sq-autocrypt(1) on Linux
The text 4ba418919483, as Debian 11 (Bullseye) shipped it.
Communicates certificates using Autocrypt Autocrypt is a standard for mail user agents to provide convenient end-to-end encryption of emails. This subcommand provides a limited way to produce and consume headers that are used by Autocrypt to communicate certificates between clients. See https://autocrypt.org/