MD5 Hash in C# doesn't match MD5 Hash in Action Script

Question

Hi,

I'm hashing some data in Action Script then comparing the hash to one computed in C#, but they don't match.

Anyone know why?

Here's what I do in Action script:

    var hash : String = MD5.hash(theString);

And here's what I do in C#:

    var md5Hasher = MD5.Create();
    byte[] data = md5Hasher.ComputeHash(Encoding.UTF8.GetBytes(theSameString));
    var sBuilder = new StringBuilder();

    for (int i = 0; i < data.Length; i++)
    {
        sBuilder.Append(data[i].ToString("x2"));
    }
    var hash = sBuidler.ToString();

I'm thinking it's an encoding thing, but can't put my finger on it... let me know!

-Ev

Answer 1

Strings in ActionScript are in UTF-16 encoding.

Answer 2

ActionScript must be using a different string encoding, but it is unclear to me which (I tried to google but it’s very hard to find).

Therefore, I recommend you try the following:

Console.WriteLine(ToHex(MD5.Create().ComputeHash(Encoding.UTF8.GetBytes("ä"))));
Console.WriteLine(ToHex(MD5.Create().ComputeHash(Encoding.Unicode.GetBytes("ä"))));
Console.WriteLine(ToHex(MD5.Create().ComputeHash(Encoding.GetEncoding("ISO-8859-1").GetBytes("ä"))));

(Of course, ToHex is the function that you already wrote to turn things into into hexadecimal:)

static string ToHex(byte[] data)
{
    var sBuilder = new StringBuilder();
    for (int i = 0; i < data.Length; i++)
        sBuilder.Append(data[i].ToString("x2"));
    return sBuilder.ToString();
}

And then check to see which of the three hashes you get is the same as the one in ActionScript. Then you’ll know which encoding ActionScript uses.