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fastrand
--------
[](https://godoc.org/github.com/NebulousLabs/fastrand)
[](https://goreportcard.com/report/github.com/NebulousLabs/fastrand)
```
go get github.com/NebulousLabs/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.
|
