Using AES encryption in C#

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I can't seem to find a nice clean example of using AES 128 bit encryption. Does anyone have some sample code?

10 Answers 10

If you just want to use the built-in crypto provider RijndaelManaged, check out the following help article (it also has a simple code sample):

And just in case you need the sample in a hurry, here it is in all its plagiarized glory:

using System; using System.IO; using System.Security.Cryptography; namespace RijndaelManaged_Example < class RijndaelExample < public static void Main() < try < string original = "Here is some data to encrypt!"; // Create a new instance of the RijndaelManaged // class. This generates a new key and initialization // vector (IV). using (RijndaelManaged myRijndael = new RijndaelManaged()) < myRijndael.GenerateKey(); myRijndael.GenerateIV(); // Encrypt the string to an array of bytes. byte[] encrypted = EncryptStringToBytes(original, myRijndael.Key, myRijndael.IV); // Decrypt the bytes to a string. string roundtrip = DecryptStringFromBytes(encrypted, myRijndael.Key, myRijndael.IV); //Display the original data and the decrypted data. Console.WriteLine("Original: ", original); Console.WriteLine("Round Trip: ", roundtrip); > > catch (Exception e) < Console.WriteLine("Error: ", e.Message); > > static byte[] EncryptStringToBytes(string plainText, byte[] Key, byte[] IV) < // Check arguments. if (plainText == null || plainText.Length encrypted = msEncrypt.ToArray(); > > > // Return the encrypted bytes from the memory stream. return encrypted; > static string DecryptStringFromBytes(byte[] cipherText, byte[] Key, byte[] IV) < // Check arguments. if (cipherText == null || cipherText.Length > > > return plaintext; > > > 

Your code doesn't store the IV along with the ciphertext, making it hard to use correctly, and easy to abuse. An IV isn't a secondary key, it should be randomly generated for each encryption, and stored alongside the ciphertext.

Sure, there you go. msdn.microsoft.com/de-de/library/… Take a look at remarks. You can use rijndael but it could lead to compatibility issues, when you channge settings. Therefor I would use Aes-Class if you want to encrypt with AES(FIPS-197)

@EricJ. The using () block automatically disposes the myRijndael object (and every other RijndaelManaged object in this example). Perhaps your comment was for an earlier version of the answer, or the link were showing bad examples, but that's not the case today.

I've recently had to bump up against this again in my own project - and wanted to share the somewhat simpler code that I've been using, as this question and series of answers kept coming up in my searches.

I'm not going to get into the security concerns around how often to update things like your Salt and Initialization Vector - that's a topic for a security forum, and there are some great resources out there to look at. This is simply a block of code to implement AesManaged in C#.

using System; using System.IO; using System.Security.Cryptography; using System.Text; namespace Your.Namespace.Security < public static class Cryptography < #region Settings private static int _iterations = 2; private static int _keySize = 256; private static string _hash = "SHA1"; private static string _salt = "aselrias38490a32"; // Random private static string _vector = "8947az34awl34kjq"; // Random #endregion public static string Encrypt(string value, string password) < return Encrypt(value, password); > public static string Encrypt(string value, string password) where T : SymmetricAlgorithm, new() < byte[] vectorBytes = GetBytes(_vector); byte[] saltBytes = GetBytes(_salt); byte[] valueBytes = GetBytes(value); byte[] encrypted; using (T cipher = new T()) < PasswordDeriveBytes _passwordBytes = new PasswordDeriveBytes(password, saltBytes, _hash, _iterations); byte[] keyBytes = _passwordBytes.GetBytes(_keySize / 8); cipher.Mode = CipherMode.CBC; using (ICryptoTransform encryptor = cipher.CreateEncryptor(keyBytes, vectorBytes)) < using (MemoryStream to = new MemoryStream()) < using (CryptoStream writer = new CryptoStream(to, encryptor, CryptoStreamMode.Write)) < writer.Write(valueBytes, 0, valueBytes.Length); writer.FlushFinalBlock(); encrypted = to.ToArray(); >> > cipher.Clear(); > return Convert.ToBase64String(encrypted); > public static string Decrypt(string value, string password) < return Decrypt(value, password); > public static string Decrypt(string value, string password) where T : SymmetricAlgorithm, new() < byte[] vectorBytes = GetBytes(_vector); byte[] saltBytes = GetBytes(_salt); byte[] valueBytes = Convert.FromBase64String(value); byte[] decrypted; int decryptedByteCount = 0; using (T cipher = new T()) < PasswordDeriveBytes _passwordBytes = new PasswordDeriveBytes(password, saltBytes, _hash, _iterations); byte[] keyBytes = _passwordBytes.GetBytes(_keySize / 8); cipher.Mode = CipherMode.CBC; try < using (ICryptoTransform decryptor = cipher.CreateDecryptor(keyBytes, vectorBytes)) < using (MemoryStream from = new MemoryStream(valueBytes)) < using (CryptoStream reader = new CryptoStream(from, decryptor, CryptoStreamMode.Read)) < decrypted = new byte[valueBytes.Length]; decryptedByteCount = reader.Read(decrypted, 0, decrypted.Length); >> > > catch (Exception ex) < return String.Empty; >cipher.Clear(); > return Encoding.UTF8.GetString(decrypted, 0, decryptedByteCount); > > > 

The code is very simple to use. It literally just requires the following:

string encrypted = Cryptography.Encrypt(data, "testpass"); string decrypted = Cryptography.Decrypt(encrypted, "testpass"); 

By default, the implementation uses AesManaged - but you could actually also insert any other SymmetricAlgorithm . A list of the available SymmetricAlgorithm inheritors for .NET 4.5 can be found at:

As of the time of this post, the current list includes:

• AesManaged
• RijndaelManaged
• DESCryptoServiceProvider
• RC2CryptoServiceProvider
• TripleDESCryptoServiceProvider

To use RijndaelManaged with the code above, as an example, you would use:

string encrypted = Cryptography.Encrypt(dataToEncrypt, password); string decrypted = Cryptography.Decrypt(encrypted, password); 

I hope this is helpful to someone out there.