what is auth data in AES-GCM I am trying to understand AES-GCM and I do not understand what I should transmit to Auth Data during encryption. What kind of data is that?
The relationship between Auth Data and Plaintext can be compared with that of a network packet header and payload. Modern ciphers provide provision to &quot;authenticate&quot; additional data that's not encrypted so that more robust protocols can be designed. Of course, if you don't have header, you can pass an empty bit string to it.