$\mathcal{F}lush+early\mathcal{R}\text{ELOAD}$: Covert Channels Attack on Shared LLC Using MSHR Merging

Modern multiprocessors include multiple cores, all of them share a large Last Level Cache (LLC). Because of the shared nature of LLC, different timing channel attacks can be built by exploiting LLC behaviors. Covert Channel and Side Channel are two well-known attacks used to steal sensitive information from a secure application. While several countermeasures have already been proposed to prevent these attacks, the possibility of discovering new variants cannot be overlooked. In this paper, we propose a covert channel attack designed to circumvent the state-of-the-art countermeasure for preventing the Flush+Reload attack. Experimental results indicate that the proposed attack renders the current state-of-the-art countermeasure futile and ineffective.