> They are long, not easy to pronounce, sound too similar, have the first 4 and last 5 characters the same, they mean wildly different things and yet get interchangeably used as "authn".
This is a complaint about the English language. We still use many English words that are confusing. The computer science department is perhaps not the best place to reform an entire human language.
"AuthN" is shorthand for authe N tication.
"AuthZ" is shorthand for authori Z ation.
"AuthN+Z" is shorthand for something that provides both.
> If i give you keys to a room with the number 101 on it, is that authentication or authorization, or none ?
Authorization.
To authenticate is to prove who you are. To authorize is to grant access. The key does not prove who you are, it proves you have access to the room.
> If a gatekeeper says "sorry, invalid auth", what the f does that even mean?
Means either authentication or authorization or both failed. This is a complaint about a stupid programmer who can't communicate properly, not with a word.
Bet you a million dollars they'll output the error "invalid login" when it's actually a permissions issue (user can't log into this site/tenant/group/resource, not because the username or password was wrong, but because they didn't have the right role assigned). Changing the word won't make the programmer make fewer mistakes.
> An expired token, is that authentication failure or authorization error?
Authentication.
'Tokens' are not one thing (many things can be called 'a token' and be used in different ways... again, choose the right term to communicate properly), but generally speaking, 'tokens' are things you use to authenticate your identity, and the backend system matches the authenticated token with the authorized roles.
> What about fake token ? A token with valid signature but wrong audience ?
Authentication. Authentication and/or authorization (depends how your example works).
> Its such a fu*ing mess.
The concepts can be difficult to understand at first. Use them more and they make more sense.