Understand custody · Backups

Twelve Words Are Not a Password

A list of 12 or 24 words looks like a sentence but behaves differently. It is an encoded random number with a checksum.

From randomness to words

BIP 39 begins with 128–256 bits of entropy, appends a checksum, and splits the result into 11-bit groups. Each group selects one word from a 2,048-word list.

This produces sets of 12, 15, 18, 21, or 24 words. The checksum catches some transcription errors but does not replace a tested backup.

One backup, many keys

The mnemonic becomes a seed, and a deterministic wallet derives many keys and addresses from it.

A photograph, cloud note, or message containing the words therefore becomes a single point of compromise.

The optional passphrase

BIP 39 permits an additional passphrase. Every value creates a different valid seed; a typo opens another, usually empty wallet rather than showing an error.

Losing that passphrase can make the correct 12 or 24 words insufficient.

A seed phrase is access in readable form, not a hint toward access.

Sources and verification

  1. BIP 39
  2. BIP 32

Never share a real seed phrase. This archive does not request one for verification, participation, or recovery.

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