Rijndael decryption in WinRT

Question

I'm trying to write a method that decrypts a byte array.

• the key is fixed and 24 bytes long

I get an exception The supplied user buffer is not valid for the requested operation when I do the actual decryption of the data, I hope someone can help me!

        // Get the key and put into IBuffers

        IBuffer keyBuffer = CryptographicBuffer.CreateFromByteArray(cKey);
        IBuffer plainText = CryptographicBuffer.CreateFromByteArray(cData);
        byte[] decryptedData;

        // Setup an AES key, using AES in CBC mode and applying PKCS#7 padding on the input
        SymmetricKeyAlgorithmProvider aesProvider = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.AesEcbPkcs7);
        CryptographicKey aesKeySymm = aesProvider.CreateSymmetricKey(keyBuffer);


        // Decrypt the data and convert it to byte array

        // EXCEPTION ON THIS LINE: "The supplied user buffer is not valid for the requested operation."
        IBuffer decrypted = CryptographicEngine.Decrypt(aesKeySymm, plainText, null);
        CryptographicBuffer.CopyToByteArray(decrypted, out decryptedData);
        return decryptedData;

Answer 1

CBC requires an IV (also a an IBuffer for CryptographicEngine.encrypt and CryptographicEngine.decrypt, so you cannot provide null. This is only written down for the encrypt function that the decrypt function references.