Janus Notes is a note-taking program for MAC OSX and iOS. They say: "To start simply add a note and begin writing. Janus supports only plain text and markdown (with preview). You can add attachments to the notes and they will live side by side with your notes. On Macintosh just press '+' (or drag and drop a file) to attach it. On iOS you can attach a picture (from the library or the camera), a link or take a voice note. Tap the attachment to see it on iOS. Double click or right click the icon on Mac to open or edit it."
Also: "Your notes will be automatically encrypted on iCloud to avoid eavesdroppers. The encryption password is available in clear in the software and can be freely changed. More: it should be changed as soon as possible. It is saved in the System Keychain and, therefore, it is sure when the device is locked (as it should always be when not in use). The cloud storage (the real target of encryption) is always encrypted without any copy of the password. We feel this is the right balance between usability and security. Please note that attachments are not encrypted in any case." Version 1 synced by way of Dropbox. It is available at the Apple app stores.
It looks promising, but I have not tried it myself.