32 bits).
One DES Round
Each DES round follows the same pattern:
1. The Right part is processed using a function called f().
2. The output of f() is XORed with the Left part.
3. The Left and Right parts are swapped.
Formula
New Left = Old Right
New Right = Old Left XOR f(Old Right, Key)
Why 16 Rounds
DES repeats the same process 16 times.
Each round increases security by mixing the data further.
After 16 rounds, the final output becomes the cipher text.
ENCRYPTION PROCESS
Below is a simple demonstration of DES encryption.
The same plain text and key always produce the same cipher text.
DECRYPTION PROCESS
DES decryption uses the same algorithm in reverse order.
The same secret key is required to recover the original plain text.
ENCRYPTION vs DECRYPTION
| Feature | Encryption | Decryption |
| | | |
| Input | Plain Text | Cipher Text |
| Key | Same Secret Key | Same Secret Key |
| Output | Cipher Text | Plain Text |
LIMITATIONS OF DES
• Small key size (56 bits)
• Vulnerable to brute-force attacks
• No longer secure for modern applications
DES vs MODERN ALGORITHMS
Due to its weaknesses, DES has been replaced by stronger algorithms like AES.
However, DES is still widely taught for understanding
the foundations of encryption systems.
CONCLUSION
DES is a classic encryption algorithm that helps beginners
understand how block ciphers work.
While it should not be used in real-world security today,
learning DES provides a strong base for understanding modern cryptography.
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