Abstract: Approximate computing circuits are designed for applications with inherent error tolerance.By sacrificing a certain degree of computational accuracy,they achieve advantages in computational performance and energy efficiency.However,recent studies have pointed out that the approximation mechanisms of approximate computing circuits may be exploited to create new attacks.The exploration of attack instances and corresponding detection or protection methods is gradually attracting widespread attention.So far,the investigation into the security threats of approximate computing circuits is still in its early stages.Only a few studies have proposed specific attack examples,and there is a lack of research on attack patterns and protective measures for configurable approximate adders.Therefore,there is an urgent need to investigate existing configurable approximate adders and propose possible attack methods to reveal new security threats.This paper proposes an approximate-precise boundary (APB) attack targeting configurable approximate adders and analyzes two attack modes.In addition, two protective measures,namely approximate types random selection and approximate configuration authorization circuits, are proposed.Experimental results show that the approximate configuration authorization circuit can protect against attacks with an additional area overhead of 10.17%,an additional power consumption overhead of less than 13%,and negligible additional delay overhead.

Key words: approximate computing circuit, hardware security, image processing, approximate types random select, approximate configuration authorization