pub struct IsaacRng(/* private fields */);
Expand description
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 ↩
Implementations§
Source§impl IsaacRng
impl IsaacRng
Sourcepub fn new_from_u64(seed: u64) -> Self
👎Deprecated since 0.6.0: use SeedableRng::seed_from_u64 instead
pub fn new_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.
Trait Implementations§
Source§impl RngCore for IsaacRng
impl RngCore for IsaacRng
Source§fn fill_bytes(&mut self, dest: &mut [u8])
fn fill_bytes(&mut self, dest: &mut [u8])
dest
with random data. Read moreSource§impl SeedableRng for IsaacRng
impl SeedableRng for IsaacRng
Source§fn seed_from_u64(seed: u64) -> Self
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.
Auto Trait Implementations§
impl Freeze for IsaacRng
impl RefUnwindSafe for IsaacRng
impl Send for IsaacRng
impl Sync for IsaacRng
impl Unpin for IsaacRng
impl UnwindSafe for IsaacRng
Blanket Implementations§
Source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
Source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Source§impl<T> CloneToUninit for Twhere
T: Clone,
impl<T> CloneToUninit for Twhere
T: Clone,
Source§unsafe fn clone_to_uninit(&self, dst: *mut T)
unsafe fn clone_to_uninit(&self, dst: *mut T)
clone_to_uninit
)