I just bought a Raspberry Pi and I am wanting to route an ad hoc wireless network interface fully through an SSH tunnel that was created using another wireless interface. I want to do this so that I can have a secured and private connection to the internet at places with public WiFi. I know this would be easier to do all on one computer, but I would like to have it on the RPi too since I use it for other network related things when I am using the internet, and then just simply connect to the ad hoc network from my laptop/phone. This will really help me with my iPhone because it does not support an SSH tunnel locally. How should I go about doing this? Thanks in advance for all of your help.
What he's saying is that SSH "now" (the past several years) supports a poor-man's VPN. That being said, may I strongly recommend a different solution? Either way, the learning curve is relatively steep, but if you want secured communications with a solid community, oodles of documentation, and clients that run on just about everything (Windows, Linux, Mac, iPhone, Android... you get the idea), you should check out OpenVPN. See http://openvpn.net/index.php/open-source/documentation/howto.html for lots of good getting-started info, and feel free to subscribe to the (very helpful) mailing list. Unsurprisingly, there's also an OpenVPN-on-Raspberry-Pi tutorial: http://raspberrypihelp.net/tutorials/1-openvpn-server-tutorial .
Lastly, one quick plug: OpenVPN is also crazy robust; unlike, say, my company's Cisco IPSec implementation (or SSH), OpenVPN is very good at seamlessly re-establishing a connection, which is handy for things like phones that wander in and out of connectivity.
I realize this doesn't technically answer your question, but as a long-time IT guy, sometimes it's more important to figure out what the person is trying to accomplish than take a literalist approach to a question.