Struct rand::chacha::ChaChaRng

[+] Show declaration

pub struct ChaChaRng { /* fields omitted */ }

[−] Expand description

A random number generator that uses the ChaCha20 algorithm [1].

The ChaCha algorithm is widely accepted as suitable for cryptographic purposes, but this implementation has not been verified as such. Prefer a generator like OsRng that defers to the operating system for cases that need high security.

[1]: D. J. Bernstein, ChaCha, a variant of Salsa20

Methods

impl ChaChaRng

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pub fn new_unseeded() -> ChaChaRng

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Create an ChaCha random number generator using the default fixed key of 8 zero words.

Examples

use rand::{Rng, ChaChaRng};

let mut ra = ChaChaRng::new_unseeded();
println!("{:?}", ra.next_u32());
println!("{:?}", ra.next_u32());

Since this equivalent to a RNG with a fixed seed, repeated executions of an unseeded RNG will produce the same result. This code sample will consistently produce:

• 2917185654
• 2419978656

pub fn set_counter(&mut self, counter_low: u64, counter_high: u64)

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Sets the internal 128-bit ChaCha counter to a user-provided value. This permits jumping arbitrarily ahead (or backwards) in the pseudorandom stream.

Since the nonce words are used to extend the counter to 128 bits, users wishing to obtain the conventional ChaCha pseudorandom stream associated with a particular nonce can call this function with arguments 0, desired_nonce.

Examples

use rand::{Rng, ChaChaRng};

let mut ra = ChaChaRng::new_unseeded();
ra.set_counter(0u64, 1234567890u64);
println!("{:?}", ra.next_u32());
println!("{:?}", ra.next_u32());

Trait Implementations

impl Rng for ChaChaRng

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fn next_u32(&mut self) -> u32

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Return the next random u32.

fn next_u64(&mut self) -> u64

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Return the next random u64.

fn next_f32(&mut self) -> f32

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Return the next random f32 selected from the half-open interval [0, 1).

fn next_f64(&mut self) -> f64

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Return the next random f64 selected from the half-open interval [0, 1).

fn fill_bytes(&mut self, dest: &mut [u8])

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Fill dest with random data.

fn gen<T>(&mut self) -> T where     T: Rand,

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Return a random value of a Rand type.

Important traits for Generator<'a, T, R>

impl<'a, T, R> Iterator for Generator<'a, T, R> where
    R: Rng,
    T: Rand,  type Item = T;

fn gen_iter<T>(&'a mut self) -> Generator<'a, T, Self> where     T: Rand,

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Return an iterator that will yield an infinite number of randomly generated items.

fn gen_range<T>(&mut self, low: T, high: T) -> T where     T: SampleRange + PartialOrd<T>,

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Generate a random value in the range [low, high).

fn gen_weighted_bool(&mut self, n: u32) -> bool

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Return a bool with a 1 in n chance of true

Important traits for AsciiGenerator<'a, R>

impl<'a, R> Iterator for AsciiGenerator<'a, R> where
    R: Rng,  type Item = char;

fn gen_ascii_chars(&'a mut self) -> AsciiGenerator<'a, Self>

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Return an iterator of random characters from the set A-Z,a-z,0-9.

fn choose<T>(&mut self, values: &'a [T]) -> Option<&'a T>

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Return a random element from values.

fn choose_mut<T>(&mut self, values: &'a mut [T]) -> Option<&'a mut T>

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Return a mutable pointer to a random element from values.

fn shuffle<T>(&mut self, values: &mut [T])

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Shuffle a mutable slice in place.

impl Rand for ChaChaRng

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fn rand<R>(other: &mut R) -> ChaChaRng where     R: Rng,

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Generates a random instance of this type using the specified source of randomness.

impl Copy for ChaChaRng

impl Clone for ChaChaRng

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fn clone(&self) -> ChaChaRng

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Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

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Performs copy-assignment from source.

impl<'a> SeedableRng<&'a [u32]> for ChaChaRng

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fn reseed(&mut self, seed: &'a [u32])

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Reseed an RNG with the given seed.

fn from_seed(seed: &'a [u32]) -> ChaChaRng

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Create a ChaCha generator from a seed, obtained from a variable-length u32 array. Only up to 8 words are used; if less than 8 words are used, the remaining are set to zero.

impl Debug for ChaChaRng

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fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

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Formats the value using the given formatter.