Struct rand_isaac::isaac64::Isaac64Rng

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pub struct Isaac64Rng(BlockRng64<Isaac64Core>);
Expand description

A random number generator that uses ISAAC-64, the 64-bit variant of 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 19961.

ISAAC-64 is mostly similar to ISAAC. Because it operates on 64-bit integers instead of 32-bit, it uses twice as much memory to hold its state and results. Also it uses different constants for shifts and indirect indexing, optimized to give good results for 64bit arithmetic.

ISAAC-64 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 from the rand_hc crate instead, which, like ISAAC, is an array-based RNG and one of the stream-ciphers selected the by eSTREAM

§Overview of the ISAAC-64 algorithm:

(in pseudo-code)

Input: a, b, c, s[256] // state
Output: r[256] // results

mix(a,i) = !(a ^ a << 21)  if i = 0 mod 4
             a ^ a >>  5   if i = 1 mod 4
             a ^ a << 12   if i = 2 mod 4
             a ^ a >> 33   if i = 3 mod 4

c = c + 1
b = b + c

for i in 0..256 {
    x = s_[i]
    a = mix(a,i) + s[i+128 mod 256]
    y = a + b + s[x>>3 mod 256]
    s[i] = y
    b = x + s[y>>11 mod 256]
    r[i] = b
}

This implementation uses BlockRng64 to implement the RngCore methods.

See for more information the documentation of IsaacRng.


  1. Bob Jenkins, ISAAC and RC4 

Tuple Fields§

§0: BlockRng64<Isaac64Core>

Trait Implementations§

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impl Clone for Isaac64Rng

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fn clone(&self) -> Isaac64Rng

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for Isaac64Rng

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

Formats the value using the given formatter. Read more
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impl RngCore for Isaac64Rng

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fn next_u32(&mut self) -> u32

Return the next random u32. Read more
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fn next_u64(&mut self) -> u64

Return the next random u64. Read more
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fn fill_bytes(&mut self, dest: &mut [u8])

Fill dest with random data. Read more
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fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>

Fill dest entirely with random data. Read more
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impl SeedableRng for Isaac64Rng

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fn seed_from_u64(seed: u64) -> Self

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.

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type Seed = <Isaac64Core as SeedableRng>::Seed

Seed type, which is restricted to types mutably-dereferenceable as u8 arrays (we recommend [u8; N] for some N). Read more
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fn from_seed(seed: Self::Seed) -> Self

Create a new PRNG using the given seed. Read more
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fn from_rng<S: RngCore>(rng: S) -> Result<Self, Error>

Create a new PRNG seeded from another Rng. Read more
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fn from_entropy() -> Self

Creates a new instance of the RNG seeded via getrandom. Read more

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.