The practical security implications of an exposed 24 word seed phrase with "blanks"

Question

I want (a substantial amount of) the strength in numbers of a self-custody 24 word Bitcoin wallet, but I don't want to memorise all 24 words; laziness prevails.

My idea: create a note (probably digital) containing n of the 24 words, in order (not scrambled), and to only memorise the n number of blanks. The n blanks will not be in digital form and will be fully committed to memory.

E.g. 8 of the 24 words are left blank in the note:

grab merit ___ can
___ ___ floor car
exit mother ___ festival
october ___ camp ___
trial nephew ___ fabric
galaxy napkin ___ apple

Note: This seed was referenced from here.

Out of curiosity, does the location of the blanks offer a varying number of possibilities? E.g. having the blanks front loaded, rather than spread out?

I'm pretty flexible with this, in the sense of hitting the "sweet" spot with how many word omissions to remember, without considerably compromising the security of my wallet. I'd also consider a wallet/seed rotation cycle every x interval, just in case my copy with gaps is ever unknowingly compromised.

Will this strategy offer a high enough level of protection, practically speaking, or are people already cursing me with the thought of this trade off in security? Pros and cons welcomed in equal measures.

Answer 1

Will this strategy offer a high enough level of protection

"High enough" seems subjective. Someone might consider it high enough to protect 0.00003 BTC but not high enough to protect 0.3 BTC

The more complex the scheme, the more points of failure it has. If you lose your note, the words you remember are useless. If you misremember your memorized words, as humans are prone to do, especially at longer intervals, you may not be able to recover the whole phrase.

Consider what you might want to happen if you die in a car crash. Is there anybody you would like to inherit, how would they do that?

I would try to list the threats I am trying to protect against. Then I would try to list some countermeasures whose cost I think is appropriate for the sums involved.

I would try to list the possible ways I might lose control over the money through forseeable failings in memory or storage (fire, flood, mice etc) and what countermeasures might be cost effective.

Sometimes people think that knowing the seed-phrase is enough. Some of those people post questions here when they find it isn't. You might also need a note of what software you used, what version and what derivation path was selected, maybe some sample addresses that were generated etc etc. I think you need to test the recovery process.

Related:

• Help in recovering BTC from seed phrase