Encrypt data in windows phone 8 using AES if I already have the key (as a string)

Question

I am working on a wp8 app that requires encryption and decryption. Actually I need a way to encrypt some data using AES. I already have the key(as a string). I need a c# equivalent for the below java code can somebody help?

public static String encryptWithAES(String payload, String aesKey) {

    byte[] raw = aesKey.getBytes();
    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES/ECB/PKCS5Padding");
    try {
        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);

        byte[] encrypted;
        encrypted = cipher.doFinal(payload.getBytes());
        cipher = null;
        return Base64.encodeToString(encrypted, Base64.DEFAULT);
    } catch (Exception e) {
        System.out.println("Error in encryptWithAES!!!");
        e.printStackTrace();
    }
    return null;
}

Here is what i did :

public static byte[] EncryptWithAES(string dataToEncrypt, String Key)
    {

        byte[] encryptedData;

        byte[] keyBytes = System.Text.Encoding.UTF8.GetBytes(Key);


        using (AesManaged aesEnc = new AesManaged())
        {
            aesEnc.Key = keyBytes;
            aesEnc.IV = new byte[16];

            //Create encryptor for converting
            ICryptoTransform encryptor = aesEnc.CreateEncryptor(aesEnc.Key, aesEnc.IV);


            using (MemoryStream memStream = new MemoryStream())
            {
                using (CryptoStream crypStream = new CryptoStream(memStream, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter srmWriter= new StreamWriter(crypStream))
                    {

                        srmWriter.Write(dataToEncrypt);
                    }
                    encryptedData = memStream.ToArray();
                }
            }
        }
        return encryptedData;
    }

The error I am getting is where i set the key: ie aesEnc.Key= keyBytes;

We are not a code translation service. Have you made an attempt at this yet? It is easier to help you when you have already started it. — gunr2171, Aug 18 '14 at 20:20
possible duplicate of [Using AES encryption in C#](http://stackoverflow.com/questions/273452/using-aes-encryption-in-c-sharp) — Elliott Frisch, Aug 18 '14 at 20:23
@gunr2171: I have already tried this. But sorry sir, with no fruit.I am new to this and am very sry if this kind of questions are not welcome here. @ Elliot: i referred that and tried. Idont know what is going wrong. Iam uploading my code here. Thanks for your replies — Akhil S A, Aug 18 '14 at 20:59

Jim Flood · Accepted Answer · 2014-08-19T16:37:28.427

1

Your C# code works fine. You write, "The error I am getting is where i set the key: ie aesEnc.Key= keyBytes;" but you don't mention what the error is. I would guess you are getting a Cryptographic Exception with message, "Specified key is not a valid size for this algorithm."

As an experiment, try this:

byte[] output = EncryptWithAES("Hello", Encoding.UTF8.GetString(new byte[16]));

or

byte[] output = EncryptWithAES("Hello", Encoding.UTF8.GetString(new byte[32]));

and see if you still get that error setting the key. That is, make sure your key string produces an array of either 16 or 32 bytes.

edited Aug 19 '14 at 16:37

answered Aug 18 '14 at 22:55

Jim Flood

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Thanks Jim. Was getting the error you mentioned.sorry for not mentioning it.Now I am able to execute the function without error(provided 16 byte key). But the return value is a string: "system.Byte[]". The passed key is:"1wted3e3l9c22sdvit5b14==". data is Hello world And I call the function in another page : byte[] ans = Encryption.EncryptWithAES("Hello world", key); – Akhil S A Aug 19 '14 at 00:21
Hi Jim, so silly of me.. This worked actually. I was trying to log the output using wrong method. I tried Convert.ToString() . It returned the string "system.byte[]". I used Convert.ToBase64String then ang got the answer. thanks a lot for the help – Akhil S A Aug 19 '14 at 00:43

Encrypt data in windows phone 8 using AES if I already have the key (as a string)

1 Answers1