SeedSigner doesn't support message signing for multisig keys — it throws "Not implemented" for any m/48' derivation path. I raised this as an issue two years ago, no fix came, so I patched it myself.

The change is small (21 lines) and the actual signing function already worked — it was just the path parser blocking multisig paths unnecessarily.

I use message signing for key ownership and control verification in multisig SMSF custody setups via Gatekeeper (https://gatekeeper.dpinkerton.com). Coldcard handles this fine, but SeedSigner users were stuck.

Blog post: https://blog.dpinkerton.com/posts/patching-seedsigner-multisig-message-signing/
PR: https://github.com/SeedSigner/seedsigner/pull/874
Patched image (Pi Zero): https://github.com/AusDavo/seedsigner/releases/tag/0.8.6-multisig-msg-signing

#seedsigner #bitcoin #multisig #opensource