I was sent over a free pack of Opendime by Coinkite so I could put together this Opendime review (and the guide at the end).
What is an Opendime? How does an Opendime work, and how do you use it?
This is all covered in this Opendime review, with my hands-on impression and a quick tutorial which shows this nifty little Bitcoin (BTC) USB stick in action.
Advantages & Disadvantages
- Only about $13 / £11 per Opendime USB stick.
- Compatible with any computer, laptop, or phone (with a USB connection).
- Simple to setup and easy to use.
- Allows you to pass along Bitcoin (BTC) like cash (without on-chain transactions).
- Secure, with no access to the private key until an (obvious) seal is broken.
- You cannot backup any Bitcoin (BTC) stored on an Opendime.
- Opendime must be destroyed to spend any Bitcoin (BTC) stored on it.
- Not suitable for storing large amounts of Bitcoin (BTC).
What is an Opendime?
There’s nothing else like Coinkite’s Opendime ‘Bitcoin Stick’ which is available on the market.
The Opendime is a small USB stick which can be loaded up with Bitcoin (BTC) and passed on to others just like cash. That means it’s instant, no on-chain transaction is required, and there’s no trace that the transaction took place.
It’s a barebones device, but it is deceptively durable.
@OPENDIME after spending 1hr in the washing machine, tumbled at 900 rpm, dried at 60°C (140° FH) for another hr: works just fine.
— Bois_No2X ⚡️Permabull (@Bois_I) June 19, 2017
It is shipped in a small plastic sleeve and everything you need to get started with it is included in text files on every Opendime device, as well as an instruction card with each pack.
Why Would You Use an Opendime?
Because each Opendime is so cheap, you can use them just like cash. Load them up with Bitcoin (BTC) and trade them for anything else without requiring an on-chain transaction.
Some other use cases:
- Secure short-term storage of small amounts of Bitcoin (BTC).
- Hand it over when exchanging Bitcoin (BTC) for cash (or better, gold).
- Gift them to others!
How Does an Opendime Work?
Think of the Opendime like a portable cryptocurrency piggy-bank.
You can throw in as much Bitcoin (BTC) as you like, but you cannot spend any of the Bitcoin (BTC) stored on an Opendime until you destroy it. Once you’ve popped out a small chip on the Opendime, it’ll reveal this private key and the funds can be retrieved.
The Opendime does not reveal the private key to anyone before this chip is popped out. Once the private key on an Opendime is accessible, it’ll also flash differently when it’s plugged into a device to let you know.
Coinkite’s Opendime is sold in packs of free for about $40 (approx. £33). This brings the cost of each Opendime to about $13 (approx. £11).
Coinkite deliberately designed the Opendime so that it could be manufactured and sold at the lowest possible price point. That’s why the Opendime is just a barebones USB drive. The benefit of this is that each Opendime is cheap enough that you don’t feel bad when you need to destroy it to access your Bitcoin (BTC).
If you’re in the United States or Canada, then the best place to buy Opendime is from Coinkite’s official website.
If you’re from the UK or Europe, then you will likely be charged high postage fees and get stung by custom charges. Unfortunately, I couldn’t find it available on Amazon or from any hardware wallet reseller in the UK.
Setting up an Opendime shouldn’t take you longer than about 10 minutes (but probably just minutes).
- Plug your Opendime into a computer or laptop. The green light on the USB should stay on, while the red light should flash briefly. If this is NOT the case, return all the units.
- Open the USB on your desktop. There should be four files (see below).
- Open up the “index”. You should see this page.
- Find a picture (or other files) and copy them to the USB. Anything you move onto the USB isn’t saved. During the transfer, the USB will eject itself and your computer might show an error. Don’t worry about that.
- When it reconnects itself, the green light on the USB should be on, but briefly flicker.
- You should see these files now (they’ll all be read-only).
- Open the “index” file again. This will now show your Bitcoin (BTC) payment address. This is the payment address you’ll send Bitcoin (BTC) over to. You can check the balance of this Bitcoin (BTC) address and verify the device on this page.
- For peace of mind, select ‘Verify’. If the device does NOT show this confirmation, then contact Opendime support.
- Send Bitcoin (BTC) to the payment address. Verify the balance by selecting ‘Check Balance’ in the “index” file, or copy the payment address into any third-party Bitcoin (BTC) blockchain explorer (e.g. Blockchain.info).
Until you want to spend these funds, that’s all you need to do. It’s critical that you make sure you keep the device safe though, as you cannot access the Bitcoin (BTC) stored on it without the device itself. You cannot take a backup of an Opendime in case you lose it.
Unsealing the Opendime
When you’re ready to access the funds, you’ll need to ‘unseal’ the Opendime. This permanently changes the device in order to reveal the private key.
Once you’ve done this and swept the funds (i.e. moved all funds in the Opendime into a secure wallet), the device should be disposed of.
Before unsealing your Opendime, make sure that you:
- Have access to a secure machine. I used a laptop which had just been reinstalled.
- Understand how to sweep funds using your preferred wallet. I used Electrum (on macOS) for this guide. Search for keyword “sweep” in your wallet documentation if you’re not sure how to do it.
I swept the funds to a desktop wallet, but you can sweep to a mobile wallet too. If you are sweeping to a mobile wallet, disable the Internet connection on your desktop before connecting the Opendime to it.
- To reveal the private key, you need to poke out a chip on the Opendime. Something like a pin or paper clip will work fine. This video shows you how it’s done.
- Once you’ve moved this little chip, the private key is no longer hidden.
- Plug the Opendime into your computer. It should now alternate between flashing green and red. This confirms that the private key has now been revealed.
- Open up your Electrum wallet. Go to Wallet > Private Keys > Sweep.
- In the window that pops up, select the small folder icon in the bottom right. Select the file named ‘Private Key’ on your Opendime. You can leave the other settings alone in Electrum.
- Something like this should pop up. This just confirms that you’re sending the funds from the Opendime to your own wallet.
- Once the transaction has confirmed, the Opendime is now trash. You’re safe to bin it.
Summary: The Bitcoin Bearer Bond
I think Coinkite’s Opendime is awesome. There’s nothing else like it that’s available on the market.
The Opendime is playing a completely different game. It’s straight out of a cyberpunk novel (‘credit sticks’) and allows you to use bitcoin without having to make an on-chain transaction (i.e. just like cash).
However, because the unit doesn’t show the private key to anyone (which is great and part of the design), there’s no way to back it up. This means that the Opendime is only really suitable for storing smaller amounts (i.e. any loss you could shrug off) of Bitcoin (BTC). Just like cash, there’s nothing you can do if your device is lost, stolen, or broken.
I’d be hesitant to recommend this to a complete beginner intending to store all of their funds on. It’s better than leaving your Bitcoin (BTC) stored on an exchange, but there are much better alternatives if you’re looking to put your Bitcoin (BTC) into long-term storage (which is covered in my hardware post roundup).
In my opinion, these devices are best suited for those who already have familiarity with cryptocurrencies and want another little device to add to their toolbelt.
Anything to add?
Thanks for checking out this Opendime review!
Have a question about the Opendime? Or want to share your thoughts about it?
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