Parse form values before sending to options.php

I'm developing a custom plugin, which requires input of authentication data for a remote API, and this data needs to be saved. I want to encrypt it before saving to db.

I've added a settings page, containing:

form method="post" action="options.php"
  !-- form fields here... --
/form

Rather than having each option saved as a different entry in {wp_table_prefix}_options table, I want them saved as an object in only one row, so the name attributes are of this type:

input name="plugin-slug[option-key]" ... 

The question is fairly simple: what is the proper way to encrypt the data before saving it in db? I'd like to hash the entire object and I'm going to decrypt it back after get_option('plugin-slug').

Is there a default method to filter the sent request to options.php, before saving it in db? I haven't been able to find anything on the topic or an example that already does it. It's hard to believe nobody needed something similar before.

I also tried finding a filter or action called inside into options.php but, as you can see, it has a fairly convoluted logic and some backwards compatibility code... I was hoping there's a more straight-forward way of doing it than pinning toothpicks into options.php.