you need to include inc_sha256.asp and inc_func_common.asp (instead of inc_functions.asp). Other than that your old files could stay the same.
As I said in another topic about external login/logout:
In inc_header.asp this part can be found:
select case Request.Form("Method_Type")
case "login"
strEncodedPassword = sha256("" & Request.Form("Password"))
select case chkUser(strDBNTFUserName, strEncodedPassword,-1)
case 1, 2, 3, 4
Call DoCookies(Request.Form("SavePassword"))
strLoginStatus = 1
case else
strLoginStatus = 0
end select
case "logout"
Call ClearCookies()
end select
You need to include that on every page where you show the login fields, above the <html> tag. That way the password will be encrypted. At least, it should be.