A modem has nothing to do with encryption. It's merely turning digital signals into analogue and vice versa.
Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.
My broadband basic info/help site - www.robertos.me.uk. Domains, site and mail hosting - Tsohost.
Connection - AAISP Home::1 80/20. Sync 65258/14193Kbps @ 600m. BQMs - IPv4 & IPv6
As I recall BT Wholesale mandate CHAP. No idea what Vodafone use. In theory as they aren't using a wholesale provider, but are one themselves they have no need to use anything.