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| </pre><pre class="rust"><code><span class="comment">// Copyright 2018 Developers of the Rand project. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| </span><span class="doccomment">//! Random number generators and adapters |
| //! |
| //! ## Background: Random number generators (RNGs) |
| //! |
| //! Computers cannot produce random numbers from nowhere. We classify |
| //! random number generators as follows: |
| //! |
| //! - "True" random number generators (TRNGs) use hard-to-predict data sources |
| //! (e.g. the high-resolution parts of event timings and sensor jitter) to |
| //! harvest random bit-sequences, apply algorithms to remove bias and |
| //! estimate available entropy, then combine these bits into a byte-sequence |
| //! or an entropy pool. This job is usually done by the operating system or |
| //! a hardware generator (HRNG). |
| //! - "Pseudo"-random number generators (PRNGs) use algorithms to transform a |
| //! seed into a sequence of pseudo-random numbers. These generators can be |
| //! fast and produce well-distributed unpredictable random numbers (or not). |
| //! They are usually deterministic: given algorithm and seed, the output |
| //! sequence can be reproduced. They have finite period and eventually loop; |
| //! with many algorithms this period is fixed and can be proven sufficiently |
| //! long, while others are chaotic and the period depends on the seed. |
| //! - "Cryptographically secure" pseudo-random number generators (CSPRNGs) |
| //! are the sub-set of PRNGs which are secure. Security of the generator |
| //! relies both on hiding the internal state and using a strong algorithm. |
| //! |
| //! ## Traits and functionality |
| //! |
| //! All RNGs implement the [`RngCore`] trait, as a consequence of which the |
| //! [`Rng`] extension trait is automatically implemented. Secure RNGs may |
| //! additionally implement the [`CryptoRng`] trait. |
| //! |
| //! All PRNGs require a seed to produce their random number sequence. The |
| //! [`SeedableRng`] trait provides three ways of constructing PRNGs: |
| //! |
| //! - `from_seed` accepts a type specific to the PRNG |
| //! - `from_rng` allows a PRNG to be seeded from any other RNG |
| //! - `seed_from_u64` allows any PRNG to be seeded from a `u64` insecurely |
| //! - `from_entropy` securely seeds a PRNG from fresh entropy |
| //! |
| //! Use the [`rand_core`] crate when implementing your own RNGs. |
| //! |
| //! ## Our generators |
| //! |
| //! This crate provides several random number generators: |
| //! |
| //! - [`OsRng`] is an interface to the operating system's random number |
| //! source. Typically the operating system uses a CSPRNG with entropy |
| //! provided by a TRNG and some type of on-going re-seeding. |
| //! - [`ThreadRng`], provided by the [`thread_rng`] function, is a handle to a |
| //! thread-local CSPRNG with periodic seeding from [`OsRng`]. Because this |
| //! is local, it is typically much faster than [`OsRng`]. It should be |
| //! secure, though the paranoid may prefer [`OsRng`]. |
| //! - [`StdRng`] is a CSPRNG chosen for good performance and trust of security |
| //! (based on reviews, maturity and usage). The current algorithm is ChaCha12, |
| //! which is well established and rigorously analysed. |
| //! [`StdRng`] provides the algorithm used by [`ThreadRng`] but without |
| //! periodic reseeding. |
| //! - [`SmallRng`] is an **insecure** PRNG designed to be fast, simple, require |
| //! little memory, and have good output quality. |
| //! |
| //! The algorithms selected for [`StdRng`] and [`SmallRng`] may change in any |
| //! release and may be platform-dependent, therefore they should be considered |
| //! **not reproducible**. |
| //! |
| //! ## Additional generators |
| //! |
| //! **TRNGs**: The [`rdrand`] crate provides an interface to the RDRAND and |
| //! RDSEED instructions available in modern Intel and AMD CPUs. |
| //! The [`rand_jitter`] crate provides a user-space implementation of |
| //! entropy harvesting from CPU timer jitter, but is very slow and has |
| //! [security issues](https://github.com/rust-random/rand/issues/699). |
| //! |
| //! **PRNGs**: Several companion crates are available, providing individual or |
| //! families of PRNG algorithms. These provide the implementations behind |
| //! [`StdRng`] and [`SmallRng`] but can also be used directly, indeed *should* |
| //! be used directly when **reproducibility** matters. |
| //! Some suggestions are: [`rand_chacha`], [`rand_pcg`], [`rand_xoshiro`]. |
| //! A full list can be found by searching for crates with the [`rng` tag]. |
| //! |
| //! [`Rng`]: crate::Rng |
| //! [`RngCore`]: crate::RngCore |
| //! [`CryptoRng`]: crate::CryptoRng |
| //! [`SeedableRng`]: crate::SeedableRng |
| //! [`thread_rng`]: crate::thread_rng |
| //! [`rdrand`]: https://crates.io/crates/rdrand |
| //! [`rand_jitter`]: https://crates.io/crates/rand_jitter |
| //! [`rand_chacha`]: https://crates.io/crates/rand_chacha |
| //! [`rand_pcg`]: https://crates.io/crates/rand_pcg |
| //! [`rand_xoshiro`]: https://crates.io/crates/rand_xoshiro |
| //! [`rng` tag]: https://crates.io/keywords/rng |
| |
| </span><span class="attribute">#[cfg_attr(doc_cfg, doc(cfg(feature = <span class="string">"std"</span>)))] |
| #[cfg(feature = <span class="string">"std"</span>)] </span><span class="kw">pub mod </span>adapter; |
| |
| <span class="kw">pub mod </span>mock; <span class="comment">// Public so we don't export `StepRng` directly, making it a bit |
| // more clear it is intended for testing. |
| |
| </span><span class="attribute">#[cfg(all(feature = <span class="string">"small_rng"</span>, target_pointer_width = <span class="string">"64"</span>))] |
| </span><span class="kw">mod </span>xoshiro256plusplus; |
| <span class="attribute">#[cfg(all(feature = <span class="string">"small_rng"</span>, not(target_pointer_width = <span class="string">"64"</span>)))] |
| </span><span class="kw">mod </span>xoshiro128plusplus; |
| <span class="attribute">#[cfg(feature = <span class="string">"small_rng"</span>)] </span><span class="kw">mod </span>small; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std_rng"</span>)] </span><span class="kw">mod </span>std; |
| <span class="attribute">#[cfg(all(feature = <span class="string">"std"</span>, feature = <span class="string">"std_rng"</span>))] </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">mod </span>thread; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"small_rng"</span>)] </span><span class="kw">pub use </span><span class="self">self</span>::small::SmallRng; |
| <span class="attribute">#[cfg(feature = <span class="string">"std_rng"</span>)] </span><span class="kw">pub use </span><span class="self">self</span>::std::StdRng; |
| <span class="attribute">#[cfg(all(feature = <span class="string">"std"</span>, feature = <span class="string">"std_rng"</span>))] </span><span class="kw">pub use </span><span class="self">self</span>::thread::ThreadRng; |
| |
| <span class="attribute">#[cfg_attr(doc_cfg, doc(cfg(feature = <span class="string">"getrandom"</span>)))] |
| #[cfg(feature = <span class="string">"getrandom"</span>)] </span><span class="kw">pub use </span>rand_core::OsRng; |
| </code></pre></div> |
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