Struct rand::rngs::EntropyRng[][src]

pub struct EntropyRng { /* fields omitted */ }

An interface returning random data from external source(s), provided specifically for securely seeding algorithmic generators (PRNGs).

Where possible, EntropyRng retrieves random data from the operating system's interface for random numbers (OsRng); if that fails it will fall back to the JitterRng entropy collector. In the latter case it will still try to use OsRng on the next usage.

If no secure source of entropy is available EntropyRng will panic on use; i.e. it should never output predictable data.

This is either a little slow (OsRng requires a system call) or extremely slow (JitterRng must use significant CPU time to generate sufficient jitter); for better performance it is common to seed a local PRNG from external entropy then primarily use the local PRNG (thread_rng is provided as a convenient, local, automatically-seeded CSPRNG).


On most systems, like Windows, Linux, macOS and *BSD on common hardware, it is highly unlikely for both OsRng and JitterRng to fail. But on combinations like webassembly without Emscripten or stdweb both sources are unavailable. If both sources fail, only try_fill_bytes is able to report the error, and only the one from OsRng. The other RngCore methods will panic in case of an error.


impl EntropyRng

Create a new EntropyRng.

This method will do no system calls or other initialization routines, those are done on first use. This is done to make new infallible, and try_fill_bytes the only place to report errors.

Trait Implementations

impl Debug for EntropyRng

Formats the value using the given formatter. Read more

impl Default for EntropyRng

Returns the "default value" for a type. Read more

impl RngCore for EntropyRng

Return the next random u32. Read more

Return the next random u64. Read more

Fill dest with random data. Read more

Fill dest entirely with random data. Read more

impl CryptoRng for EntropyRng

Auto Trait Implementations

impl Send for EntropyRng

impl Sync for EntropyRng