If you already know the checksum for some huge chunk of the message then you don't need to recompute it to append some data and get a new checksum (at least for

If you already know the checksum for some huge chunk of the message then you don't need to recompute it to append some data and get a new checksum (at least for CRC). On the read side you would want to have checksums at whatever granularity you want to be able to read but for a larger combined CRC checksum you don't need to ever reread data to append or prepend to it.