Great question. At some point, in order to use Bitcoin, you’re going to need a computer.
Hardware wallets compute all the time. For example, they compute addresses from XPUBs. They compute XPUBs from seeds and so on.
A BIP-39 checksum word contains bits from the SHA256 of the actual entropy payload. Calculating this SHA256 sum by hand is intractable.
So, in my opinion, the hardware wallet SHOULD be wiling to generate a checksum word for you based on the incoming entropy. ColdCard will do this. I believe SeedSigner will as well. Last I checked, Sparrow WILL NOT do this for you. There are various other tools that may have this capability.
But yeah, at the end of the day, you need multiple independent vendors to perform these kinds of calculations:
- Generating the last word of a BIP39 seed phrase
- Generating an XPUB from a seed phrase
- Generating a master key fingerprint (XFP) from a seed phrase
- Generating addresses from an XPUB
Hardware wallets are powerful enough to do these things. Whether and how many is up to the vendor to implement.
