Designing a secure DRAM+NVM hybrid memory module

Non-Volatile Memory (NVM) such as PCM has emerged as a potential alternative for main memory due to its high density and low leakage power. However, an NVM main-memory system faces three challenges when compared to Dynamic Random Access Memory (DRAM) - long latency, poor write endurance and data security. To address these three challenges, we propose a secure DRAM+NVM hybrid memory module. The hybrid module integrates a DRAM cache and a security unit (SU). DRAM cache can improve the performance of an NVM memory module and reduce the number of direct writes to the NVM. Our results show that a 256MB 2-way DRAM cache with a 1024B cache line performs well in an 8GB NVM main memory module. The SU is embedded in the onboard controller and includes an AES-GCM engine and an NVM vault. The AES-GCM engine implements encryption and authentication with low overhead. The NVM vault is used to store MAC tags and counter values for each DRAM cache line. According to our results, the proposed secure hybrid memory module improves the performance by 32% compared to an NVM-only memory module, and is only 6.8% slower than a DRAM only memory module.