CODEWITHSUNDEEP
c#xmlencryption
Tomtom
Tomtom

Reputation: 9384

Write encrypted data to xml

In my application I have the following code for the encryption of some data as string:

private string EncryptPermission(User user)
{
    Encoding encoding = Encoding.ASCII;
    Cryptography cryptography = CreateCryptography(user);
    byte[] val = encoding.GetBytes(user.Permission.ToString());
    byte[] encrypted = cryptography.Encrypt(val);
    string result = encoding.GetString(encrypted);
    return result;
}

That works like I want. Now I want to write that data to an xml-file like:

internal void WriteUser(User user)
{
    XElement userElement = new XElement("user",
        new XAttribute("id", user.UserId.ToString("N")),
        new XElement("name", user.Username),
        new XElement("password", user.Password),
        new XElement("permission", EncryptPermission(user)));

    XDocument document = GetDocument();
    if (document.Root != null)
    {
        document.Root.Add(userElement);
        SaveDocument(document);
    }
}

At the moment I call SaveDocument I get an Exception like:

A first chance exception of type 'System.ArgumentException' occurred in System.Xml.dll

Additional information: ' ', hexadecimal value 0x06, is a invalid char.

(Translated from german)

How can I solve this? I've already tried to use Converter.ToBase64String(..) and Converter.FromBase64String(..) but there I get an exception that the data is too long.

Upvotes: 0

Views: 315

Answers (2)

rossum
rossum

Reputation: 15685

Encryption produces bytes, and not all bytes are valid characters, as expected by XML. Your 0x06 is just one such. One possible solution is to convert the bytes into Base64 before writing to XML. Base64 uses only valid characters, at the cost of some increase in size: it uses four characters to write three bytes.

Have a look at the Convert class for the C# Base64 conversion methods.

Upvotes: 1

Chris Cooper
Chris Cooper

Reputation: 389

It mostly likely down to a character within the string, has broken the xml.

Add the encrypted string in a CDATA[] tags, within the nodes and you should be fine

What does <![CDATA[]]> in XML mean?

Upvotes: 0

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