How does it work and why is it secure?

Hi, I'm Paul, the creator of the Tamahagane Bitcoin Card, and I want to tell you how the card is made and explain how security works.

About me: I've been a software engineer for 25 years, and I've always been interested in security, privacy, and cryptocurrency. I gave Bitcoin gifts in the past but it was not easy. There were no products that I trusted, and definitely nothing nice enough to give as a gift, so I made my own. They evolved from paper into laser-engraved metal. Then, since I happen to work at Shopify and I love using our own product, I decided to set up an online store and make them available to anyone.

How it works

Technically a Tamahagane Bitcoin Card represents a Bitcoin "wallet". A Bitcoin wallet is a digital code that contains secret cryptographic "keys" that provide access to the funds on the Bitcoin blockchain ledger, and a public address to receive funds.

All of this can be encoded into a unique phrase made up of 12 common English words, this is called a "seed phrase". It allows anyone who knows it to recreate the wallet (this is done automatically and easily by the Bitcoin wallet app), including the private keys, and then withdraw the funds, so the seed phrase must be kept secret!

The Tamahagane Bitcoin Card has the seed phrase permanently laser engraved on it. It must be kept secret, so you need to be sure that it has never been seen during production or during shipping. Read on to learn how you can know it has never been seen.

Security during production

The details stored on the Tamahagane Bitcoin Card are never in contact with a computer that’s Internet-connected. They are generated on a computer that is permanently disconnected from the Internet (it has no wi-fi and no network connection at all). This computer is connected to an offline laser engraver (by a USB cable, no network!), which engraves the details on the card, and the secret seed phrase is immediately concealed by the tamper-evident covering. The system is then reset with all data securely wiped. I personally make each and every card myself, in my locked private workshop, so the cards are never seen by anyone without the seed phrase hidden by the sticker.

Security during shipping

The “tamper-evident covering” is a special sticker. It cannot be removed and replaced without showing obvious evidence (it shows a pattern when removed, you can't miss it!). And each sticker has a unique code on it, which is emailed to the buyer, so you can also be sure that it wasn't removed and then replaced with a different one.

Security during storage

The way Bitcoin works is that the funds are technically "in the cloud", on the Bitcoin blockchain ledger. The "seed phrase" on the Tamahagane Bitcoin Card is needed to access the funds, and it can be used by anyone who knows it, even if they don't have the Tamahagane Bitcoin Card in their possession. So keep the seed phrase covered with the tamper-evident sticker until it's time to use it. Never let it be seen or photographed.

But the good news is that if you keep it physically safe with the secret seed phrase hidden, it's safe from theft by hackers and viruses since it's not stored on a computer. This is known as “cold storage”, and it’s the safest way to store Bitcoin.