Optimized Galois-Counter-Mode Implementation on Intel® Architecture Processors

Executive Summary Galois-Counter-Mode (GCM) is a block cipher mode of operation that uses universal hashing over a binary Galois field to provide authenticated encryption. Galois Hash is used for authentication, and the Advanced Encryption Standard (AES) block cipher is used for encryption in counter mode of operation. This paper describes an optimized implementation of GCM benefiting from the PCLMULQDQ instruction and AES-NI set of instructions on Intel ® processors based on the 32-nm microarchitecture. This paper describes an optimized implementation of GCM that combines function stitching with novel polynomial multiplication methods. We are able to achieve performance of ~ 2.8 Cycles/byte on large buffers, on a single core of an Intel ® Core™ i5 650 processor, with Intel ® Hyper-Threading Technology. This represents a new record for GCM performance on Intel ® processors.