Ubuntu Security :: Using AutoFS To Mount CIFS Share Without Leaving Unencrypted Passwords

I followed this howto in order to mount CIFS shares on demand. This works great, however, this guide suggests leaving my network passwords unencrypted on the disk. This is a very bad security practice, as the passwords can be easly retrieved by booting the computer using a different OS.

I was looking for a way to secure things up, so I came up with this solution: Instead of storing the passwords plain text on the disk, I store them in a tar file encrypted using GPG. When I boot my system, I open this file to a directory in /dev/shm, and order AutoFS to retrieve the passwords from there.

This does the trick, but I presume this solution is not that secure, since /dev/shm content can be written to the swap partition. Is there any other solution which is a better security practice? Maybe using some sort of keyring service?