Quickstart! Start Here!
About the Bag
Your coldcard should have arrived sealed in a special bag: It has a large Coinkite logo, green text and a barcode with number underneath. This number is important and we call it the "bag number". Please make note of this number because the Coinkite factory has recorded this number into the secure area of flash memory of your Coldcard.
Before opening it yourself, please inspect the bag for damage or signs of being previously opened. After you open the red seal, it will show the word "VOID". If you find anything out of place, please contact firstname.lastname@example.org with photos.
The purpose of the bag, and it's unique number, is to give you confidence that the Coldcard has come directly from the factory and has not been modified by anyone before you get started.
This is merely one of many layers of our security, and we know that plastic bags can be "hacked" with sharp knives and so on. This is an example of "Defense in Depth".
Connect a power supply to the Coldcard using the USB port at the top. Any Micro USB cable you already have can be used. You can connect the USB to a computer, but at this stage, a wall charger or USB power pack could also be used. We just need power, not data.
Terms of Sale
The first screen you will see looks like this:
If you look closely at the right edge, there is a small scroll bar and arrow pointing downwards. Use the 5 and 8 keys to move up and down and see the full message.
The complete terms document can be found here. Press the OK key (checkmark, lower right) to accept the terms and continue.
Before a Bitcoin seed is generated, you must select a primary PIN. This is your main defence against random people using your Coldcard when you are not around. Please pick good PIN codes!
On the Coldcard, the PIN consists of two parts, like these examples:
12-34 1234-5678 872323-39843 12-345678
The first part is called the prefix (1234-) and the second, the suffix (-4567). Each part must have between 2 and 6 digits. The prefix determines the anti-phishing words you will see each time you login.
When you pick your PIN code, you'll see the anti-phishing words associated with the PIN prefix. These words will be unique for each Coldcard. You may want to experiment with a few different PIN prefixes until you find some fun or memorable words. Regardless, you will need to remember those words, as it's important to verify those words before proceeding to the second part of the PIN—every time you login to the Coldcard.
As usual, you be asked to confirm the new PIN and enter it a second time.
New Wallet or Import
Once your PIN has been established, it's time to setup your wallet. You should see a menu like this:
If you already have a BIP39 seed, or a backup from another Coldcard, or even a XPRV (extended private key), you should choose Import Existing menu item. However, most new users will start with New Wallet.
New Seed (New Wallet)
Choose New Wallet to generate 24 words using the BIP39 word list.
The words are shown to you, and if you don't like them, you can press X to start over. Write down the seed words, in order, on the provided card or some other paper. Please be careful at this stage and be 100% sure that each word is recorded correctly. You might want to duplicate them by hand at this point too (ie. make backup copy).
Once you've written them all down, press OK to continue to the quiz. The Coldcard will ask you what each word is, in random order. We do this to verify your backup is correct. If at any point, you are unsure of a word, you may see them again by pressing OK.
If you press X to cancel, these words will be forgotten and the entire process would need need to start over!
If you complete the quiz successfully, your new Coldcard is ready to be used.
From this menu, you can import seed words generated on another system. Choose the number of words: 24, 18 or 12 words and the following menus will allow you to drill down to appropriate BIP39 word (English only).
Alternatively, you can import a backup file from another Coldcard. You will need the backup file (7z) on the MicroSD card, and you must enter a 12-word password that was provided at the time the backup was created.
To import an XPRV, you must provide a cleartext file on MicroSD
with a BIP32 base58-serialized extended master private key. It
should start with
xprv and be on a single line of a text file.
We don't care what else is in the file. Please note there is no
encryption for this method, and therefore, it is somewhat hazardous
and only recommended for testing purposes.
Ready to Sign!
Once your PIN code and master seed have been established, your Coldcard is ready for daily operation. You should see a menu like this one:
If the USB port is connected to a computer, the Coldcard makes itself available to that computer. (The Coldcard is invisible to the attached computer, if any, until the PIN code is correctly entered.) You can use a desktop wallet, such as Electrum, to pair with the Coldcard and then send it transactions to be signed.
Alternatively, you can use a MicroSD card to bring in transactions and sign them.
Using with Electrum via USB
- install Electrum version 3.2.3 or later, with Coldcard support: download here
- select "New/Restore" from File menu
- pick file name
- pick "Standard Wallet"
- pick "Use a hardware device"
- select the Coldcard device shown
- choose Segwit or classic address format
- operates like any other USB hardware wallet
Using Coldcard Offline
- secure quality MicroSD cards of small size
- on the Coldcard, go to: Advanced > MicroSD Card > Electrum Wallet
- read and approve the warning message, like this:
- a new file,
new-wallet.json, is written to the MicroSD
- remove card, take to a computer running Electrum
- your Electrum client must have the Coldcard plugin enabled
- open the wallet file, and wait for sync to complete.
- you may want to keep the wallet file (which now has many additional details about change addresses and so on) elsewhere on your computer.
- your new wallet will use old-style (not segwit) payment addresses for maximum compatibility
When you want to spend from this wallet:
- open the wallet in Electrum
- setup your new transaction as usual
- choose Preview transaction, then the "Save PSBT" button
- you can save directly to your MicroSD card.
- use a short file name that describes transaction or has the date; must end in
- move that card to the Coldcard
- select "Ready to Sign" from main menu of the Coldcard
- pick today's PSBT file from the list (if there is more than one on the card)
- approve the details of the transaction
- the resulting transaction will be saved back to the card, under the same filename with new
- use any copy of Electrum, or a public service to push the hex-encoded transaction from that file
- for example, in Electrum, use Tools > Load transaction > From file
Keep your Coldcard in a safe location. Everytime you remove it from storage and use it, please consider the following:
- Are there scratches on the case?
- Is the light green or red? It should be green!
- Are the anti-phishing words correct? Do not enter the rest of your PIN if you are unsure.