UFN_GET_MAC_FOR_TEXT

                create function [dbo].[UFN_GET_MAC_FOR_TEXT]
                (
                    @PLAINTEXT nvarchar(4000),
                    @TABLENAME sysname
                )
                returns varbinary(24)
                with execute as owner
                as
                    begin 
                        -- NOTE:  The symmetric key sym_BBInfinity must be opened prior to calling this function. 

                        declare @TABLEID int;
                        declare @RETVAL varbinary(24);
                        declare @KEY varbinary(100);

                        select @TABLEID = object_id(@TABLENAME);
                        if @TABLEID is null
                            return null;

                        SET @RETVAL = null;
                        SET @KEY = null;

                        select 
                            @KEY = DecryptByKey(MSGAUTHCODE)
                        from
                            dbo.MACINDEXKEY
                        where
                            ID = @TABLEID;

                        if @KEY is not null
                            select @RETVAL = hashbytes(N'SHA1', convert(varbinary(8000), @PLAINTEXT) + @KEY);

                        return @RETVAL;
                    end