Manage bitcoin across multiple devices

The recent run up in the BTC/USD exchange rate has created a flurry of interest from newcomers, especially in the popular Reddit forums of /r/bitcoin and /r/bitcoinbeginners. One such person asked if their Bitcoin wallet had to be limited to just one device, since it is natural for one to want to access their funds no matter where they are, very much like an online bank account. While it is indeed possible to store your bitcoin on web wallets like Coinbase and have the ease and familiarity of online banking, most experienced Bitcoin “hodlers” recommend against having bitcoin savings out of your control, including myself. Therefore, I set out to describe some of the ways one can access locally generated wallets across multiple devices (PC/Mac and mobile), and you may be surprised by the possibilities!

1. The most capable way is to download a wallet like Copay to run on both mobile and desktop devices (alternatively, use Mycelium as the mobile app), then use the master seed from the first installation to “restore” a wallet on the second and subsequent installations. This will give you send and receive access across all devices, but also expand your risk profile to include any attack surface from any platform! Therefore, I don’t recommend this method and also why I don’t tend to recommend Blockchain.info and similar web-based solutions.
2. Next is to use multiple wallets but split your total bitcoin holdings between them. This requires backing up more than one wallet seed, but each is isolated from the other if one develops a problem. Tracking your total bitcoin holdings is harder this way. Some people use spreadsheets or other financial software to follow it all, especially if they have paper wallets also.
3. The third is to use one wallet on one device and import it’s xpub (extended public key) into another. Mycelium (on Android) can import Copay and Mycelium xpubs plus Trezor, Ledger, and KeepKey hardware wallets. Copay can import Copay wallet files plus Trezor and Ledger. Electrum (on desktop) can import Mycelium, Copay, Airbitz, and itself. Blockonomics.co (website) can import all of these. This is a method I am most fond of, and can be combined with either of the preceding methods for even more flexibility. Some examples are needed to understand this properly:

Example #1: Setup one full wallet on desktop using Copay and export that wallet without private keys to a Copay wallet on mobile. There you can track your balance and receive payments, but not be able to spend from the mobile wallet (any compromise of your receive-only wallet would leak your privacy, not your bitcoin).

Example #2: Setup a full Airbitz/Mycelium/Copay wallet on mobile, then export it’s xpub to an Electrum wallet on desktop (or Copay mobile to Copay desktop). Here you can track your balance and generate new addresses to receive funds on the desktop, but only be able to spend bitcoin from your mobile wallet. Since mobile operating environments are typically more secure than desktop equivalents, and because you can use bitcoin on the go with your phone, I would recommend this path. Mycelium can also track any paper wallets you have without needing the private key.

Example #3: Setup multiple full wallets on mobile, desktop, or paper and track them all separately and in aggregate via Blockonomics.co. Import each wallet’s xpub into your Wallet Watcher account at Blockonomics.co to see each balance (and total balance) and generate addresses for each, plus create quick hosted invoices off of those addresses. You can access Blockonomics from any web browser, but you can only spend with the full wallets on their own devices. Compromise of Blockonomics.co will only leak your privacy, not your bitcoin.

Blockonomics is a free and convenient service for those with multiple wallets (including paper wallets) to keep an eye on. Although it’s required to trust us somewhat with your privacy using a regular account, you can also choose to use Tor or a VPN and Blockonomics’ guest login to pseudo-anonymously track your total holdings (throw in random addresses you don’t control for extra obfuscation).

Warning: Be sure to test everything you setup with small amounts before choosing to rely on a particular solution! Some wallets are incompatible with others and may generate un-spendable addresses. Check to see that each xpub import shows the correct next address and balance. The pairings above are based on my own experience, but not guaranteed. Be sure to backup every full wallet you create!

Contact me at patrick@blockonomics.co if you need help with any of these solutions.

Patrick Patton - Business Development Manager, Blockonomics.co