Topic: Idea: Offline portable wallet - page 2. (Read 3473 times)

But Armory's offline signing isn't standalone.


It still needs the connected instance to create the unsigned transaction which is than brought over to the offline system for signing.

And here's the reason you wouldn't want to trust the merchant to build the unsigned transaction for you:
 - https://bitcointalksearch.org/topic/m.1187718

I haven't looked at this closely but the approach is interesting

VisualBTC - Android-based hardware offline wallet using animated QR codes
 - https://bitcointalksearch.org/topic/ann-visualbtc-android-based-hardware-offline-wallet-using-animated-qr-codes-210371

you might beable to add to my thred https://bitcointalksearch.org/topic/ann-crd-credits-a-new-crypto-with-real-innovation-226582
i am open to ideas

First I'll explain the problem and then my proposed solution:
The problem is that if you want to go on holidays or somewhere where you don't have data connection in your cellphone (ey! I'm on holidays in Berlin http://tinyurl.com/bwg33vf and I want to use my bitcoins), it's not possible to pay in any shop where they accept Bitcoins because you can't broadcast the transaction from your cellphone.

Of course, you can access WiFi or pay the data-roaming cost but I imagine a much easier scenario for the end user by using the shop's Point of Sell to broadcast the transaction. Here is the explanation:
1. When paying, the user scans the QR code of the shop address where the payment has to be sent to
2. The user includes the amount to pay and signs the transaction in the phone (android/iphone/etc) wallet
3. Now the transaction gets converted into a transaction QR code in the user's phone -> Offline broadcasting
4. The shop seller can now scan the transaction QR code in the shop's POS which has to be connected to internet
5. The shop's POS broadcast the client's transaction and immediately verifies the payment


Remarks:
- Size of transaction: QR codes can't handle too much data (less than 3Kb according to http://www.qrcode.com/en/faq.html) but if the user were to use a specific address only for this offline portable wallet, like the physical wallet you take with you, the transaction size should be quite small as there is only one address to take the funds from and one to send funds to (usually).
- Security: The portable wallet should have it's own address and private key separated from the rest of the wallets, therefore, if the phone gets compromised/stolen, only one address with the day to day cash amount is lost.


This is very similar to what Armory is currently doing for offline wallets but the transference method through usb stick is not as simple as the QR code, specially in the mobile environment. I haven't seen this already implemented in any of the wallets but maybe I'm mistaken and some android wallet is already able to do this transference of offline transactions.


Let me know what you think of the idea and if there is any extra trouble you can think of.