Topic: Using old smartphone as cold storage, signed transaction => QRcode (Read 1251 times)

I see, thank you. I might buy a Trezor (not available in this country), besides trying the cyanogenmod thing on my LG P500 one of these days.


Thank you, I do have a more recent smartphone, the idea was to use the old one - keeping it offline - just as a cold storage (*) and the more recent one as the watch-only part, and have the two communicate through QRcode/camera.

(*) I might also keep as a "colder" storage the wallet I generated after booting - ethernet cable unplugged - a live DVD Linux distro coming with Electrum, and transfer to the wallet I'd also have on the old smarphone just what I think I might need to spend while away from my PC.

i would give suggestion for you to buy new smartphone at middle range which is support with bitcoin wallet and don't install any apps on that smartphone and don't forget to install antivirus. you only use that smartphone for saving your bitcoin and send it to other wallet and not make any transaction wallet which you don't own it.

Sure, with the 24 word seed you can recover your private keys without using the trezor. I had to do this lately to transfer some coins which I bought in an ICO. 

Wow nice, THANK YOU, I'm downloading all those buiilds, opened the wiki and will read docs (never rooted/flashed a smartphone) and will definitely give it a try (although "no recovery" sounds to me like in case I brick the phone it might be difficult or impossible to revive it).


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What I did a couple of days ago: get Tails on my PC (*), unplug the ethernet cable, burn to DVD, boot it while still offline, use that Electrum version to generate the wallet and store it on a pendrive which will never go online + write seed on paper + export public key on another pendrive, than install Electrum on my Android phone from Google Play and import the public key. BUT of course this is watch-only and requires to sign outgoing transactions from a PC offline after booting Tails and opening the cold storage wallet from pendrive or typing in the seed phrase.

(*) Tails: not for the amnesia feature nor Tor, just as a pre-made live CD already coming with Electrum, assuming I'd use it offline

What I had done a couple of years ago, although I never used that wallet, was to choose Linux Slax instead, modify it by adding the latest Electrum, burn it and boot from it while offline, generate the wallet and save it on pendrive + seed on paper, then I'd use the watch-only version from Slax or some other Linux distribution or Windows.


WITH YOUR SUGGESTION I might be able to sign outgoing transactions with no need to have a PC handy, by simply using my old (and smaller) smartphone offline.


What I like about Electrum is that being the cold storage offline it should be 100% sure, right?... Or is the deterministic nature of the seed-to-wallet passage vulnerable to some kind of smart attack?
Do any other wallets offer the seed phrase feature?


I saw reviews of hardware wallets: Ledger needs Google Chrome, ruled out for me I have been trusting Google more than enough and recent international events are making me feel like migrate to some other e-mail account and not buy another Android phone ever (I already set DuckDuckGo as my default search engine on any OS and browser I use). Besides, the Ledger has no display => pin not so safe, a review said.

Trezor: better. BUT I wonder if it allows a seed phrase to restore the wallet elsewhere in case something happens to the hardware (e.g. stolen with other stuff).

The latest Electrum app requires gingerbread (android 2.3), so it should run on that build, try it!

Thank you, yes I'd have the seed phrase noted on paper of course, I could always restore the wallet elsewhere.
The old phone is an LG P500, I use it every day as audio player via blutooth. (The one I currently use as phone has of course a much better hardware, and it came with Android Lollipop.)

I'd install Electrum and with the old phone I'd go offline forever (delete Wifi and APN settings... I don't think I even have a SIM chip in it at the moment), Then I'd use it as cold storage.

(I would be more worried about users reporting that Electrum went stuck while broadcasting a transaction, some even waited for a few days, I wonder how one should behave in such case, somebody commented that it's not uncommon.)




Thank you. However, builds for that device are 3-4 years old: http://download.cyanogenmod.org/?device=p500
I doubt I would be able to install the most recent version of Electrum.



Thank you, that would be one more reason to choose a wallet which permits to restore from a seed phrase. Which ones do that beside Electrum?



Thank you. Problem: the last thing I bought from ebay a couple of months a go never arrived... I'm in Argentina at the moment, I might buy a hardware wallet the first time I travel abroad.
Do they work via wifi too or do I always need to connect one of those via USB to a broadcaster app? And that would be Electrum or Mycelium or...?
(The two phones thing with QRcodes sounds very safe to me anyway, no chance any kind of super smartly coded virus could do anything, no USB or Blutooth or Wifi connection to the cold storage. I guess hardware wallets must be very safe anyway, and maybe the USB thing is as fast as QRcode scansion.)

Do hardware wallets offer any chance to restore from a seed phrase in case you loose the hardware or it gets stolen?



I had read of some kind of keys being accepted by Mycelium as well as Electrum (and some hardware wallets being compatible to various software walltes) but I'd actually be happy to avoid making strange mixes, thanks!

bitcoin clients aren't mutually compatible so give up on the idea of using different clients on your PC and phone and trying to get them to share the same wallet. i'm not saying it can't be done. it's just not something a newbie should be trying.

if you want a single wallet that will work on multiple types of devices then i suggest copay.

Why bother when you can buy a Ledger Nano S for $60 and know your bitcoin are secure.

This would work but I would be concerned with using an old phone, I have had previous phones which refused to start up and I lost all my data, there is always a chance of something like that happening.

I recommend that you have a look at the cyanogen android firmware. This is available for a lot of android models and gives you a more current android os version, so you can run more of the recent apps!

http://www.cyanogenmod.org/

I would be careful with using an old smartphone. Their hardware may fail at any time or your OS may get stuck in a bootloop. Atleast make sure you have proper back-ups of the wallet.

I guess your idea would work well though. The scans are very easy to use then. I think it would be best to do a full hard reset of the phone data, download the app and then go offline for ever.

Hi, I'm a BTC newbie.


I'd like to use my old smartphone as cold storage, download Electrum, disable WiFi and data connection "forever", use it to sign payments and send the signed transaction to my current smartphone running a watching-only instance of Electrum, through QRCode on screen => camera, which seems to me even safer than passing files between computers through a USB pendrive.

Is it doable or is it a new idea / feature request / suggestion?

Actually, at present no Electrum version is available on Google Play Store for an Android 2.2 phone. Maybe a cold storage only version _could_ be made available for older Android versions, recommending to cut any communications before generating the wallet (which generation would _not_ have to rely on old faulty java pseudo-random generators of course).

On Google Play Store there's an app called "Paper Wallet" which works on Android 2.2, BUT 1) It sends _keys_ through QRcode, not signed transactions 2) Mycelium doesn't seem to be able to scan those QRcodes (I haven't tried with Electrum yet... besides I haven't deeply tested Paper Wallet and I'm not even sure it does save a wallet or just generates one for you to write down stuff).


Thank you.