Environment - PHP extension sodium
The php-sodium extension provides strong encryption capabilities in an easy and consistent way.
Note that, for sites not having the extension installed, a php-openssl based solution, considered suboptimal, is used, and this fallback will stop working in a few versions (Moodle 4.2). See MDL-71421 for more details.
Hence, it's highly recommended to start using php-sodium.
See also https://www.php.net/manual/book.sodium.php and https://py-ipv8.readthedocs.io/en/latest/preliminaries/install_libsodium/