When you've failed 3 times or more, we warn you that you are in danger of bricking the device. The message encourages you to double-check the PIN entered, and even gives you a peek at what you entered, before submitting it as an login attempt.

Please note the COLDCARD will brick itself after 13 failed login attempts. There is no way to reset or recover the device.

Mk2 and earlier COLDCARDs will allow infinite attempts, but make it slower and slower each time, until at one point, you have to wait hours between each attempt.

Yes, the PIN is independent of the funds being held. It can be changed at any time as long as you have the original PIN.

BIP-39 passphrases cannot be changed because the text of the passphrase is part of the private key.

You can read our secure element white paper,dual vendor secure element page, ouronline docs.and ultimately the COLDCARD source code.

• The COLDCARD can backup the seed into an encrypted file.
• New transactions to be signed can be imported from the card.
• Public key data (XPUB, payment addresses) can be written onto the card.
• Firmware upgrades can be done by copying the new firmware file onto a card.
• A skeleton Electrum wallet can be created on the card which allows Electrum to "pair" with the COLDCARD without it ever connecting to a USB port.
• Multisig wallets can be joined using files transferred via cards.

Bitcoin and Bitcoin Testnet are supported. COLDCARD does not support altcoins.

COLDCARD® generates either 12- or 24-word BIP-39 seeds. It can also import 12, 18, and 24-word, BIP-39 seeds that other wallets may have created.

There is a single "wallet", derived from the BIP-39 seed words. In addition, we have an optional "duress" wallet, which is derived from the wallet's seed words and is not independent. This means it gets backed-up automatically, and the original seed words also backup the duress wallet.

By adding a BIP-39 passphrase you can unlock nearly unlimited additional wallets which derive from the original 24 seed words. The passphrase you use defines the wallet and cannot be changed. BIP-39 passphrases are not backed up or otherwise tracked, which gives lots of freedom in terms of plausible deniability.

The ATECC608 is a fixed-function device for private key storage. It is not a general purpose CPU like some other secure elements. As a result, neither Coinkite nor the chip's manufacturer can change how it works without revising the hardware of the chip itself. It is in effect a flash ROM (read only memory) with about 10k bits of storage. All access and updates are predefined by the hardware and its design. The complete COLDCARD firmware can be seen here and we have a detailed white paper specifically about this secure element, and how we use it.

With the new mark (Mk4) of the COLDCARD, a second secure element (Maxim DS28C36B) has been added so that if either vendor has a critical security flaw, it will not affect the overall security of your seed words. We combine the power of both secure elements as described in this white paper about Mk4 secure elements

Yes, COLDCARD supports BIP-39 passphrases.

This unlocks approximately 5.9 × 10197 more wallets based on your seed words.