Reducing the Overhead of Authenticated Memory Encryption Using Delta Encoding and ECC Memory

Data stored in an off-chip memory, such as DRAM or non-volatile main memory, can potentially be extracted or tampered by an attacker with physical access to a device. Protecting such attacks requires storing message authentication codes and counters which incur a 22% storage overhead. In this work, we propose techniques for reducing these overheads. We first present a scheme that leverages ECC DRAMs to reduce MAC verification & storage overheads. We replace the parity bits in standard ECC by a combination of MAC and parity bits to provide both authentication and error correction. This eliminates the extra MAC storage and minimizes the verification overhead as MACs can be read in parallel with data through the ECC bus. Next, we use efficient integer encodings to reduce counter storage overhead by 6x while enhancing application performance.