Seed phrase
A seed phrase is a set of 12 or 24 words from which every key in a wallet is regenerated. It is the access itself: whoever knows the phrase owns the funds, and if you lose it there is no way to recover it.
How it works
The words come from a fixed 2,048-word list defined by BIP-39. Every private key and address in the wallet is derived mathematically from that sequence, and always derives to the same result.
That is why the phrase can be typed into any compatible wallet on any device and produce the same addresses holding the same money. The app stores nothing; it recomputes the keys from the phrase each time.
For the same reason the phrase cannot be reset or changed like a password. No support desk exists that can restore it, and anyone offering to is lying to you.
Why it gets stolen rather than cracked
Here is the size of the space a 12-word phrase covers.
| Words in the BIP-39 list | 2,048 |
| Phrase length | 12 |
| Entropy | 128 bits |
No amount of computing power brute-forces that. So phrases are not cracked, they are taken from the owner: off a screenshot in the gallery, out of a cloud note, through a fake "wallet recovery" page or an impostor support account.
How to store it
- Offline onlyPaper in two separate places, or stamped into a metal plate. Photos, screenshots, notes apps and messengers are out.
- Test the restore before you need itA phrase written down wrong reveals itself at the worst moment. Restore the wallet on a clean device and confirm the addresses match.
- Nobody legitimately asksNot wallet support, not an exchange, not a "compatibility check". A request for the phrase is the attack itself, without exception.
- Plan for inheritanceIf nobody but you can find the phrase, the money leaves with you. A sealed envelope with a notary, or splitting the phrase into parts, solves it.
- The extra wordBIP-39 lets you add your own passphrase on top. It protects against the paper being stolen, and losing it loses the money just as finally.