Using the **SNI extension** discussed above, the TLS Termination Proxy would check which of the TLS (HTTPS) certificates available it should use for this connection, using the one that matches the domain expected by the client.

In this case, it would use the certificate for `someapp.example.com`.

<img src="/img/deployment/https/https03.svg">

    And be compatible with all of them at the same time.

Create a utility function to hash a password coming from the user.

And another utility to verify if a received password matches the hash stored.

And another one to authenticate and return a user.

=== "Python 3.10+"

    ```Python hl_lines="7  48  55-56  59-60  69-75"
    {!> ../../../docs_src/security/tutorial004_an_py310.py!}

<img src="/img/tutorial/dependencies/image01.png">

## Simple usage

If you look at it, *path operation functions* are declared to be used whenever a *path* and *operation* matches, and then **FastAPI** takes care of calling the function with the correct parameters, extracting the data from the request.

Actually, all (or most) of the web frameworks work in this same way.