OpenDimes are a Bitcoin wallet in a USB stick. They are designed to be used once and physically transfer bitcoin. This article describes some of the OpenDimes coolest features, how they work, and examples of using one.
The first #Bitcoin bearer instrument, designed to securely & discreetly circulate sats in a handy USB stick.
The @OPENDIME is small, easy to conceal, and easy to transport. They measure 1/2" x 1-7/8" & can easily be kept on a key chain, a necklace, or somewhere more safe.
@OPENDIME comes in packs of three, which is convenient for keeping sats spread out between different devices. They come with a cool sticker and simple instructions.
Once you plug in your @OPENDIME it will light up with a stationary green light and a flashing red light. They plug into any laptop, computer, or phone USB socket. They act like a read-only USB flash drive.
Simply drag & drop a random file of yours into the root of the @OPENDIME. You need at least 256k bytes which the device will use as entropy to create your private key. You have a little more than 1 MB of room, so files that are too large won't work. README.txt has resources.
The @OPENDIME may eject itself & then reconnect after it has written the private key. Now you have a QR Code.jpg file & address.txt file that you can send sats to. The red light should no longer flash.
Now you can use your favorite mobile wallet to scan the QR code & load some sats on your @OPENDIME. Or you can copy/paste the address which is saved to a .txt file. In this example, I used my Greenwallet to deposit 50,000 sats.
Let's review what we've done so far: Loaded random bytes, generated private key & corresponding address, then deposited some BTC. The private key never leaves the @OPENDIME, we have essentially secured 50k sats on a small device that can be easily & discreetly transferred.
That's pretty powerful when you think about it. Swap @OPENDIME with your friends to "coinjoin", pay someone like you would with cash, transport life-changing amounts of BTC undetected across borders. The world is your oyster.
You can use a block explorer to easily check the address of your @OPENDIME. Be aware of the privacy considerations when using these tools though. Or plug into any device with a wallet capable of sweeping keys to transfer to that wallet. In the mean time, stash your sats.
Now that I have a USB-C OTG adaptor, I can demonstrate how to sweep an @OPENDIME into @SamouraiWallet.
@BitcoinQ_A did a thorough & detailed explanation of this process here: https://twitter.com/BitcoinQ_A/status/1271123885711384579
To check the balance & verify the private key is still intact, plug the adaptor & @OPENDIME
into the Android. A prompt will ask if you want @SamouraiWallet to handle these devices by default. Then the balance, address text, QR code, & a link to view on OXT are shown.
Now for the fun part! In order for the private key to be exposed so @SamouraiWallet can read it, a small chip needs to be removed from the @OPENDIME. Poke a hole through the device & pry the chip off the board, this is called unsealing.
When the @OPENDIME is plugged back into the Android, @SamouraiWallet will give you the option to sweep the private key. This works because the OpenDimes are implementing the Wallet Import Format (WIF) Bitcoin wallet format. This is a decent explainer article on WIF:
Basically, there is one address and one private key. You can send bitcoin to the address as much as you want and the funds are safe so long as you have possession of your OpenDime. The only way the private key will be exposed is by removing that little microchip as explained above. Once that chip is removed, it alters the code on the OpenDime and writes the Private key file allowing it to be read by wallets with sweep capabilities like Samourai Wallet. Once the funds are swept to another wallet you may as well turn the OpenDime into a keychain or throw it away or something. It will still function, you can still send funds to that same address, you can still sweep them, but the private key has been exposed and anyone could plug your OpenDime into a computer and grab that private key instantly and sweep your funds. So once you use your OpenDime, don't re-use it, it's not safe.
You'll notice that the lights on the @OPENDIME flash in a syncopated fashion, giving the user a clear visual indication that the private key has been unsealed.
@SamouraiWallet asks for a confirmation then the tx is broadcast across the Bitcoin network. Overall that was easy & intuitive! Check the tx on OXT. Join a whirlpool. Use a Dojo ;)
Thanks for reading! I hope you enjoyed this article and see some utility in using an OpenDime for some of your Bitcoin needs. Opendimes are a great way to privately transact in Bitcoin like cash, the funds are secure, nobody knows the private key until the microchip is removed, and exchanging an OpenDime with someone doesn't leave any transaction on the blockchain.
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This article is available on Twitter as a thread here.