Convert RijndaelManaged code to AesManaged code

Question

I got this block of code:

    public static string DoPrefixCipherEncrypt(string strIn, byte[] btKey)
    {
        if (strIn.Length < 1)
            return strIn;

        // Convert the input string to a byte array 
        byte[] btToEncrypt = System.Text.Encoding.Unicode.GetBytes(strIn);
        RijndaelManaged cryptoRijndael = new RijndaelManaged();
        cryptoRijndael.Mode =
        CipherMode.ECB;//Doesn't require Initialization Vector 
        cryptoRijndael.Padding =
        PaddingMode.PKCS7;


        // Create a key (No IV needed because we are using ECB mode) 
        ASCIIEncoding textConverter = new ASCIIEncoding();

        // Get an encryptor 
        ICryptoTransform ictEncryptor = cryptoRijndael.CreateEncryptor(btKey, null);


        // Encrypt the data... 
        MemoryStream msEncrypt = new MemoryStream();
        CryptoStream csEncrypt = new CryptoStream(msEncrypt, ictEncryptor, CryptoStreamMode.Write);


        // Write all data to the crypto stream to encrypt it 
        csEncrypt.Write(btToEncrypt, 0, btToEncrypt.Length);
        csEncrypt.Close();


        //flush, close, dispose 
        // Get the encrypted array of bytes 
        byte[] btEncrypted = msEncrypt.ToArray();


        // Convert the resulting encrypted byte array to string for return 
        return (Convert.ToBase64String(btEncrypted));
    }

    private static List<int> GetRandomSubstitutionArray(string number)
    {
        // Pad number as needed to achieve longer key length and seed more randomly.
        // NOTE I didn't want to make the code here available and it would take too longer to clean, so I'll tell you what I did. I basically took every number seed that was passed in and prefixed it and  postfixed it with some values to make it 16 characters long and to get a more unique result. For example:
        // if (number.Length = 15)
        //    number = "Y" + number;
        // if (number.Length = 14)
        //    number = "7" + number + "z";
        // etc - hey I already said this is a hack ;)

        // We pass in the current number as the password to an AES encryption of each of the
        // digits 0 - 9. This returns us a set of values that we can then sort and get a 
        // random order for the digits based on the current state of the number.
        Dictionary<string, int> prefixCipherResults = new Dictionary<string, int>();
        for (int ndx = 0; ndx < 10; ndx++)
            prefixCipherResults.Add(DoPrefixCipherEncrypt(ndx.ToString(), Encoding.UTF8.GetBytes(number)), ndx);

        // Order the results and loop through to build your int array.
        List<int> group = new List<int>();
        foreach (string key in prefixCipherResults.Keys.OrderBy(k => k))
            group.Add(prefixCipherResults[key]);

        return group;
    }

from this link Encrypt a number to another number of the same length

I need the "DoPrefixCypherEncrypt" converted/adjusted to AesManaged instead of RijdaelManaged.

Thanks guys

UPDATE: Thanks for all your answers:

I eventually found another way to do it using the available classes in WP 8.1.

Instead of:

        public static string DoPrefixCipherEncrypt(string strIn, byte[] btKey)
    {
        if (strIn.Length < 1)
            return strIn;

        // Convert the input string to a byte array 
        byte[] btToEncrypt = System.Text.Encoding.Unicode.GetBytes(strIn);

        AesManaged cryptoRijndael = new AesManaged();
        cryptoRijndael.Mode = CipherMode.ECB; cryptoRijndael.Padding = PaddingMode.PKCS7; //Mode Doesn't require Initialization Vector 

        // Create a key (No IV needed because we are using ECB mode) 
        ASCIIEncoding textConverter = new ASCIIEncoding();
        // Get an encryptor 
        ICryptoTransform ictEncryptor = cryptoRijndael.CreateEncryptor(btKey, null);
        // Encrypt the data... 
        MemoryStream msEncrypt = new MemoryStream();
        CryptoStream csEncrypt = new CryptoStream(msEncrypt, ictEncryptor, CryptoStreamMode.Write);

        // Write all data to the crypto stream to encrypt it 
        csEncrypt.Write(btToEncrypt, 0, btToEncrypt.Length); csEncrypt.Close(); //flush, close, dispose 
        // Get the encrypted array of bytes 
        byte[] btEncrypted = msEncrypt.ToArray();

        // Convert the resulting encrypted byte array to string for return 
        return (Convert.ToBase64String(btEncrypted));
    }

which is compatible with non WinRT .NET.

I was able to use:

    public static string DoPrefixCipherEncrypt(string strIn, byte[] btKey)
    {
        if (strIn.Length < 1)
            return strIn;

        IBuffer plainBuffer = CryptographicBuffer.ConvertStringToBinary(strIn, BinaryStringEncoding.Utf16LE);
        IBuffer keyMaterial = CryptographicBuffer.CreateFromByteArray(btKey);

        SymmetricKeyAlgorithmProvider symProvider = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.AesEcbPkcs7);
        // create symmetric key from derived password key
        CryptographicKey symmKey = symProvider.CreateSymmetricKey(keyMaterial);

        var buffEncrypted = CryptographicEngine.Encrypt(symmKey, plainBuffer, null);
        var strEncrypted = CryptographicBuffer.EncodeToBase64String(buffEncrypted);

        return strEncrypted;
    }

I don't understand the question - Are you aware that Rijndael algorithm and AES is actually the same thing? — Marwie, Aug 29 '14 at 08:56
I want to use this encryption in Windows/Phone 8.1 does not use the System.Security.Cryptography so my question is I need a code I can use with Windows.Security.Cryptography classes or any other applicable one. Thanks — bolaji, Aug 29 '14 at 09:01

score 1 · Answer 1 · edited May 23 '17 at 10:28

Just replace the instantiation and declaration of RijndaelManaged with AesManaged:

AesManaged cryptoRijndael = new AesManaged();

I tried it and it works just fine. I'd recommend to do a rename of the cryptoRijndael variable name as well - but that won't change anything on the functioning of the code.

There is an example on MSDN how to use AesManaged with the following statement:

The AES algorithm is essentially the Rijndael symmetric algorithm with a fixed block size and iteration count. This class functions the same way as the RijndaelManaged class but limits blocks to 128 bits and does not allow feedback modes.

So just replace the references of RijndaelManaged with AesManaged. As long as your not using it outside the described limitations you should be fine.

Strictly speaking, AES is a subset of Rijndael so the Rijndael Managed should already cover anything you need.

From Wikipedia:

AES is based on the Rijndael cipher[5] developed by two Belgian cryptographers, Joan Daemen and Vincent Rijmen, who submitted a proposal to NIST during the AES selection process.

Thanks. Windows/Phone 8.1 doesn't have Rijndael , but I learnt it has AesManaged — bolaji, Aug 29 '14 at 09:04
Sorry, there is no class AesManaged in WinRT. I eventually found another way to do it — bolaji, Sep 01 '14 at 21:45
NOTE: This answer also applies to Windows' .NET Framework, not just to Windows Mobile 8.x — Matt, Jun 22 '17 at 13:42

Convert RijndaelManaged code to AesManaged code

1 Answers1