Bitcoin Forum

Hi! I've just updated my android offline "paper bitcoin client" - https://play.google.com/store/apps/details?id=ru.valle.btc

Now it can not only to generate key-address pair, but also it can create and sign transactions using your private key, so now you can quite easily spend money from your paper wallet. Mini, brain wallet, WIF, WIF-compressed, BIP 38(both ec modes) private key formats are supported. Enjoy!

sources: https://github.com/ValleZ/Paper-Wallet

NEW in version 2.2.0 - wallets printing, view QR codes and changing password for encrypted keys

ps Check out the app's permissions ;-)

What are the list of spending fees?

how exactly are you able to spend money sent to this address?

Now it is hardcoded to 0.0005 btc, next version will allow to set this fee.

Any address with positive balance have unspent outputs (transactions). You have to obtain these transactions in raw form from bitcoin qt and paste it to the app. Then it would generate spending transaction (and verify it by itself) and after that you have to copy it and push it to bitcoin network by yourself using bitcoin qt or any other bitcoin service which allow to do that. It's quite easy. Most complicated thing is to obtain that unspent raw transaction.

Sources published: https://github.com/ValleZ/Paper-Wallet

key generated by the paper wallet are insecure due to the android bug. http://bitcoin.org/en/alert/2013-08-11-android
see https://github.com/ValleZ/Paper-Wallet/blob/master/src/ru/valle/btc/BTCUtils.java#L53

please notify all users of the software that keys generated by this need to be switched.

Fix is already available, warning posted. Thanks for the reminder!

I've added some new great stuff like BIP 38 encoding/decoding, qr code scanner, retrieving unspent transactions from blockchain.info (by copypasting from browser) and more!

Good!

Can you also add brainwallet functionality? (ex: com.CIMS.BitcoinAddress (https://play.google.com/store/apps/details?id=com.CIMS.BitcoinAddress) isn't updated anymore)

Yes, it was implemented too :-) Try to type anything in private key field

This is a pretty nifty app, good work.

Thanks!

New version available with lots of new features like printing, qr codes, sharing, simplified UI, and more

When you will release new version? As I do like this one but looking forward to try new one

I don't know, maybe in ~2 weeks. I'm slowly updating tx generation part.

What is offline paper wallet? How it works?

Nice app will test this

It's just a bitcoin wallet without permission to use internet. It also doesn't store any information what you don't see on screen, so you have to keep your "wallet" (private keys) somewhere else, for example - in a written form on a paper.


joethejudge77:

Sorry, I'm working on automatic fee calculation and it have more obstacles than I thought. I need to design new UI elements for entering confirmations count and test it very carefully, so release will be a bit later.

Version 2.30 is out. There are automatic fee calculation and better UX.

Good ;D

I just noticed that the latest version supports printing for Android 4.4 (KitKat). How does that work? Is there a way to hook up USB printers to such Android devices and print them with this?

Looks good, nice work.
Can private key be stolen from printer if not spent first?

I don't think it is possible though you can print through WIFI, probably a bad idea if you are really concerned about security! ::)

   ~~MZ~~

Precisely. USB would be my only possible consideration.

Sorry, my bad! Actually, I think you can but I haven't tested it. Download app(https://play.google.com/store/apps/details?id=com.dynamixsoftware.printershare&hl=en) and try to print. Please give a feedback, so others can also try it. :) Sprry once again! :)

  ~~MZ~~

I would definitely test it, but I don't have a KitKat device.

I refreshed this project few days ago to make it look bit better on tablets and new devices, fixed the only crash and updated hash algorithm from SHA-1 to SHA-256 in random number generator.