21 BTCSeed phrase
In plain words
A seed phrase is a list of 12 or 24 ordinary words that can recreate all the keys of a wallet. Whoever has the words has the bitcoin, so write them on paper or metal and never type them into a website.
Short definition
12 or 24 words (BIP39) that back up all keys of a wallet.
How it works
The words encode a random number plus a checksum (BIP 39). The wallet turns them into a master key and derives every address from it (BIP 32 and later standards), so one backup covers all past and future addresses of that wallet.
An optional Passphrase (a “25th word”) creates a completely different wallet from the same words.
Keeping it safe
- Write it down by hand; no photos, cloud notes or password managers synced online.
- Steel plates survive fire and flood.
- Nobody legitimate will ever ask for it: “support” asking for your words is a scam.
- For larger amounts consider Multisig, so one lost or stolen backup is not fatal.
See also
- PassphraseOptional extra word(s) added to the seed that create a separate hidden wallet.
- Hardware walletA hardware wallet is a small device that keeps your private keys offline and signs transactions inside itself. Even if your computer is infected, the keys never leave the device.
- Private keyThe secret number that authorises spending. Whoever has it controls the coins.
- MultisigMultisig means a payment needs several keys out of a set, for example any 2 of 3. Losing one key, or having one stolen, does not lose the coins.
- Hot / cold walletHot: keys on an internet-connected device. Cold: keys kept offline.
References
- BIP 39 (github.com/bitcoin/bips) github.com
- BIP 32 (github.com/bitcoin/bips) github.com