The source code shown below is really a combination of four different files. Start.asp and End.asp are examples. The Encryption.asp does all of the encrypting/decrypting work, which KeyGen.asp needs only to be run once, to generate the initial key. (For more information, be sure to read Encryption with ASP.
START.ASP
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<%@ LANGUAGE="VBSCRIPT" %>
<% Response.Buffer = "True" %>

<!--#INCLUDE VIRTUAL="/4Guys/Encryption.asp"-->

<%

'set up our querystring variables to pass to the next file
Script_Language = "Active Server Pages"
Nomination_1 = "4GuysFromRolla.com"
Nomination_2 = "FreeURL.com"

'set up the querystring
Encryption_String = "?SL=" & Script_Language & "&N1=" & Nomination_1 & "&N2=" & Nomination_2

'get key
Encryption_Key = mid(ReadKeyFromFile(Encryption_KeyLocation),1,Len(Encryption_String))

'encrypt the querystring and create new format
ENCRYPTED_CYPHERTEXT = "crypt=" & EnCrypt(Encryption_String)

'Redirect to next page with syntax [page.asp?crypt=youcantseeme]
Response.Redirect "end.asp?" & ENCRYPTED_CYPHERTEXT

%>
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END.ASP
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<%@ LANGUAGE="VBSCRIPT" %>
<% Response.Buffer = "True" %>

<!--#INCLUDE VIRTUAL="/4Guys/Encryption.asp"-->

<%

'retrieve out encrypted querystring info - replace Request.QueryString with request_equerystring
Script_Language = request_equerystring("SL")
Nomination_1 = request_equerystring("N1")
Nomination_2 = request_equerystring("N2")

Response.Write "The Y2K award for top scripting language goes to " & Script_Language & "<br><br>"
Response.Write "The nominations for cool website are: -<br><br>"
Response.Write Nomination_1 & ", " & Nomination_2
%>
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ENCRYPTION.ASP
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<% 
Dim Encryption_Key, Encryption_KeyLocation, DECRYPTED_CYPHERTEXT, g_CryptThis

Encryption_KeyLocation = "c:\emmanoble\4Guys\key.txt"

g_CryptThis = request.querystring("crypt")
Encryption_Key = mid(ReadKeyFromFile(Encryption_KeyLocation),1,Len(g_CryptThis))

If Len(g_CryptThis) > 1 then
	DECRYPTED_CYPHERTEXT = DeCrypt(g_CryptThis)
End If

Function request_equerystring(GetQueryString)

    Dim i,Found_It,Chop_DECRYPTED_CYPHERTEXT,Found_It_Here, TrimExcess
    Found_It_Here = 0
    TrimExcess = 0
    Chop_DECRYPTED_CYPHERTEXT = ""

    for i = 0 to Len(GetQueryString)
	Found_It = InStr(1, DECRYPTED_CYPHERTEXT, "&" & GetQueryString & "=", 1)
	If CInt(Found_It) > 0 then
		Found_It_Here = Found_It
		TrimExcess = 1
	End If

	If Found_It_Here < 1 then
		Found_It = InStr(1, DECRYPTED_CYPHERTEXT, "?" & GetQueryString & "=", 1)
		If (CInt(Found_It) > 0) then
			Found_It_Here = Found_It
			TrimExcess = 2
		End If
	End If

	if Found_It_Here > 0 then
		Chop_DECRYPTED_CYPHERTEXT = Right(DECRYPTED_CYPHERTEXT,(Len(DECRYPTED_CYPHERTEXT))-Found_It-Len(GetQueryString)-TrimExcess)
		Found_It = InStr(1, Chop_DECRYPTED_CYPHERTEXT, "&", 1)
		if CInt(Found_It) > 0 then
			Chop_DECRYPTED_CYPHERTEXT = Left(Chop_DECRYPTED_CYPHERTEXT,Found_It-1)
		End If
	End If

    Next

   request_equerystring = Chop_DECRYPTED_CYPHERTEXT

End Function




Function EnCrypt(strCryptThis)

	strCryptThis = ChkString(strCryptThis)

   Dim strChar, iKeyChar, iStringChar, i
   for i = 1 to Len(strCryptThis)
      iKeyChar = Asc(mid(Encryption_Key,i,1))
      iStringChar = Asc(mid(strCryptThis,i,1))
      iCryptChar = iStringChar + iKeyChar

	If iCryptChar > 255 then
		iCryptChar = iCryptChar - 256
	End If

      'iCryptChar = iKeyChar Xor iStringChar
      strEncrypted =  strEncrypted & Chr(iCryptChar)
   next
   EnCrypt = Server.URLEncode(strEncrypted)
End Function





Function DeCrypt(strEncrypted)

    Dim strChar, iKeyChar, iStringChar, i, iDeCryptChar

   for i = 1 to Len(strEncrypted)
      iKeyChar = (Asc(mid(Encryption_Key,i,1)))
      iStringChar = Asc(mid(strEncrypted,i,1))
      iDeCryptChar = iStringChar - iKeyChar
      'iDeCryptChar = iKeyChar Xor iStringChar

If iDeCryptChar < 0  then
	iDeCryptChar = iDeCryptChar + 256
End If

	If (iDeCryptChar = 34) or (iDeCryptChar = 39) then
	      Response.write "We detected a possible encryption ERROR<br>"
	      Response.write "please contact webmaster@LasVeg.as?subject=Encryption Error:" & g_CryptThis & "<br>"
	      Response.end
	Else
	      strDecrypted =  strDecrypted & Chr(iDeCryptChar)
	End If
   next
   DeCrypt = strDecrypted
End Function

Function ReadKeyFromFile(strFileName)
   Dim keyFile, fso, f
   set fso = Server.CreateObject("Scripting.FileSystemObject") 
   set f = fso.GetFile(strFileName) 
   set ts = f.OpenAsTextStream(1, -2)

   Do While not ts.AtEndOfStream
     keyFile = keyFile & ts.ReadLine
   Loop 

   ReadKeyFromFile =  keyFile
End Function


Function ChkString(string)
	If string = "" then 
		string = " "
	End If
	 ChkString = Replace(string, """", "")
	 ChkString = Replace(ChkString, "'", "")
End Function

%> 
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KEYGEN.ASP
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<% 

Const g_KeyLocation = "C:\emmanoble\4Guys\key.txt"
Const g_KeyLen = 512

On Error Resume Next

Call WriteKeyToFile(KeyGeN(g_KeyLen),g_KeyLocation)

if Err <> 0 Then
   Response.Write "ERROR GENERATING KEY." & "<P>"
   Response.Write Err.Number & "<BR>"
   Response.Write Err.Description & "<BR>"  
Else
   Response.Write "KEY SUCCESSFULLY GENERATED."
End If

Sub WriteKeyToFile(MyKeyString,strFileName)
   Dim keyFile, fso
   set fso = Server.CreateObject("scripting.FileSystemObject") 
   set keyFile = fso.CreateTextFile(strFileName, true) 
   keyFile.WriteLine(MyKeyString)
   keyFile.Close
End Sub

Function KeyGeN(iKeyLength)
Dim k, iCount, strMyKey
   lowerbound = 35
   upperbound = 96
   Randomize
   for i = 1 to iKeyLength
      s = 255
      k = Int(((upperbound - lowerbound) + 1) * Rnd + lowerbound)
      strMyKey =  strMyKey & Chr(k) & ""
   next
   KeyGeN = strMyKey
End Function

%> 
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