[−][src]Struct rand_jitter::JitterRng
A true random number generator based on jitter in the CPU execution time, and jitter in memory access time.
Note that this RNG is not suitable for use cases where cryptographic security is required.
Implementations
impl<F> JitterRng<F> where
F: Fn() -> u64 + Send + Sync,
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F: Fn() -> u64 + Send + Sync,
pub fn new_with_timer(timer: F) -> JitterRng<F>
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Create a new JitterRng
.
A custom timer can be supplied, making it possible to use JitterRng
in
no_std
environments.
The timer must have nanosecond precision.
This method is more low-level than new()
. It is the responsibility of
the caller to run test_timer
before using any numbers generated with
JitterRng
, and optionally call set_rounds
. Also it is important to
consume at least one u64
before using the first result to initialize
the entropy collection pool.
Example
use rand_jitter::JitterRng; fn get_nstime() -> u64 { use std::time::{SystemTime, UNIX_EPOCH}; let dur = SystemTime::now().duration_since(UNIX_EPOCH).unwrap(); // The correct way to calculate the current time is // `dur.as_secs() * 1_000_000_000 + dur.subsec_nanos() as u64` // But this is faster, and the difference in terms of entropy is // negligible (log2(10^9) == 29.9). dur.as_secs() << 30 | dur.subsec_nanos() as u64 } let mut rng = JitterRng::new_with_timer(get_nstime); let rounds = rng.test_timer()?; rng.set_rounds(rounds); // optional let _ = rng.next_u64(); // Ready for use let v: u64 = rng.next_u64();
pub fn set_rounds(&mut self, rounds: u8)
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Configures how many rounds are used to generate each 64-bit value. This must be greater than zero, and has a big impact on performance and output quality.
new_with_timer
conservatively uses 64 rounds, but often less rounds
can be used. The test_timer()
function returns the minimum number of
rounds required for full strength (platform dependent), so one may use
rng.set_rounds(rng.test_timer()?);
or cache the value.
pub fn test_timer(&mut self) -> Result<u8, TimerError>
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Basic quality tests on the timer, by measuring CPU timing jitter a few hundred times.
If successful, this will return the estimated number of rounds necessary
to collect 64 bits of entropy. Otherwise a TimerError
with the cause
of the failure will be returned.
pub fn timer_stats(&mut self, var_rounds: bool) -> i64
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Statistical test: return the timer delta of one normal run of the
JitterRng
entropy collector.
Setting var_rounds
to true
will execute the memory access and the
CPU jitter noice sources a variable amount of times (just like a real
JitterRng
round).
Setting var_rounds
to false
will execute the noice sources the
minimal number of times. This can be used to measure the minimum amount
of entropy one round of the entropy collector can collect in the worst
case.
See this crate's README on how to use timer_stats
to test the quality
of JitterRng
.
Trait Implementations
impl<F> Clone for JitterRng<F> where
F: Clone,
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F: Clone,
fn clone(&self) -> JitterRng<F>
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fn clone_from(&mut self, source: &Self)
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impl<F> Debug for JitterRng<F>
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impl<F> RngCore for JitterRng<F> where
F: Fn() -> u64 + Send + Sync,
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F: Fn() -> u64 + Send + Sync,
fn next_u32(&mut self) -> u32
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fn next_u64(&mut self) -> u64
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fn fill_bytes(&mut self, dest: &mut [u8])
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fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>
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Auto Trait Implementations
impl<F> Send for JitterRng<F> where
F: Send,
F: Send,
impl<F> Sync for JitterRng<F> where
F: Sync,
F: Sync,
impl<F> Unpin for JitterRng<F> where
F: Unpin,
F: Unpin,
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,