private key crypto on form post data

[ESPN Lover]

Hello,

I need to find a way to encode a form post element with a private key, which
then can be decoded using that same private key using ASP. Yeah, Yeah, I
know strange request. Is there some object on my IIS 6 server or some
object in the Win2000 OS that would allow me to pass in data and a key and
get back the encoded data as well as being able to pass in the encoded data
with the key and get back decoded data?

Would prefer to use a syntax like
DIM myData, X
myData = ...some routine to get data...
SET X = Server.CreateObject("COMPONENT.CLASS")
DIM enc
enc = X.Encode(myData, myKey)
SET X = Nothing
Response.Write "<INPUT Type=Hidden Name=EncodedStuff Value=" & enc & ">"
Then on form receipt
DIM myEncData, enc
myEncData= Request.Form("EncodedStuff")
SET X = Server.CreateObject("COMPONENT.CLASS")
DIM decoded
decoded= X.Decode(myEncData, myKey)
SET X = Nothing
do stuff with decoded data....
Thank you!