ACPC: Covert Channel Attack on Last Level Cache using Dynamic Cache Partitioning

Abstract

The Last Level Cache (LLC) of modern multicore processors is normally shared between different cores and applications. Dynamic cache partitioning is applied to the LLC for fairly distributing the LLC space among the applications. Recently, Covert Channel Attacks (CCA) becomes a major security issue for modern multicore systems. In CCA, two malicious applications: spy and Trojan, run in two different cores. Trojan normally runs in a secure core and knows some secret information. Through CCA, Trojan communicates this information to the spy. A well-known technique to perform such an attack is Prime Probe (P+P). It performs the attack by using the shared behavior of LLC space. Cache partitioning is considered a defense against such CCA. Partitioning makes the applications isolated in the LLC and they cannot evict each other block from the LLC. Hence, the existing P+P based attacks are not possible while dynamic partitioning is applied to LLC. However, in this work, we have proposed a modified CCA (based on P+P) which can establish a covert channel on top of the dynamic cache partitioning technique applied to LLC. Such kinds of attacks must need to be handled carefully in modern processors. A possible defense mechanism for the new attack is also discussed in this paper.