Rijndael algorithm (How to create our own Key )

Question

All the samples for Rijndael algorithm are defining the key from the Rijndael class itself, can\'t we provide the Key of our own. Any hint on this will help me a lot.

Th

Answer 1

The key property of the Rijndael instance takes a byte[] as the key. Make sure you set it to an array with a valid size for the algorithm.

Link to msdn: http://msdn.microsoft.com/en-us/library/system.security.cryptography.symmetricalgorithm.key.aspx

Answer 2

What do you mean by cannot provide the key of our own? Here's an example on how you do it.

public static string Encrypt(string Text, byte[] key, byte[] VectorBytes){
    try{
        byte[] TextBytes = Encoding.UTF8.GetBytes(Text);        
        RijndaelManaged rijKey = new RijndaelManaged();
        rijKey.Mode = CipherMode.CBC; 
        ICryptoTransform encryptor = rijKey.CreateEncryptor(key,VectorBytes); 
        MemoryStream memoryStream = new MemoryStream(); 
        cryptoStream.Write(TextBytes, 0, TextBytes.Length); 
        cryptoStream.FlushFinalBlock(); 
        byte[] cipherTextBytes = memoryStream.ToArray();
        memoryStream.Close();
        cryptoStream.Close(); 
        string cipherText = Convert.ToBase64String(cipherTextBytes); 
        return cipherText;
    } 
    catch (Exception e){
        MessageBox.Show("Falsches Passwort "+ e.Message.ToString());
        string t = "";
        return t;
    }
}

Answer 3

You can try something like this, based on the RijndaelManaged Class MSDN article that I also recommend you to read.

var plainText = "This will be encrypted.";
var aesAlg = new RijndaelManaged();
aesAlg.Key = new byte[32] { 118, 123, 23, 17, 161, 152, 35, 68, 126, 213, 16, 115, 68, 217, 58, 108, 56, 218, 5, 78, 28, 128, 113, 208, 61, 56, 10, 87, 187, 162, 233, 38 };
aesAlg.IV = new byte[16] { 33, 241, 14, 16, 103, 18, 14, 248, 4, 54, 18, 5, 60, 76, 16, 191};
ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

msEncrypt = new MemoryStream();
using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write)) {
    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt)) {
        swEncrypt.Write(plainText);
    }
}

return msEncrypt.ToArray();