Introduction

Hello everyone!

If you are interested in encryption algorithms, then the DES algorithm is certainly a topic you cannot avoid.

DES is like the classic sports car of the encryption world—debuting in 1977, it once enjoyed great popularity. Although it is no longer the safest choice today, DES remains a very interesting and useful tool for learning the fundamentals of cryptography and in certain specific application scenarios.

Today, we will discuss the DES algorithm for encryption and decryption. Are you ready? Let’s embark on this interesting journey of exploration together!

Principle

The DES algorithm is a type of symmetric encryption algorithm (the same key is used for both encryption and decryption), utilizing 64-bit blocks and a 56-bit key (actually 64 bits, but 8 bits are used for parity).

Its core is the Feistel network structure, which disrupts data through 16 rounds of confusion and diffusion operations.

Advantages

• The DES algorithm is public, simple in structure, and easy to implement.

• The DES algorithm executes quickly, making it suitable for low-security scenarios such as internal systems and temporary encryption.

Disadvantages

• The key length of the DES algorithm is too short, at only 56 bits, making it vulnerable to brute-force attacks, which can be cracked in just a few hours.

Implementation Code

The implementation of the DES algorithm for encryption and decryption is very straightforward:

using System;
using System.Security.Cryptography;
using System.Text;

public class DESExample
{
    public static void Main()
    {
        // Original data
        string originalText = "Hello, DES!";

        Console.WriteLine($"Original: {originalText}");

        // Define key and initialization vector, note they must be 8 bytes long
        string key = "abcdefgh"; // Must be 8 characters
        string iv = "ijklmnop";  // Must be 8 characters  

        // Initialize key and vector
        byte[] byKey = Encoding.UTF8.GetBytes(key);
        byte[] byIV = Encoding.UTF8.GetBytes(iv);

        // Encrypt
        string encryptedText = EncryptDES(originalText, byKey, byIV);
        Console.WriteLine($"Encrypted: {encryptedText}");

        // Decrypt
        string decryptedText = DecryptDES(encryptedText, byKey, byIV);
        Console.WriteLine($"Decrypted: {decryptedText}");
    }

    // DES encryption
    private static string EncryptDES(string plainText, byte[] byKey, byte[] byIV)
    {
        using (DESCryptoServiceProvider des = new DESCryptoServiceProvider())
        {
            ICryptoTransform encryptor = des.CreateEncryptor(byKey, byIV);
            using (MemoryStream ms = new MemoryStream())
            {
                // Use CryptoStream for streaming decryption to avoid memory issues with large files
                using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter sw = new StreamWriter(cs))
                    {
                        sw.Write(plainText);
                    }
                }
                return Convert.ToBase64String(ms.ToArray());
            }
        }
    }

    // DES decryption
    private static string DecryptDES(string cipherText, byte[] byKey, byte[] byIV)
    {
        using (DESCryptoServiceProvider des = new DESCryptoServiceProvider())
        {
            ICryptoTransform decryptor = des.CreateDecryptor(byKey, byIV);
            using (MemoryStream ms = new MemoryStream(Convert.FromBase64String(cipherText)))
            {
                // Use CryptoStream for streaming decryption to avoid memory issues with large files
                using (CryptoStream cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
                {
                    using (StreamReader sr = new StreamReader(cs))
                    {
                        return sr.ReadToEnd();
                    }
                }
            }
        }
    }
}

Conclusion

In today’s world, where information security is increasingly emphasized, the importance of encryption technology is undeniable.

Although modern encryption algorithms like AES are more commonly seen today, DES, as a “senior” symmetric encryption algorithm, holds an important place in history.

Understanding DES not only helps us grasp the evolution of encryption algorithms but also provides insights for addressing complex encryption needs.

Well, that’s all for today’s sharing! If you found it useful, don’t forget to give it a thumbs up and let me know you’re watching! Your support is my greatest motivation!

Finally, if you have better ideas or suggestions, feel free to leave a comment for discussion!

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I am Lao Yang, a passionate programmer with over 10 years of experience, currently working on the front lines. I am a software project manager and a happy coder, continuously sharing practical programming skills, project management experiences, and career growth insights for free. Join me every Monday, Wednesday, and Friday at 7:20 AM for our rendezvous! Welcome to follow along as we explore the mysteries of the coding world together!

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