Key Highlights

High-level problem addressed

Electronic devices are increasingly the subject of inspection by authorities. While encryption hides secret messages, it does not hide the transmission of those secret messages---in fact, it calls attention to them. This work designs a steganograph that hides information "underneath" system data.

Main contribution

This paper unveils Invisible Bits a new steganographic technique that hides secret messages in the analog domain of Static Random Access Memory (SRAM) embedded within a computing device.

Results

Experiments with commercial devices show that Invisible Bits provides over 90% capacity two orders-of-magnitude more than previous on-chip steganographic approaches, while retaining device functionality even when the device undergoes subsequent normal operation or is shelved for months. Experiments also show that adversaries cannot differentiate between devices with encoded messages and those without.

Significance and industrial relevance

Invisible bits show how on-chip SRAM can carry stealthy information along with the system data. The idea can be used in the post-production watermarking of devices.

Acquired technical skills

Expertise in SoC subsystem power distribution, low-level firmware modification, modeling circuit behavior in SPICE, executing stress tests, and developing efficient cryptographic protocols in low-level hardware where high-level library support is rare.