[−][src]Struct rand_isaac::isaac::IsaacRng
A random number generator that uses the ISAAC algorithm.
ISAAC stands for "Indirection, Shift, Accumulate, Add, and Count" which are the principal bitwise operations employed. It is the most advanced of a series of array based random number generator designed by Robert Jenkins in 199612.
ISAAC is notably fast and produces excellent quality random numbers for non-cryptographic applications.
In spite of being designed with cryptographic security in mind, ISAAC hasn't
been stringently cryptanalyzed and thus cryptographers do not not
consensually trust it to be secure. When looking for a secure RNG, prefer
Hc128Rng
instead, which, like ISAAC, is an array-based RNG and one of
the stream-ciphers selected the by eSTREAM contest.
In 2006 an improvement to ISAAC was suggested by Jean-Philippe Aumasson, named ISAAC+3. But because the specification is not complete, because there is no good implementation, and because the suggested bias may not exist, it is not implemented here.
Overview of the ISAAC algorithm:
(in pseudo-code)
Input: a, b, c, s[256] // state
Output: r[256] // results
mix(a,i) = a ^ a << 13 if i = 0 mod 4
a ^ a >> 6 if i = 1 mod 4
a ^ a << 2 if i = 2 mod 4
a ^ a >> 16 if i = 3 mod 4
c = c + 1
b = b + c
for i in 0..256 {
x = s_[i]
a = f(a,i) + s[i+128 mod 256]
y = a + b + s[x>>2 mod 256]
s[i] = y
b = x + s[y>>10 mod 256]
r[i] = b
}
Numbers are generated in blocks of 256. This means the function above only runs once every 256 times you ask for a next random number. In all other circumstances the last element of the results array is returned.
ISAAC therefore needs a lot of memory, relative to other non-crypto RNGs. 2 * 256 * 4 = 2 kb to hold the state and results.
This implementation uses BlockRng
to implement the RngCore
methods.
References
Bob Jenkins, ISAAC: A fast cryptographic random number generator ↩
Bob Jenkins, ISAAC and RC4 ↩
Jean-Philippe Aumasson, On the pseudo-random generator ISAAC ↩
Methods
impl IsaacRng
[src]
pub fn new_from_u64(seed: u64) -> Self
[src]
use SeedableRng::seed_from_u64 instead
Create an ISAAC random number generator using an u64
as seed.
If seed == 0
this will produce the same stream of random numbers as
the reference implementation when used unseeded.
Trait Implementations
impl Debug for IsaacRng
[src]
impl Clone for IsaacRng
[src]
impl SeedableRng for IsaacRng
[src]
type Seed = <IsaacCore as SeedableRng>::Seed
Seed type, which is restricted to types mutably-dereferencable as u8
arrays (we recommend [u8; N]
for some N
). Read more
fn from_seed(seed: Self::Seed) -> Self
[src]
fn seed_from_u64(seed: u64) -> Self
[src]
Create an ISAAC random number generator using an u64
as seed.
If seed == 0
this will produce the same stream of random numbers as
the reference implementation when used unseeded.
fn from_rng<S: RngCore>(rng: S) -> Result<Self, Error>
[src]
impl RngCore for IsaacRng
[src]
Auto Trait Implementations
impl Unpin for IsaacRng
impl Send for IsaacRng
impl Sync for IsaacRng
impl UnwindSafe for IsaacRng
impl RefUnwindSafe for IsaacRng
Blanket Implementations
impl<T> From<T> for T
[src]
impl<T, U> TryFrom<U> for T where
U: Into<T>,
[src]
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>
[src]
impl<T, U> Into<U> for T where
U: From<T>,
[src]
U: From<T>,
impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
[src]
U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
[src]
impl<T> Borrow<T> for T where
T: ?Sized,
[src]
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]
T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
[src]
impl<T> Any for T where
T: 'static + ?Sized,
[src]
T: 'static + ?Sized,
impl<T> ToOwned for T where
T: Clone,
[src]
T: Clone,