Done that. It got his attention. The problem now is to keep his attention long enough for him to learn something. He came up with the bitcoin idea so I'm trying to seize the opportunity!

Almost. If the wallet isn't on the active machine, it can't be lost or stolen. Also the secure keys could be stored separately, perhaps scanned as qr codes or loaded as needed via usb port. The tablet is essentially a dumb terminal. SSH would be configured to accept connections to the wallet only from devices with specific uuids.
I send a request for x amount of bitcoins, get back a qr code, the merchant scans the code, transaction is done.

At least I think that is what I'm reading about spending bitcoins.

Thanks for the response,

Basically correct.

The Quads are running Udoobuntu, a Ubuntu for ARM processors. The Ellipsis' run Android (as does a NOOK I have available). The Ellipsis will be used only as a client (i.e. to make or receive payments). The Udoo will be doing mining and serve the wallets.  SSH between the Ellipsis and the Udoo will be over either the 4g or a local hotspot.

The Udoo has 4 cores for the ARM and the equivalent of an Arduino UNO on board. I also have available several Raspberry Pi's and other computers to play with.

I would like to build the Android bitcoin wallet and ssh apps from scratch.

That would work if I weren't so paranoid.
Things I do (and recommend to anyone where serious information or money is at risk):
a) Have at least one computer with no internet connection, and with only wired keyboard and mouse;
b) Build all apps that must be secure from source on the unconnected computer;
c) Create all keyrings on the unconnected computer;
d) Don't use an MS operating system for secure builds;
e) Transfer all data from the unconnected computer using only freshly partitioned and formatted media;
f) Only use media that has been subjected to a secure wipe.

BTW, don't use video card based mining hardware. Most video cards have been cracked. Some come from the factory with pre-installed viruses.
   

This post is a good candidate for RTFM comments. Identification the FM to read would be appreciated
On another post, I've asked about building a bitcoin miner using Udoo Quads. I'm sure that (eventually) that project can be setup to accept ssh logins in a secure manner. My provider is Verizon and I have a couple of ellipsis 7 tablets to use as remote clients. Having secured the server end, the problem is to secure the remote client. I can write Android apps and root the tablet if necessary. I do not trust the tablet or network to be secure.

Any help for the truly paranoid?

Thanks to all who responded to my previous post. Here is where I am now. Any comments, suggestions, or recommendations appreciated.

My grandson bought some ASIC mining hardware that he attached to his computer. But it has a noisy fan and gets in the way of his game playing. Also he keeps downloading viruses.
 To help him learn some security and computer science while supporting his mining interest.

My idea is to attach his hardware to a Udoo Quad which could be left running off in a corner somewhere. I need to learn a lot about bitcoin or he will get frustrated and give up. So far I've gotten bitcoin core to build and bitcoin-qt to run with the following results :
a) It uses all the RAM and an additional 750+ Mb swap;
b) It uses about 26% of one core;
c) It might work for managing one wallet, but is too slow for anything else.
d) Power consumption is minimal

The next step for me is to join the Udoo up with some mining hardware and get that running.  This go-around the hardware should be cheap, but good enough to keep the kid interested. He can spend his own money to buy expensive hardware

Any suggestions?

Probably not. Compression only works on files that have lots of redundancy. For example, source code files (C, Python, etc) have lots of redundancy because some symbols are more common than others. Executable files have less redundancy and cannot be compressed as well. To be effective, bitcoin dat files should have low redundancy. Encryption techniques also reduce redundancy in files because redundancy provides clues to an attacker.

The real solution might be to find some way to collapse the older transactions into some sort of archive so we newbes don't have to down load more than a couple of years to be productive. If the archives were distributed over the internet they would be available everywhere as needed.

Thanks for the link. Right now it is showing between 6hrs and 2days to down load!
Once it is downloaded what do I do with it? This is to be a multi-user system and so far bitcoin-qt wants to download a copy for each user. Is there someway (perhaps links?) to insure only one copy is used?

My grandson is trying to get started mining bitcoins using hardware attached to his gaming computer. He has no idea about security.
I've started a learning project by building bitcoin core 0.9.2 on a Udoo Quad with attached drive. My plan is to run as a GPU miner until he learns enough linux and security process', then get more hardware. Ultimately the Udoo would hide  behind the tv and run 24-7.

0.9.2 is very slow. It has been "synchronizing with the network" for 3 days now. CPU usage seems to average between 5% and 12%. It was built using the default setup.sh-configure-make-make install route.

Any idea why it is so slow?

Also any suggestions as to which hardware to use with the Udoo would be welcomed.