c# implementations of AES encryption

Question

Hi,

I can't seem to find a nice clean example of using AES 128 bit encryption.

Does anyone have some sample code?

Answer 1

This article seems to discuss both the algorithm and a C# implementation that specifically includes 128 bit keysizes: http://msdn.microsoft.com/en-us/magazine/cc164055.aspx

There is a code sample available for download, attached to that article. The source code is available to browse online, here: http://msdn.microsoft.com/en-us/magazine/cc164846.aspx

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) http://msdn.microsoft.com/en-us/library/system.security.cryptography.rijndaelmanaged.aspx

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_Examples
{
    class RijndaelMemoryExample
    {
        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).
                RijndaelManaged myRijndael = new RijndaelManaged();

                // Encrypt the string to an array of bytes.
                byte[] encrypted = encryptStringToBytes_AES(original, myRijndael.Key, myRijndael.IV);  

                // Decrypt the bytes to a string.
                string roundtrip = decryptStringFromBytes_AES(encrypted, myRijndael.Key, myRijndael.IV);

                //Display the original data and the decrypted data.
                Console.WriteLine("Original:   {0}", original);
                Console.WriteLine("Round Trip: {0}", roundtrip);

            }
            catch (Exception e)
            {
                Console.WriteLine("Error: {0}", e.Message);
            }
        }

        static byte[] encryptStringToBytes_AES(string plainText, byte[] Key, byte[] IV)
        {
            // Check arguments.
            if (plainText == null || plainText.Length <= 0)
                throw new ArgumentNullException("plainText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("Key");

            // Declare the streams used
            // to encrypt to an in memory
            // array of bytes.
            MemoryStream    msEncrypt   = null;
            CryptoStream    csEncrypt   = null;
            StreamWriter    swEncrypt   = null;

            // Declare the RijndaelManaged object
            // used to encrypt the data.
            RijndaelManaged aesAlg      = null;

            try
            {
                // Create a RijndaelManaged object
                // with the specified key and IV.
                aesAlg = new RijndaelManaged();
                aesAlg.Key = Key;
                aesAlg.IV = IV;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for encryption.
                msEncrypt = new MemoryStream();
                csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write);
                swEncrypt = new StreamWriter(csEncrypt);

                //Write all data to the stream.
                swEncrypt.Write(plainText);

            }
            finally
            {
                // Clean things up.

                // Close the streams.
                if(swEncrypt != null)
                    swEncrypt.Close();
                if (csEncrypt != null)
                    csEncrypt.Close();
                if (msEncrypt != null)
                    msEncrypt.Close();

                // Clear the RijndaelManaged object.
                if (aesAlg != null)
                    aesAlg.Clear();
            }

            // Return the encrypted bytes from the memory stream.
            return msEncrypt.ToArray();

        }

        static string decryptStringFromBytes_AES(byte[] cipherText, byte[] Key, byte[] IV)
        {
            // Check arguments.
            if (cipherText == null || cipherText.Length <= 0)
                throw new ArgumentNullException("cipherText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("Key");

            // TDeclare the streams used
            // to decrypt to an in memory
            // array of bytes.
            MemoryStream    msDecrypt   = null;
            CryptoStream    csDecrypt   = null;
            StreamReader    srDecrypt   = null;

            // Declare the RijndaelManaged object
            // used to decrypt the data.
            RijndaelManaged aesAlg      = null;

            // Declare the string used to hold
            // the decrypted text.
            string plaintext = null;

            try
            {
                // Create a RijndaelManaged object
                // with the specified key and IV.
                aesAlg = new RijndaelManaged();
                aesAlg.Key = Key;
                aesAlg.IV = IV;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for decryption.
                msDecrypt = new MemoryStream(cipherText);
                csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read);
                srDecrypt = new StreamReader(csDecrypt);

                // Read the decrypted bytes from the decrypting stream
                // and place them in a string.
                plaintext = srDecrypt.ReadToEnd();
            }
            finally
            {
                // Clean things up.

                // Close the streams.
                if (srDecrypt != null)
                    srDecrypt.Close();
                if (csDecrypt != null)
                    csDecrypt.Close();
                if (msDecrypt != null)
                    msDecrypt.Close();

                // Clear the RijndaelManaged object.
                if (aesAlg != null)
                    aesAlg.Clear();
            }

            return plaintext;

        }
    }
}

Answer 2

Using AES or implementing AES? To use AES, there is the System.Security.Cryptography.RijndaelManaged class.

Answer 3

For a more complete example that performs key derivation in addition to the AES encryption, see the answer and links posted in Getting AES encryption to work across Javascript and C#.