Why Cold Storage Matters
Hot wallets (connected to the internet) are convenient but carry inherent exposure risk. Cold wallets keep your private keys offline, dramatically reducing attack surface. The Stronghold x Tangem card takes this further by eliminating a traditional seed phrase entirely.
How the Co Branded Tangem Card Works
Your Stronghold x Tangem card generates and stores your private key directly on the card's secure chip. The key never leaves the card and is never transmitted, viewed, or stored anywhere else, not on Tangem's servers, not in the app, nowhere.
Key technical facts:
- Uses a Common Criteria EAL6+ certified secure chip, one of the highest consumer security certifications available
- Communicates via NFC (tap-to-sign), no Bluetooth, no wires, no battery required
- Seedless by default, though an optional BIP39 seed phrase can be enabled for those who want traditional cross-wallet compatibility
Best Practices
1. Understand Your Backup System
Cards come in sets of 3. Each card is a full, independent copy of your private key, not a fragment. Losing one card doesn't compromise security since the private key is protected by the chip while the user has backup cards..
2. Store Backup Cards Separately
Never keep all cards from a set in the same physical location. If they're stored together and that location is compromised (theft, fire, flood), you lose all redundancy at once. Moreover, 2 cards allow password reset. Treat each card like a separate physical key, distributed geographically.
3. Set an Access Code
Adding a password/access code creates a second layer of protection. Make sure it is strong and, ideally, truly random. With it, a lost or stolen card is far less useful to whoever finds it.
4. Know the Recovery Limits
If every card in your set is lost or destroyed and no seed phrase backup was configured, access to the funds is permanently gone. There is no support ticket, password reset, or recovery service that can restore it. This is the tradeoff of true self-custody: no third party can help you, but no third party can access your funds either.
5. 3-Card Set for Larger Holdings
A 3-card set provides an additional layer of redundancy over a 2-card set and can also serve as a simple inheritance mechanism: one card can be shared with a trusted family member as part of a succession plan.
The Bottom Line
Self-custody means the responsibility for security sits with you, not a bank, not an exchange, not Stronghold. The tradeoff is real independence: no one can freeze, seize, or lose your funds on your behalf. Following these practices ensures that independence doesn't come at the cost of avoidable risk.
A Note on Recent Industry News
Self-custody has been under a spotlight this week following a hardware wallet vulnerability disclosed by another provider, tied to how that device generated private keys during setup, not a flaw in any blockchain itself. It's a reminder that "offline" alone isn't a guarantee, the underlying key generation process matters just as much.
That's why the Tangem architecture uses a certified hardware random number generator with entropy drawn from the chip's own physical sensors, independently audited by two separate security firms to confirm there are no backdoors or weaknesses in that process. If you have any questions about the security architecture before purchasing, our team and Tangem's are both here to help.
