Datos incorrectos cuando cifrar y descifrar con TDES

Question

Estoy cifrar una gran cadena con TDES y tratando de descifrarlo. No se puede entender lo que es que está mal. Cuando lo hace la función READ en el desciframiento consigo "Bad datos" de la excepción de cifrado. (Me marcó la línea con los comentarios)

Para generar y cifrar la cadena:

public void MssGenerateKeyPair(string ssSymmetricKey, out string ssCipheredKeyPair, out string ssPublicKey) {
        ssCipheredKeyPair = string.Empty;
        ssPublicKey = string.Empty;

        //Symmetric key is the hash of user's signing password
        SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();
        byte[] tempKey = sha1.ComputeHash(Encoding.UTF8.GetBytes(ssSymmetricKey));
        byte[] key = new byte[24];
        tempKey.CopyTo(key, 0);
        //if symmetric keys is < 24
        for (int index = 0, i = tempKey.Length; i < key.Length; index++, i++)
        {
            key[i] = tempKey[index];
        }

        //define symmetric encryption data
        TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
        tdes.Key = key;
        tdes.IV = new byte[8];
        tdes.Mode = CipherMode.CBC;
        tdes.Padding = PaddingMode.PKCS7;

        //define assymetric stuff
        RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
        MemoryStream memoryStream = new MemoryStream();
        CryptoStream cryptoStream = new CryptoStream(memoryStream, tdes.CreateEncryptor(), CryptoStreamMode.Write);
        byte[] toChipher = Encoding.UTF8.GetBytes(rsa.ToXmlString(true));
        cryptoStream.Write(toChipher, 0, toChipher.Length);
        byte[] cipheredKeyPair = memoryStream.ToArray();
        ssCipheredKeyPair = Convert.ToBase64String(cipheredKeyPair);
        ssPublicKey = rsa.ToXmlString(false);
        cryptoStream.Close();
        memoryStream.Close();


    } // MssGenerateKeyPair

Para descifrar la cadena

public void MssSignData(string ssSymmetricKey, byte[] ssDataToSign, byte[] ssCipheredKeyPair, out byte[] ssSignature, out byte[] ssSignedData) {
        ssSignature = new byte[] {};
        ssSignedData = new byte[] {};

        //Symmetric key is the hash of user's signing password
        SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();
        byte[] tempKey = sha1.ComputeHash(Encoding.UTF8.GetBytes(ssSymmetricKey));
        byte[] key = new byte[24];
        tempKey.CopyTo(key, 0);
        //if symmetric keys is < 24
        for (int index = 0, i = tempKey.Length; i < key.Length; index++, i++)
        {
            key[i] = tempKey[index];
        }

        //define symmetric encryption data
        TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
        tdes.Key = key;
        tdes.IV = new byte[8];
        tdes.Mode = CipherMode.CBC;
        tdes.Padding = PaddingMode.PKCS7;

        MemoryStream memoryStream = new MemoryStream(ssCipheredKeyPair);
        CryptoStream cryptoStream = new CryptoStream(memoryStream, tdes.CreateDecryptor(), CryptoStreamMode.Read);
        MemoryStream plainMemoryStream = new MemoryStream();

        byte[] tempPlainBytes = new byte[1024];

        int read = 0;
        int totalRead = 0;
        do
        {
            //################################################################
            //ERROR IN THE FOLLOWING LINE
            //################################################################
            read = cryptoStream.Read(tempPlainBytes, 0, tempPlainBytes.Length);
            totalRead += read;
            plainMemoryStream.Write(tempPlainBytes, 0, read);
        } while (read > 0);

        RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
        rsa.FromXmlString(Encoding.UTF8.GetString(plainMemoryStream.ToArray()));

        ssSignature = rsa.SignData(ssDataToSign, new SHA1CryptoServiceProvider());
        ssSignedData = ssDataToSign;
        cryptoStream.Close();
        memoryStream.Close();
        plainMemoryStream.Close();

    } // MssSignData

Código de prueba

 private void button1_Click(object sender, EventArgs e)
    {
        string key;
        string pkey;
        byte[] sig;
        byte[] avs;

        OutSystems.NssPseudoCertificates.CssPseudoCertificates c = new OutSystems.NssPseudoCertificates.CssPseudoCertificates();

        c.MssGenerateKeyPair("xpto",out key, out pkey);
        c.MssSignString("xpto", "hello", key, out sig, out avs);


    }

Answer 1

Como dijo Marvin Smit en sus comentarios: añadir el color, lo hice y funcionó! Los créditos van a él!