Implementation and optimization of ChaCha20 stream cipher on sunway taihuLight supercomputer

Data have always been the most valuable asset of enterprises and research institutions, and their confidentiality, especially the input and output data related to applications running on remote supercomputers, should be protected as much as possible. However, because of the large scale of the data, it takes a considerable amount of time to encrypt and decrypt them. The ChaCha20 cipher and the Advanced Encryption Standard (AES) cipher are the only ciphers supported by TLS v1.3. The ChaCha20 cipher is a kind of high-speed stream cipher emerging in recent years, which has attracted more and more attention due to its security and high efficiency. In order to make large-scale data en-/decryption more efficient, we implement a parallel version of the ChaCha20 stream cipher, parallel ChaCha20, which is optimized for SW26010 heterogeneous multi-core processor on the Sunway TaihuLight supercomputer. We used multiple optimization methods such as Direct Memory Access (DMA) and Single Instruction Multiple Data (SIMD) supported by SW26010 and proposed an optimization scheme that dynamically changes with the size of input data. The experiment results show that the parallel ChaCha20 has a maximum throughput of 32.43 GB/s on a single SW26010 processor, which is 2.4 times that of the best AES implementation on Sunway as far as we know. Moreover, the parallel ChaCha20 has a good scalability and runs on 1024 core groups with a max throughput of 8296.43 GB/s.