CODEWITHSUNDEEP
c#aes
MikeS159
MikeS159

Reputation: 1974

Using SharpAESCrypt to encrypt strings

I decided to use the SharpAESCrypt implementation of AES encryption in C#. According to their documentation (https://www.aescrypt.com/sharp_aes_crypt.html) you should be able to use a static method, providing a password string, plain-text input stream and a output stream. The data I get out of my output stream appears to be all zero's.

I suspect I am doing something wrong converting strings to a stream and back. Can anyone see anything that is obviously wrong with the code below? (It compiles and runs, but the newByteArray is filled with 0's at the end)

    private void encryptMemStream()
    {
        byte[] byteArray = Encoding.UTF8.GetBytes(DecryptedTB.Text);
        using (MemoryStream plainText = new MemoryStream(byteArray))
        {
            using (MemoryStream encryptedData = new MemoryStream())
            {
                //plainText.Write(byteArray, 0, byteArray.Length);
                SharpAESCrypt.Encrypt(PasswordTB.Text, plainText, encryptedData);
                encryptedData.Position = 0;
                byte[] newByteArray = new byte[encryptedData.Length];
                newByteArray = encryptedData.ToArray();
                EncryptedTB.Text = Encoding.UTF8.GetString(newByteArray);
            }
        }
    }

Edit: The native implementation of this code uses fileStreams, but it should work with MemoryStreams too. I will test filestreams and add my results here.

More Edits:

So when you use a file stream you call this code

    //Code from the AES Crypt Library
    public static void Encrypt(string password, string inputfile, string outputfile)
    {
        using (FileStream infs = File.OpenRead(inputfile))
        using (FileStream outfs = File.Create(outputfile))
            Encrypt(password, infs, outfs);
    }

Which calls a function which I have been calling directly

    //Code from the AES Crypt Library
    public static void Encrypt(string password, Stream input, Stream output)
    {
        int a;
        byte[] buffer = new byte[1024 * 4];
        SharpAESCrypt c = new SharpAESCrypt(password, output, OperationMode.Encrypt);
        while ((a = input.Read(buffer, 0, buffer.Length)) != 0)
            c.Write(buffer, 0, a);
        c.FlushFinalBlock();
    }

There is obviously some subtle difference in using a MemoryStream and a FileStream which I don't understand. FileStream works fine, where as MemoryStream returns a blank array...

Upvotes: 3

Views: 1031

Answers (1)

Chris
Chris

Reputation: 27627

A quick code review reveals a few things including what, from discussion, seems to be the main problem you are facing. The problematic line is 

EncryptedTB.Text = Encoding.UTF8.GetString(newByteArray);

This line is taking the binary data in newByteArray and telling your code that it is a valid UTF8 byte array. Chances are that it is almost certainly not actually going to be valid UTF8. Parts of it may be (such as the header) but the actually encrypted data is not going to be and so you shouldn't use this method to get a string.

If you need a printable string to put in a textbox of some sort then the correct way to do this for binary data is through base64 encoding.

EncryptedTB.Text = Convert.ToBase64String(newByteArray);

Base64 encoding effectively takes groups of three bytes (24 bits) and converts them to groups of four characters.

A further note while I'm here is that in these two lines:

byte[] newByteArray = new byte[encryptedData.Length];
newByteArray = encryptedData.ToArray();

You declare a byte array and allocate a new array to it. You then immediately discard this in favour of the array from encryptedData.ToArray(). This does not put data into the array allocated by new byte[encryptedData.Length] but creates a new array and puts it into the newByteArray variable. Better would be to just do:

byte[] newByteArray = encryptedData.ToArray();

Full working code below:

byte[] byteArray = Encoding.UTF8.GetBytes(sourceText);
Byte[] newByteArray;
using (MemoryStream plainText = new MemoryStream(byteArray))
{
    using (MemoryStream encryptedData = new MemoryStream())
    {
        SharpAESCrypt.Encrypt(password, plainText, encryptedData);
        newByteArray = encryptedData.ToArray();
    }
}
EncryptedTB.Text = Convert.ToBase64String(newByteArray);

Upvotes: 2

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