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.

Multicore systems with shared Last Level Cache (LLC) possess a bigger challenge in allocating the LLC space among multiple applications running in the system. Since all applications use the shared LLC, interference caused by them may evict important blocks of other applications that result in premature eviction and may also lead to thrashing. Replacement policies applied locally to a set distributes the sets in a dynamic way among the applications. However, previous work on replacement techniques focused on the re-reference aspect of a block or application behavior to improve the overall system performance. The paper proposes a novel cache replacement technique Application Aware Re-reference Interval Prediction (AARIP) that considers application behavior, re-reference interval, and premature block eviction for replacing a cache block. Experimental evaluation on a four-core system shows that AARIP achieves an overall performance improvement of 7.28%, throughput by 4.9%, and improves overall system fairness by 7.85%, as compared to the traditional SRRIP replacement policy.