Coldcard
Coldcard is an air-gapped hardware wallet for Bitcoin, made by Coinkite, that stores private keys offline and signs transactions without internet exposure.
What Is a Coldcard?
A Coldcard is an air-gapped hardware wallet for Bitcoin. Coinkite manufactures it. The device stores private keys offline. It signs transactions without internet exposure.
Coldcard users generate seeds using built-in dice rolls or import them securely. To spend Bitcoin, users create a transaction on an online computer. They transfer it to Coldcard via microSD card or QR code. Coldcard verifies and signs the transaction offline. Users then export the signed transaction back the same way for broadcasting.
Coldcard matters for security. It isolates private keys from malware, phishing, and network attacks. Bitcoin-only focus reduces software vulnerabilities. Features like duress PINs (reveal decoy wallet under coercion) and anti-phishing words protect users further.
Key characteristics include:
- Air-gapped design: No wireless connectivity; USB for power only in signing mode.
- Secure element: Uses a dedicated chip for key storage.
- Open-source firmware: Users verify code integrity.
- Models: Mk4 (standard), Q1 (QR-focused), WalletGuard (NFC reader).
- Seed support: BIP39, SLIP39 shamir shares.
Examples: Long-term holders use Coldcard for 'HODLing' sats securely. Power users combine it with multisig setups.
Bitcoin (BTC) is the first decentralized cryptocurrency, launched in 2009. It uses blockchain technology for secure, peer-to-peer digital transactions without intermediaries.
Read full definitionPlausible Deniability refers to the ability to deny knowledge or possession of cryptocurrency by using techniques like decoy wallets or hidden volumes, ensuring privacy under duress.
Read full definitionBIP39 is a standard for generating mnemonic seed phrases that are used to create deterministic wallets and securely back up cryptocurrency private keys.
Read full definitionShamir Secret Sharing (SSS) divides a secret, like a crypto wallet seed, into multiple shares. A threshold number of shares reconstructs it, enhancing security as in SLIP-39 backups.
Read full definitionMultisig (multi-signature) is a security feature that requires multiple private keys to authorize a transaction, enhancing protection against unauthorized access in blockchain networks.
Read full definitionReal-World Examples
Example 1: HODLing Bitcoin securely
Alice buys Bitcoin for long-term storage. She uses Coldcard's dice roll feature to generate a BIP39 seed offline. She writes down the 24-word mnemonic and stores Coldcard in a safe deposit box. Her private keys stay air-gapped.
Example 2: Signing a transaction
Bob runs a watch-only wallet on his online laptop. He creates a transaction to send 0.1 BTC. He saves it to a microSD card. He inserts the card into his Coldcard Mk4, verifies details on the screen, enters his PIN, and signs it. He returns the signed transaction to his laptop via SD for broadcasting.
Example 3: Multisig setup
Carol sets up a 2-of-3 multisig vault. She uses Coldcard as one key, a software wallet on another device as the second, and a Trezor as the third. To spend, she signs her Coldcard share offline and combines signatures.
Example 4: Duress protection
Under coercion, David enters his duress PIN on Coldcard. The device displays a decoy wallet with minimal funds. His real Bitcoin remains hidden in the main wallet, protected by the primary PIN.
Bitcoin (BTC) is the first decentralized cryptocurrency, launched in 2009. It uses blockchain technology for secure, peer-to-peer digital transactions without intermediaries.
Read full definitionBIP39 is a standard for generating mnemonic seed phrases that are used to create deterministic wallets and securely back up cryptocurrency private keys.
Read full definitionA watch-only wallet displays cryptocurrency balances and transactions without private keys, allowing secure monitoring without spending capability.
Read full definitionMultisig (multi-signature) is a security feature that requires multiple private keys to authorize a transaction, enhancing protection against unauthorized access in blockchain networks.
Read full definitionA Hot Wallet is a cryptocurrency wallet connected to the internet, allowing for easy access and transactions but more vulnerable to hacks.
Read full definitionTrezor is a hardware wallet by SatoshiLabs. It stores private keys offline to secure cryptocurrencies.
Read full definitionA Duress PIN is a special code used in cryptocurrency hardware wallets to trigger a response, such as wiping the device, in case of coercion or threat.
Read full definitionPlausible Deniability refers to the ability to deny knowledge or possession of cryptocurrency by using techniques like decoy wallets or hidden volumes, ensuring privacy under duress.
Read full definitionReady to Choose a Secure Wallet?
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