I’d like to sign messages with trezorctl and enter the message on the computer. however, I don’t want the Trezor to pass the signature back to the computer (as it happens by default with trezorctl sign-message), rather it should stay on the Trezor and be displayed only on its screen (Model T), preferably in the encoding of my choice (e.g. binary, hex, base64).
the use case is what we’ve been discussing in the other thread (forum.trezor. io/t/generating-mnemonics-with-a-trezor/11578/2), using deterministic randomness as a source for generating child mnemonics. I had signatures in mind, and the problem is that going either route causes the (now-)secret to leave the Trezor. displaying it only on the screen would allow constructing a mnemonic with the help of a word list.
of course, implementing BIP85 (github. com/trezor/trezor-firmware/issues/1528) would make this unnecessary.