Hiding Information in Flash Memory

This paper introduces a novel information hiding technique for Flash memory. The method hides data within an analog characteristic of Flash, the program time of individual bits. Because the technique uses analog behaviors, normal Flash memory operations are not affected and hidden information is invisible in the data stored in the memory. Even if an attacker checks a Flash chip's analog characteristics, experimental results indicate that the hidden information is difficult to distinguish from inherent manufacturing variation or normal wear on the device. Moreover, the hidden data can survive erasure of the Flash memory data, and the technique can be used on current Flash chips without hardware changes.