The passphrase, or 25th word
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 5 min
In short
A passphrase is an arbitrary string you can add to a seed phrase, and adding it produces a completely separate wallet. It means a stolen phrase alone does not reach your funds — but forget it and no one, anywhere, can recover the wallet.
Key points
- Added to a seed phrase, it yields a different wallet
- Part of the BIP39 standard, not a vendor feature
- Forget it and there is no recovery and no support desk
- A one-character difference opens a different wallet
Definition
An arbitrary string mixed in when BIP39 derives the seed. It need not come from the word list and has no length or character restrictions.
It is nicknamed the 25th word, but it need not be a word at all. Any string is folded into the seed derivation and yields a different 64-byte seed. Since it is outside the word list, no checksum protects it: get one character wrong and you do not see an error, you see a different — usually empty — wallet.
The benefit is that finding your written phrase is not enough. Restoring without the passphrase shows an entirely different set of addresses. Some people keep a small balance there as a decoy, though whether that helps under coercion depends on assumptions you should not lean on too heavily.
The hard part is storing the string. Write it beside the phrase and you have gained nothing; keep it only in your head and a lapse or an accident freezes everything. The workable compromise is a different location and a different form from the phrase, plus, if inheritance matters, a way for your family to learn about both.
Watch out for
- · Forget the passphrase and the correct seed phrase will not bring the funds back
- · Writing it on the same paper or in the same safe adds no protection at all
- · If your family does not even know one exists, the assets are lost on inheritance