# README
fastrand
go get github.com/uplo-tech/fastrand
fastrand implements a cryptographically secure pseudorandom number generator.
The generator is seeded using the system's default entropy source, and
thereafter produces random values via repeated hashing. As a result, fastrand
can generate randomness much faster than crypto/rand, and generation cannot
fail beyond a potential panic during init().
fastrand also scales better than crypto/rand and math/rand when called in
parallel. In fact, fastrand can even outperform math/rand when using enough threads.
Benchmarks
// 32 byte reads
BenchmarkRead32 10000000 175 ns/op 181.86 MB/s
BenchmarkReadCrypto32 500000 2733 ns/op 11.71 MB/s
// 512 kb reads
BenchmarkRead512kb 1000 1336217 ns/op 383.17 MB/s
BenchmarkReadCrypto512kb 50 33423693 ns/op 15.32 MB/s
// 32 byte reads using 4 threads
BenchmarkRead4Threads32 3000000 392 ns/op 326.46 MB/s
BenchmarkReadCrypto4Threads32 200000 7579 ns/op 16.89 MB/s
// 512 kb reads using 4 threads
BenchmarkRead4Threads512kb 1000 1899048 ns/op 1078.43 MB/s
BenchmarkReadCrypto4Threads512kb 20 97423380 ns/op 21.02 MB/s
Security
fastrand uses an algorithm similar to Fortuna, which is the basis for the
/dev/random device in FreeBSD. However, although the techniques used by
fastrand are known to be secure, the specific implementation has not been
reviewed by a security professional. Use with caution.
The general strategy is to use crypto/rand at init to get 32 bytes of strong
entropy. From there, the entropy is concatenated to a counter and hashed
repeatedly, providing 64 bytes of random output each time the counter is
incremented. The counter is 16 bytes, which provides strong guarantees that a
cycle will not be seen throughout the lifetime of the program.
The sync/atomic package is used to ensure that multiple threads calling
fastrand concurrently are always guaranteed to end up with unique counters.