A Refresh-Free Near-eDRAM AES Accelerator for Secure Underwater Communications

Underwater vehicles or drones need to encrypt and transmit data to protect the information from external attacks. However, these electronic devices in underwater vehicles operate under limited energy. Therefore, a low-energy cryptographic accelerator is needed so that it can operate for a longer period on a single energy charge. In this paper, we present a compact and energy-efficient eDRAM-based AES encryption engine, named SwiftGuard, exploiting the nature of frequent state updates of the AES algorithm and the benefit of dual-port eDRAM design. By updating the data block within the data retention time of designed eDRAM bitcells, SwiftGuard removes expensive memory refresh operations during AES computations. In addition, the AES latency is greatly reduced by leveraging simultaneous read and write operations of the dual-port eDRAM design. Last but not least, it improves the area efficiency by sharing an on-the-fly key expansion module and using logic-based S-boxes. As a result, SwiftGuard occupies 38 % less area and achieves 54 % (or 42 %) higher performance (or energy efficiency) compared to the state-of-the-art SRAM-based AES accelerator.