I've noticed that the attachments of "secure" notes are stored unencrypted on the file system. I think that's a misleading definition of "secure" note.
The use case: I'd like to store confidential images. Previously I set up a script which would decrypt the encrypted image, open the unencrypted image with the default application (just call open in the shell) and delete it once the preview application has loaded the file. This way the file contents would be loaded into memory and removed from the file system as soon as possible. Can you set up a similar on-the-fly encryption/decryption for attachments or support images directly?