Convert.FromBase64String from JScript on Internet Explorer

[Andy]

Hi, I have a MS Word binary data file that is sent from my .NET
webservice in response to an XMLHTTP request from an Internet Explorer
client. This data has to be base64 encoded to tunnel through a
firewall.

I've used the .NET Convert.ToBase64String() method to encode the
data. I understand that the Convert.FromBase64String only runs on the
server. How can I decode the data using jscript that's running on
the browser?

I've tried several RFC based algorithms written in JScript that seem
to only decode the text portions of the data. They seem to fail
decoding the binary parts of the file. When I open the file in Word,
the file conversion wizard pops up, although when I scroll through the
file all the text portions of it seem to be intact.

Does anyone know the algorithm used by
Convert.ToBase64String/Convert.FromBase64String so that I can emulate
the decoding it uses on the internet explorer side?

Andy