Learn more about Coldkey

Verify Coldkey authenticity

You can verify that every Coldkey is authentic.
For this, we use AuthKeys.
They are unique random strings directly printed on the card. We only keep a copy of the fingerprint of an AuthKey so it exists only on the card.
By using our authentification tool you can verify if the wallet you hold is authentic or a counterfeit.
For more security, there is one plain AuthKey, and a UV AuthKey that requires a UV black light to be revealed.

Secure card wallets

Coldkeys are made in a way that makes it impossible to reveal the secret data needed to spend your funds unless you physically damage the card.
You need a pair of scissors or a sharp blade to cut through the protective layer on top of the hologram, then only you can peel it and redeem the funds on that private key !


Bech32 addresses

Coldkeys use bech32 addresses. These are the most up-to-date form of addresses available on the bitcoin network.
The benefit of addresses starting with "bc1q" compared to those starting with "1" is that you save ~40% on the Bitcoin transaction fee.

Crypto Key

Private Key

This is the most basic piece of cryptographic data used with blockchain assets.
Only the right private keys allow you to spend funds that you have received.

Compatible with most wallets

Coldkeys use private keys. They are not a "refund code".
You can spend a Coldkey with any computer that has a webcam, or an Android smartphone. So, no one else than you can decide to reveal the private key and spend the funds.

Recognized by the bitcoin community

While designing Coldkeys, we kept in touch with members of the Bitcoin community. Our wallet cards have been warmly welcomed, and it appears that Coldkeys satisfy most of the requirements for their intended use, as cold storage. Please check our announcement :

How to spend Coldkey

"I find the prospect of mass-adopted physical wallets very exciting for a number of reasons[...]"

Sat0shisGhost on Bitcointalk, while reviewing Coldkey

You need to carefully cut the card with a pair of scissors, or around the hologram with a knife. Then you can peel the hologram and reveal the private key.

If you have an Android smartphone, we recommend using Mycelium. Otherwise with a computer that has a webcam (Windows or Mac) you can use Electrum to import the private key as QR code.

Feel free to contact us if you need any further help !

Here is a link to the same picture but with a better resolution, so you can try the private key with Mycelium on Android and see how easy it is to spend Coldkeys ! Please follow this link : (Our first prototypes used legacy bitcoin addresses starting with "1")



Verify your Coldkey authenticity


We take counterfeiting very seriously.
Despite all the efforts that can be done by using only top-notch security materials, we have implemented AuthKeys
By visiting our authentication tool : you can easily verify if the Coldkey you hold is genuine and was made by us.

There are two different AuthKeys on each Coldkey card : one in plain text, and another one in UV. The latter one requires a blacklight in order to be revealed.
We keep no copy of the Authkeys, only hashes (their fingerprint) so we can always compare the data on the card to our records.

I can safely say these are very cool in hand. I am testing their various properties from build to security qualities. So far, the verdict is good. They're VERY well made.

Vizique, on Bitcointalk