# Encrypt-then-authenticate variant used in IPsec

I am trying to understand the variant of Encrypt-then-Authenticate (EtA) that is used in IPsec. For this I have looked at this chapter.

What I got so far is that the integrity and confidentiality computations cover different parts of the EPS packet. What I don't understand is what exactly is done and how this is different from the general EtA composition (i.e. what is modified in comparison to the general EtA composition).

• What do you consider a "general EtA composition"? EtA, in my understanding, describes the order of operations and isn't a protocol description (how the encryption/authentication is performed). – Maarten Bodewes Jan 3 '16 at 12:17
• Yes, I agree. I meant the combination of an encryption scheme and MAC in an EtA fashion. – Lemon Jan 4 '16 at 6:28