Nostr

There's a concept of hot and cold in security. Hot things are well connected and exposed. Cold things are isolated and hidden.

When you have a Bitcoin wallet on your phone, it's considered hot because an attacker has many avenues to get the private key off your device: it's connected to the Internet, you're carrying it around and using it in public, you may leave it lying around when others are around, etc.

When you have a hardware Bitcoin signer, that is considered cold because an attacker has very limited ways of getting the private key off of it. A hardware signer, like the coldcard, creates the key on the device itself and can be used without ever connecting to the internet. The signer can also be kept in your home or in a safe when not in use, so you can make it very difficult to steal it.

These are both instances of "self-custody" but there is a spectrum of choices you can make to secure your key or keys.

Diesel 2y ago

I love my cold card and did create my seed myself, it’s very powerful to do so. Under your definition though, you can’t have a mobile wallet on your phone with the keys written down somewhere and call it cold storage? Want to make sure I’m following

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Discussion

[ARCHIVED] Jay 2y ago

I'm glad you're enjoying your coldcard. I have one too.

And yes, that phone wallet is hot as long as the private key, that value which is used to sign your transaction and make it valid to miners, is on the phone somewhere. If you lost the paper, still remembered the PIN to the app you use, and could still make a Bitcoin payment, then that's a hot wallet.

If you made a key on your phone, wrote it down, and then securely deleted the key off of your phone by, say, using Samourai wallet or throwing it into a volcano, then you'd have a cold paper wallet, which is pretty secure, but a little flimsy. Your private key only exists on that paper and nowhere else.