Passphrase or no passphrase?

Security
1

Consider this instead of using a passphrase : only record 19 of the private key words on you “secret paper” you keep only one word in your head … you can make it in any position so when you write it down… only you know the word and the "location"in the list of where that word should be?

Thoughts?

2

You’re basically describing how the passphrase feature already works in Trezor, just with a different style. The passphrase is like a 21st word (or an extra element) that never gets written down and only exists in your head. It adds an extra layer of security to your standard 12, 20, or 24-word wallet backup.

What you’re suggesting—intentionally leaving out a word from the seed and remembering its position—is an interesting take, but it introduces some serious risks:

  1. Seed phrase structure is strict: BIP-39 and SLIP-39 wallet backups rely on a specific checksum and word order. If you intentionally leave one out, the device can’t validate or restore it unless all words are 100% accurate. One missing word could make the whole phrase invalid unless you’re brute-forcing the missing one (which gets tricky fast).
  2. Human memory is fragile: Remembering a word and its exact position for years without writing it down can lead to loss of access.

With the passphrase method built into Trezor, you can still keep 100% of your wallet backup safe and sound on paper, while the actual “secret” stays in your mind as a password you enter at unlock. And bonus: it can be anything, not just a seed word—it can include symbols, uppercase/lowercase, etc.

3

Furthermore, removing one word from the seed phrase leaves an attacker only around ~20 000 options, which a modern computer will solve in the blink of an eye.

You would need to leave out 6 or 7 words … at which point you are much better off using the multi-share feature and creating two 20-word shares, backed up and stored separately.

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