On getting command line arguments not to show up in ps

Environment variables will show up in ps auxwwe

If you can modify the program, you probably want to use a pipe or a
file.

Some folks like to rewrite argv to not include the sensitive data, but
there's still a narrow race window with this approach, and it isn't
astonishingly portable, either.

Another possibility is to use another machine that doesn't have
untrusted users on it, or use some form of virtualization technology to
emulate having a dedicated machine (like VMWare, QEMU, Xen, Solaris'
Zones, FreeBSD Jails, &c).

If you can't modify the program, you probably should complain to the
vendor.