The disclosed technology includes techniques for improving data privacy in mobile communications over public cloud services. According to certain implementations, a novel conceptual layer may be interposed between the “application” layer and the “user” layer. In some implementations, the conceptual layer may be at least partially embodied by a transparent window or pane overlaid on top of existing app graphical user interfaces to: (1) intercept plaintext user input before transforming the input and feeding it to an underlying app; and (2) reverse transform output data from the app before displaying the plaintext data to the user. Accordingly, the conceptual layer may serve as a protective layer while preserving the original application workflow and look-and-feel.