Hi, I’d like to revive an old SLIP, SLIP-0012 slips.readthedocs .io/en/latest/slip-0012/ (“Public key encryption using deterministic hierarchy”). It has draft status and hasn’t even been filled out. Basically, what I’d like to do is encrypt messages on some untrusted device and be able to decrypt and view them entirely on my Trezor. This would massively improve usability for certain use cases where you don’t need interaction with the device, such as adding a new password to your Trezor-backed password manager. This would avoid the major shortcoming of SLIP-0015, which also has the goal of safely encrypting metadata but stores a derived encryption key in memory on the unsecure device and only protects cloud backups.
Considering SLIP-0012 was created over 11 years ago and never even filled out, and I got no response asking before, I don’t expect SatoshiLabs to build support for this. But I’m willing to take the initiative, and have a crack at the implementation myself. I would appreciate some guidance on whether this feature would be something Trezor would be willing to accept, under the ideal assumption that I am perfectly competent and capable. (I’d also appreciate pointers about the implementation.) I believe it would be implemented similar to SLIP-0011 (encrypt_keyvalue/decrypt_keyvalue), via ECIES with ephemeral keys on the encryptor side and possibly reusing the ECDH types used by sessions.