Phrase · 12 versus 24
12 or 24 words? Why it matters when you need to recover
Day to day, twelve and twenty-four words are equally secure: both are impossible to guess. The difference shows up at exactly the moment you are missing a word, and there the longer phrase behaves slightly better.
What they mean in practice
A twelve-word phrase represents a secret so large that trying every combination is beyond any technology we can imagine. The twenty-four-word one represents a larger secret still. Both are far beyond what any computer can traverse, so in terms of «can it be guessed?», the answer is no in both cases.
Where the difference does show
In the internal check the phrase carries. In twelve-word phrases, that check discards fifteen out of every sixteen wrong combinations. In twenty-four-word ones it is stricter and discards two hundred and fifty-five out of every two hundred and fifty-six.
Translated to your case: if you are missing one word, twelve words leave about a hundred and twenty-eight possible phrases to check, and twenty-four leave about eight. Both are trivial figures for a computer, but it explains why twenty-four-word cases resolve especially fast.
| Missing | Possible phrases with 12 | Possible phrases with 24 |
|---|---|---|
| 1 word | about 128 | about 8 |
| 2 words | hundreds of thousands | tens of thousands |
| 3 words | hundreds of millions | millions |
What to choose if you are creating a wallet now
The honest answer: it barely matters, and it certainly matters infinitely less than where you keep the paper. The number of cases lost because someone used twelve words instead of twenty-four is zero. The number lost because the phrase was kept in a phone photo, in a notes app or in an email is enormous.