Hello everyone,
I've just released VisualBTC, an Android-based offline Bitcoin wallet that uses animated QR codes to send/receive transactions and synchronize with the Bitcoin network.
A quick YouTube video demo is available at
http://www.youtube.com/watch?v=m9-mbb0qc9I .
The idea is very simple: use a cheap 4.3 inch Android tablet with a capacitive screen ($50 in singles, bought from Amazon UK -
http://www.amazon.co.uk/gp/product/B009HY6BXU/ref=as_li_qf_sp_asin_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=B009HY6BXU&linkCode=as2&tag=ver02-21), disable its WiFi connection and transfer data only over animated QR codes (that is split any long strings into smaller chunks and animate those chunks as separate QR codes).
The application communicates with an HTML5 + JavaScript page that requires no server side components (QR code scanning and generation is all done in JavaScript, webcam interaction is also done locally via getUserMedia(), blockchain data is read and transactions are posted via blockchain.info directly from the page via JavaScript. It works with Chrome, Firefox and Opera. It
does not work with Internet Explorer, sorry, at least not yet.
The private keys never leave the tablet and it has no Internet connectivity whatsoever, so it cannot be attacked from the Internet.
The wallet application itself has been designed to be extremely simple, something even your grandma would be able to use. It only has two buttons: Pay and Sync.
Clicking Pay allows you to scan a QR code (standard format, bitcoin:address?...), then assembles a transaction, signs it, then shows an animated QR code with the transaction data. Showing that animated QR code to the webcam at
http://www.visualbtc.com/ posts the transaction to the Bitcoin network.
Clicking Sync shows a QR code that you once again scan at
http://www.visualbtc.com/ . It then shows you an animated QR code of your unspent outputs. You scan that with your wallet and it updates the balance and the internal list of unspent outputs.
Private key export/import is available using a special "Advanced mode" (hint: click 10 times in quick sequence on the QR code on the main page
).
This first release is free but is currently limited to 1 BTC maximum wallet value and 0.1 BTC per transaction. You can remove this limitation by paying (from the VisualBTC wallet itself) 0.25 BTC to us. You can also send donations and tips to
1VBTCXXcYmUCzYUcmdcakSGdyavUnByFF.
You can test this on any Android phone or tablet with a camera or you can buy that Pocket Scroll tablet I suggested above (full disclosure: it's an affiliate link, we get some $2.5 for each purchase
) - for $50 it's a great little device, 5-point capacitive screen, camera, WiFi, etc.
Suggestions and questions are very welcome! It's an early release and we do plan to improve it, but I wanted to get some feedback first.
Enjoy!
Razvan