What is the difference between "Authentisierung" and "Authentifizierung"?
Authentisierung is the act of proving one's own identity; Authentifizierung is the act of verifying a claimed identity. The user authenticates (authentisiert sich) towards the server, and the server verifies (authentifiziert) the user.
* One exchange, two verbs: the subject authentisiert sich, the verifier authentifiziert. *
English uses one word, "authentication", for both directions, which hides a useful distinction:
| Term | Who does it | What it is |
|---|---|---|
| Authentisierung | The subject (user) | Presenting proof of identity: typing the password, tapping the token |
| Authentifizierung | The verifying party (server, IdP) | Checking that proof against the stored credentials |
Both are halves of a single exchange, which is why in everyday speech the terms are used interchangeably. In precise writing, though, "the server authentisiert" would be wrong: the server does not prove anything, it verifies.
Tip: Authentisierung, self: I show who I am. Authentifizierung, verify: they check it.
Go deeper:
Authentifizierung (Wikipedia, German) — the German article that spells out Authentisierung, Authentifizierung and Authentifikation.