The ChaCha20 stream cipher

ChaCha is a stream cipher family created by Daniel J. Bernstein.
The most common ChaCha variant is ChaCha20 (20 rounds). ChaCha20 is standardized in RFC 7539.

This package provides implementations of three ChaCha versions:

• ChaCha20 with a 64 bit nonce (can en/decrypt up to 2^64 * 64 bytes for one key-nonce combination)
• ChaCha20 with a 96 bit nonce (can en/decrypt up to 2^32 * 64 bytes ~ 256 GB for one key-nonce combination)
• XChaCha20 with a 192 bit nonce (can en/decrypt up to 2^64 * 64 bytes for one key-nonce combination)

Furthermore the chacha sub package implements ChaCha20/12 and ChaCha20/8. These versions use 12 or 8 rounds instead of 20. But it's recommended to use ChaCha20 (with 20 rounds) - it will be fast enough for almost all purposes.

Installation

Install in your GOPATH: go get -u github.com/aead/chacha20

Requirements

All go versions >= 1.8.7 are supported. The code may also work on Go 1.7 but this is not tested.

Performance

AMD64

Hardware: Intel i7-6500U 2.50GHz x 2
System: Linux Ubuntu 16.04 - kernel: 4.4.0-62-generic
Go version: 1.8.0

AVX2
name                        speed              cpb
ChaCha20_64-4                573MB/s ± 0%      4.16
ChaCha20_1K-4               2.19GB/s ± 0%      1.06
XChaCha20_64-4               261MB/s ± 0%      9.13
XChaCha20_1K-4              1.69GB/s ± 4%      1.37
XORKeyStream64-4             474MB/s ± 2%      5.02
XORKeyStream1K-4            2.09GB/s ± 1%      1.11
XChaCha20_XORKeyStream64-4   262MB/s ± 0%      9.09
XChaCha20_XORKeyStream1K-4  1.71GB/s ± 1%      1.36

SSSE3
name                        speed              cpb
ChaCha20_64-4                583MB/s ± 0%      4.08
ChaCha20_1K-4               1.15GB/s ± 1%      2.02
XChaCha20_64-4               267MB/s ± 0%      8.92
XChaCha20_1K-4               984MB/s ± 5%      2.42
XORKeyStream64-4             492MB/s ± 1%      4.84
XORKeyStream1K-4            1.10GB/s ± 5%      2.11
XChaCha20_XORKeyStream64-4   266MB/s ± 0%      8.96
XChaCha20_XORKeyStream1K-4  1.00GB/s ± 2%      2.32

386

Hardware: Intel i7-6500U 2.50GHz x 2
System: Linux Ubuntu 16.04 - kernel: 4.4.0-62-generic
Go version: 1.8.0

SSSE3
name                        speed              cpb
ChaCha20_64-4               570MB/s ± 0%       4.18
ChaCha20_1K-4               650MB/s ± 0%       3.66
XChaCha20_64-4              223MB/s ± 0%      10.69
XChaCha20_1K-4              584MB/s ± 1%       4.08
XORKeyStream64-4            392MB/s ± 1%       6.08
XORKeyStream1K-4            629MB/s ± 1%       3.79
XChaCha20_XORKeyStream64-4  222MB/s ± 0%      10.73
XChaCha20_XORKeyStream1K-4  585MB/s ± 0%       4.07

SSE2
name                        speed              cpb
ChaCha20_64-4               509MB/s ± 0%       4.68
ChaCha20_1K-4               553MB/s ± 2%       4.31
XChaCha20_64-4              201MB/s ± 0%      11.86
XChaCha20_1K-4              498MB/s ± 4%       4.78
XORKeyStream64-4            359MB/s ± 1%       6.64
XORKeyStream1K-4            545MB/s ± 0%       4.37
XChaCha20_XORKeyStream64-4  201MB/s ± 1%      11.86
XChaCha20_XORKeyStream1K-4  507MB/s ± 0%       4.70