Data integrity authentication scheme

Data integrity authentication scheme

I want to find out if there is a data integrity authentication scheme, like Message Authentication Code (MAC) that will help me authenticate the integrity of the data without attaching MAC to do data. I can intermingle the MAC in the data so that the data size doesn't change, but the data size must not change. Thanks in advance.


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Unfortunately, there's no good way to do what you want.

There are a number of ways do data integrity and authentication, but all the reliable ones require adding to the data. The addition can be of small fixed size, but you must add to the size of the data. There are, however, other schemes that allow data to shrink -- if your data is large enough, you could compress it and get back more than the size of the MAC. But this isn't guaranteed.


This was first published in April 2001