Pipelined Hardware Implementation of COPA, ELmD, and COLM

Authenticated encryption algorithms offer privacy, authentication, and data integrity, as well. In recent years, they have received special attention after the call for submissions of Competition for Authenticated Encryption: Security, Applicability, and Robustness (CAESAR) was published. The CAESAR goal is to generate a portfolio with recommendations of authenticated encryption algorithms for three different scenarios: Lightweight, high speed, and defense in deep. ELmD and COPA are two on-line authenticated encryption algorithms submitted to CAESAR; because of their similarities, they were merged as COLM during the third-round of CAESAR. COLM is a finalist in the use case 3 defense in depth. ELmD, COPA, and COLM are based on the ECB-mix-ECB structure, which is highly parallelizable and pipelineable. In this paper, we present optimized single-chip implementations of ELmD, COPA, and COLM using pipelining. For ELmD, we present implementations for eight combinations of its parameters set: For intermediate tags, fixed, variable tag length, and 10 and 6 AES rounds. COLM implementation is for variable tag length without intermediate tags. In the case of COPA, it does not have parameters set. The implementation results with a Xilinx Virtex 6 FPGA show that ELmD is the best option concerning area and speed for single-chip implementation. The area of COPA and COLM are 1.65 and 1.69 times ELmD's respectively. Regarding throughput, the range of our implementations goes from 33.34 Gbits/s for COLM to more than 35 Gbits/s for several versions of ELmD.