'Although password protection improves the security of your personal information by making it harder for other people to read your notes without your permission, it is not a foolproof safeguard. If you forget your password, no one will be able to unlock your notes for you - not even Microsoft Technical Support.” “OneNote for Mac uses 128-bit AES encryption to secure password-protected notebook sections. Microsoft's statement on using OneNote 2016 for Mac with 128 bit AES is. OneNote 2016 uses 128bit AES for encrypting notebook 'sections' (this is for the Mac version which is most relevant for me).

This ensures that the sync will only happen after you've encrypted the text. If you're going to go this route and use Evernote's servers instead of local notebooks I would suggest turning the auto sync function off, and only allowing your notebooks to be manually synced by using the sync button. Images, and whatever else may be in the note are not able to be encrypted. Evernote's encryption implementation is 128 bit AES and only allows users to encrypt excerpts of text inside of a note instead of encrypting the entire note meaning that only the highlighted text is encrypted.

Keep vs evernote vs onenote