Executing User Defined Function via Classic ASP Function - encryption

Question

OK, I am trying to write a Classic ASP function that will call a SQL function and return the output.
I am trying to use a paramaterized ADODB connection but I don't quite know how these work. Trying to learn the correct way.
The SQL function just takes two string input where one is a "salt" and the other the actual text and turnes it into a hex.
Works fine in SQL but I just can not get it to work through classic ASP.
I keep getting,
ADODB.Command error '800a0cc1'
Item cannot be found in the collection corresponding to the requested name or ordinal.
Sub Encrypt(plainString)
strSQL = "SET NOCOUNT ON;SELECT dbo.Encrypt('xx', '?') as keycode"
Set cnnEncrypt = Server.CreateObject("ADODB.Connection")
cnnEncrypt.open CONNSTRING
Dim cmd1
Set cmd1 = Server.CreateObject("ADODB.Command")
cmd1.ActiveConnection = cnnEncrypt
cmd1.CommandText = strSQL
cmd1.CommandType = adCmdText
cmd1.Parameters(0) = plainString (**Original Error Occured Here!!!!**)
Set rsEncrypt = cmd1.Execute()
If not rsEncrypt.EOF Then
Encrypt = rsEncrypt.Fields("keycode").Value
Else
Encrypt = "blank"
End If
' Clean Up
rsEncrypt.Close
Set rsEncrypt = Nothing
cnnEncrypt.Close
Set cnnEncrypt = Nothing
End Sub
New Working Version after reviewing "Cheran Shunmugavel" answer.
Calling on site like this
< % Response.Write Decrypt(Encrypt("test")) % >
You can't print the Encrypted code to the page because it is Binary. You would need a Binary to String function.
I converted from Sub to Function because I wanted the function to return a value.
Function Encrypt(byVal plainString)
strSQL = "SET NOCOUNT ON;SELECT dbo.Encrypt('xx', ?) as keycode"
Set cnnEncrypt = Server.CreateObject("ADODB.Connection")
cnnEncrypt.open CONNSTRING
Dim cmd1
Set cmd1 = Server.CreateObject("ADODB.Command")
cmd1.ActiveConnection = cnnEncrypt
cmd1.CommandText = strSQL
cmd1.CommandType = adCmdText
cmd1.Parameters.Append cmd1.CreateParameter("", adVarChar, adParamInput, Len(plainString)+1, plainString)
Set rsEncrypt = cmd1.Execute()
If not rsEncrypt.EOF Then
Encrypt = rsEncrypt.Fields("keycode").Value
Else
Encrypt = "blank"
End If
' Clean Up
rsEncrypt.Close
Set rsEncrypt = Nothing
cnnEncrypt.Close
Set cnnEncrypt = Nothing
End Function
And here is the decrypt function.
Function Decrypt(byVal plainString)
strSQL = "SET NOCOUNT ON;SELECT dbo.Decrypt('xx', ?) as keycode"
Set cnnDecrypt = Server.CreateObject("ADODB.Connection")
cnnDecrypt.open CONNSTRING
Dim cmd1
Set cmd1 = Server.CreateObject("ADODB.Command")
cmd1.ActiveConnection = cnnDecrypt
cmd1.CommandText = strSQL
cmd1.CommandType = adCmdText
cmd1.Parameters.Append cmd1.CreateParameter("", adVarBinary, adParamInput, LenB(plainString)+1, plainString)
Set rsDecrypt = cmd1.Execute()
If not rsDecrypt.EOF Then
Decrypt = rsDecrypt.Fields("keycode").Value
Else
Decrypt = "blank"
End If
' Clean Up
rsDecrypt.Close
Set rsDecrypt = Nothing
cnnDecrypt.Close
Set cnnDecrypt = Nothing
End Function

Answer 1

First off, you don't need delimiters around the parameter placeholder. SQL Server will handle it appropriately.
strSQL = "SET NOCOUNT ON;SELECT dbo.Encrypt('xx', ?) as keycode"
Secondly, the Parameters collection is initially empty and must be populated before you try to access it (i.e., the line cmd1.Parameters(0) = plainString). There are several ways of doing this, but I prefer creating the parameters manually using the CreateParameter method:
cmd1.Parameters.Append cmd1.CreateParameter("", adVarChar, adParamInput, Len(plainString), plainString)
Also, it's not apparent from your code, but make sure you've got the ADO constants defined, either by referencing the type library, or by including adovbs.inc.