Following up on my previous guide about seed phrase generation, I just published a new guide on seed phrase splitting.
If you're looking to harden your Bitcoin single-sig backup and protect yourself from the infamous $5 wrench attack, check it out.
I covered 3 methods, but only one of them is really reliable.
Feedback welcome.
why not use XOR? Then each shard is its own valid mnemonic and can be used as an independent wallet (or plausible deniability).
I'm not familiar with XOR splitting. Would you have a guide for me to look into?
From my quick search, it looks like you need all the shards to recover the original seed, which isn't great for loss protection. You'd have to back up each shard separately, which complicates storage.
Anyway, I focused purely on manual methods that can be done with just pen and paper. If XOR needs hardware wallets or digital tools, I'd treat it like Shamir Secret Sharing: interesting but outside the scope of this guide.
ah yeah you could I think do XOR by hand but I sure wouldn't want to.
I would think the easiest way to be purely manual is to just use a passphrase. it's easily memorizable, and it doesn't look like a seed phrase so you can hide it in multiple places, even pretty openly, as it doesn't on its own reveal or even imply anything.
You could also consider a "border wallet", which requires some digital prep like printing a paper, but I don't think it requires you to use a computer for calculations.