Is it approximate computing or malicious computing?

Approximate computing (AC) is an attractive energy efficient technique that can be implemented at almost all the design levels including data, algorithm, and hardware. The basic idea behind AC is to deliberately control the trade-off between computation accuracy and energy efficiency. However, with the introduction of AC, traditional computing frameworks are having many potential security vulnerabilities. In this paper, we analyze these vulnerabilities and the associated attacks as well as corresponding countermeasures. More importantly, we propose the vulnerability at data level and demonstrate that without appropriate security mechanism, adversaries can modify the data and convert a secure and trusted AC process to one that produces unexpected errors in the final output. Furthermore, it is difficult to distinguish whether such errors are caused by the approximation nature of AC or from malicious modification and injection. Finally, we propose the information hiding based countermeasures to defend against both existing attacks and the proposed data level attacks, which helps to answer the question: given an error in AC, whether it comes from approximation or it is maliciously introduced.