ChaCha20 and XChaCha20 stream ciphers go library

 The ChaCha20 stream cipher ChaCha is a stream cipher family
 created by Daniel J. Bernstein. The most common ChaCha cipher
 is ChaCha20 (20 rounds). ChaCha20 is standardized in RFC 7539
 (https://tools.ietf.org/html/rfc7539).
 .
 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 subpackage 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.