How to Encrypt/Decrypt using AES in WinRT?

Question

I am newbie in Cryptography.

Edited: It seems that I was wrong with using the right Encrypt/Decrypt algorithm so I change my question to:

How to convert these lines of codes to WinRT ?

The code is based on the code at http://msdn.microsoft.com/en-us/library/system.security.cryptography.aesmanaged.aspx

I need to do the same in WinRT:

Update:

There is a Cryptography and Certificate sample for WinRT (Windows 8.1) that solved my problem.

Please check: http://code.msdn.microsoft.com/windowsapps/Cryptography-and-3305467b

public static byte[] Encrypt(string plainText)
    {
        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");
        byte[] encrypted;
        using (AesManaged aesAlg = new AesManaged())
        {
            aesAlg.Key = Key;
            aesAlg.IV = IV;

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

            using (MemoryStream msEncrypt = new MemoryStream())
            {
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                    {
                        //Write all data to the stream.
                        swEncrypt.Write(plainText);
                    }
                    encrypted = msEncrypt.ToArray();
                }
            }
        }
        return encrypted;
    }

And

public static string Decrypt(byte[] cipherText)
    {
        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");

        string plaintext = null;

        using (AesManaged aesAlg = new AesManaged())
        {
            aesAlg.Key = Key;
            aesAlg.IV = IV;

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

            using (MemoryStream msDecrypt = new MemoryStream(cipherText))
            {
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                {
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                    {

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

        }

        return plaintext;

    }

Answer 1

Yes it is possible, but you should use the same:

• character encoding of the plaintext, such as UTF-8
• mode of operation
• padding algorithm
• (optional) string encoding of the ciphertext, such as base64 encoding or the easier to debug hexadecimal encoding

And of course the correct cipher (AES instead of Rijndael),symmetric key size and value and IV . Make sure you check each of the IO to these functions separately . Do not rely on defaults, set each value explicitly.

Note that using ECB mode is insecure. Currently you are probably mixing CBC and ECB mode, which won't work. For secure communications you should use authenticated encryption or a MAC (using a second key).