allout-encrypt-unencrypted-on-saves is a variable defined in `allout.el'.
Its value is

  • Automatically becomes buffer-local when set.

If non-nil, topics pending encryption are encrypted during buffer saves.

This prevents file-system exposure of un-encrypted contents of
items marked for encryption.

When non-nil, if the topic currently being edited is decrypted,
it will be encrypted for saving but automatically decrypted
before any subsequent user interaction, so it is once again clear
text for editing though the file system copy is encrypted.

(Auto-saves are handled differently. Buffers with plain-text
exposed encrypted topics are exempted from auto saves until all
such topics are encrypted.)

You can customize this variable.

This variable was introduced, or its default value was changed, in version 23.1 of Emacs.