A simple guide to get you started with AES encryption in C#

Using AES (Advanced Encryption Standard) encryption in C# involves several steps, including selecting the appropriate AES variant, handling keys, and implementing encryption and decryption routines. Below is a simple guide to get you started with AES encryption in C#.

1. Choose AES Variant:

   Decide on the AES variant to use (AES-128, AES-192, or AES-256). This choice will determine the key size and the level of security.

2. Create a Key:

   Generate a secure random key of the appropriate size using a cryptographic library. In C#, you can use RNGCryptoServiceProvider for this purpose.

   csharp

   using System.Security.Cryptography;

   byte[] key = new byte[16]; // for AES-128

   using (var rng = new RNGCryptoServiceProvider())

   {

       rng.GetBytes(key);

   }

   

3. Choose a Mode and Padding:

   Decide on the mode of operation (e.g., CBC, GCM) and the padding scheme (e.g., PKCS7). These choices affect how the data is processed during encryption and decryption.

4. Implement Encryption:

   Use the AesManaged class from the System.Security.Cryptography namespace for encryption. Heres a simple example:

   csharp

   using System;

   using System.IO;

   using System.Security.Cryptography;

   using System.Text;

   public class AesEncryption

   {

       public static byte[] Encrypt(string plainText, byte[] key, byte[] iv)

       {

           using (AesManaged aesAlg = new AesManaged())

           {

               aesAlg.Key = key;

               aesAlg.IV = iv;

               ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

               using (MemoryStream msEncrypt = new MemoryStream())

               {

                   using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))

                   {

                       using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))

                       {

                           swEncrypt.Write(plainText);

                       }

                   }

                   return msEncrypt.ToArray();

               }

           }

       }

   }

   

5. Implement Decryption:

   Implement a similar decryption method using the AesManaged class.

   csharp

   public class AesEncryption

   {

       // ... (previous code)

       public static string Decrypt(byte[] cipherText, byte[] key, byte[] iv)

       {

           using (AesManaged aesAlg = new AesManaged())

           {

               aesAlg.Key = key;

               aesAlg.IV = iv;

               ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

               using (MemoryStream msDecrypt = new MemoryStream(cipherText))

               {

                   using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))

                   {

                       using (StreamReader srDecrypt = new StreamReader(csDecrypt))

                       {

                           return srDecrypt.ReadToEnd();

                       }

                   }

               }

           }

       }

   }

   

6. Usage Example:

   Now, you can use the Encrypt and Decrypt methods in your application.

   csharp

   byte[] iv = new byte[16]; // Initialization Vector, should be unique for each encryption

   string plaintext = "Hello, AES!";

   byte[] encrypted = AesEncryption.Encrypt(plaintext, key, iv);

   string decrypted = AesEncryption.Decrypt(encrypted, key, iv);

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

   Console.WriteLine($"Encrypted: {Convert.ToBase64String(encrypted)}");

   Console.WriteLine($"Decrypted: {decrypted}");

   

This is a basic guide, and real-world implementations should consider additional security aspects, such as key management and secure random number generation. Always handle encryption keys securely and follow best practices for cryptographic operations.