https://gitlab.synchro.net/main/sbbs/-/issues/540#note_3422
Not all public/private key pairs are protected by a passphrase (they're optional, used as an extra layer of security). Now I think what you're asking for is SSH key authentication, not SSH passphrase authentication.
--- SBBSecho 3.20-Linux
* Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)