How to implement aes{128,256)-gcm at openssh.com.

[Stef Bon]

Hi,

I want to implement the aes{128,256}-gcm at openssh.com ciphers in my application,
can someone describe how to do that?

First part is simple, these ciphers are aes ciphers, with 128 and 256 keys resp.
Second step is harder, the gcm mode, and howto deal with the AEAD, the
use of a nonce.
Is it like creating the cipher iv using the nonce mentioned in
https://datatracker.ietf.org/doc/html/rfc5116

Thanks in advance,

Stef

BTW earlier I've implemented the chacha20-poly1305 at openssh.com (also
with help from here).
It's also using an iv which is constructed using the sequence counter.