AEAD robustness implementation examples about libsodium-doc

[jedisct1]

A key identifier is anything that can let your application uniquely identify a key, in a protocol handling key rotation.

This information doesn't have to be secret nor unpredictable. It can be a serial number (even a simple counter) or a random value, although padding to at least 128 bit wouldn't be a bad idea.

If this is confusing, I'd rather remove this from the documentation, especially since papers have been published on that subject.

[samuel-lucas6]

That makes sense. I assumed it was referring to deriving some sort of subkey before.