[julie78787]

Except that you can attack stored encryption secrets either off-line, or with the same privileges as the user.

If they are hard-coded in the binary, they can be extracted off-line by another use with the same binary. If they are generated at run-time, they have to be stored with permissions that grants the user access to their own resource.

There are programming techniques for sharing a file descriptor, but they aren't portable. That makes generating a keypair, then sharing an open file descriptor to the file containing the keypair impossible.