Environment - PHP extension sodium

The php-sodium extension provides strong encryption capabilities in an easy and consistent way. This extension is required from Moodle 4.2.

Note that it is still highly recommended to use php-sodium in Moodle 3.11, 4.0 and 4.1, which also support the extension. Sites which do not have this extension installed use a php-openssl based solution as a fallback, which is considered sub-optimal. See MDL-71421 for more details.

See also https://www.php.net/manual/book.sodium.php and https://py-ipv8.readthedocs.io/en/latest/preliminaries/install_libsodium/