The coldcard and trezor both has support for a passphrase. What amount of characters in this passphrase that would be considered unbreakable with current technology and within some years of bruteforcing?

2 Answers 2


Depends. Best to use a passphrase pulled from wordlists, like EFF Diceware's or BIP39, so then six words.

But do not go over 49 characters.

You can get away with a string under 20 characters if the characters are truly random generated, upper/lower.

Using a password manager is a great way to go if you don't want to use physical dice or coins.

Whatever you do, do NOT create one from your own brain, easily crackable in a short time no matter what, must come from high entropy, randomly generated.


Dont use a password manager, they tend to get hacked and leak information.

Dont use a random generator, if you loose it, you will never be able to guess it.

Usually 20+ character is a good and safe lenght, add names or words you could remember, adding numbers or dates.

Having helped hundreds of people with lost passwords, my experience is if you use a too complicated password, your will have a hard time restoring it if you loose the note.

If the passphrase would be just the password to your wallet, then disregard above, but since its used with a 24 word seed then its just an additional layer that does need as much security as a normal password would.

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