#[derive(Copy)]
pub struct Hc256Rng {
p: [u32; 1024],
q: [u32; 1024],
c: usize
}
impl Clone for Hc256Rng { fn clone(&self) -> Hc256Rng { *self } }
impl Hc256Rng {
pub fn init(key: &[u32; 8], iv: &[u32; 8]) -> Hc256Rng {
let mut w = [0; 2560];
w[..8].copy_from_slice(key);
w[8..16].copy_from_slice(iv);
Self::with_w(&mut w)
}
pub fn with_w(w: &mut [u32; 2560]) -> Hc256Rng {
let mut hc256 = Hc256Rng {
p: [0; 1024],
q: [0; 1024],
c: 0
};
for i in 16..2560 {
w[i] = f2(w[i - 2])
.wrapping_add(w[i - 7])
.wrapping_add(f1(w[i - 15]))
.wrapping_add(w[i - 16])
.wrapping_add(i as u32);
}
hc256.p.copy_from_slice(&w[512..1536]);
hc256.q.copy_from_slice(&w[1536..]);
for _ in 0..4096 {
hc256.gen();
}
hc256
}
pub fn gen(&mut self) -> u32 {
let i = self.c & 0x3ff;
let i3 = i.wrapping_sub(3) & 0x3ff;
let i10 = i.wrapping_sub(10) & 0x3ff;
let i12 = i.wrapping_sub(12) & 0x3ff;
let i1023 = i.wrapping_sub(1023) & 0x3ff;
let output = if self.c < 1024 {
self.p[i] = self.p[i]
.wrapping_add(self.p[i10])
.wrapping_add(self.p[i3].rotate_right(10) ^ self.p[i1023].rotate_right(23))
.wrapping_add(self.q[(self.p[i3] ^ self.p[i1023]) as usize & 0x3ff]);
h(&self.q, self.p[i12]) ^ self.p[i]
} else {
self.q[i] = self.q[i]
.wrapping_add(self.q[i10])
.wrapping_add(self.q[i3].rotate_right(10) ^ self.q[i1023].rotate_right(23))
.wrapping_add(self.p[(self.q[i3] ^ self.q[i1023]) as usize & 0x3ff]);
h(&self.p, self.q[i12]) ^ self.q[i]
};
self.c = (self.c + 1) & 0x7ff;
output
}
}
#[inline]
fn h(q: &[u32], u: u32) -> u32 {
q[(u & 0xff) as usize]
.wrapping_add(q[256 + (u >> 8 & 0xff) as usize])
.wrapping_add(q[512 + (u >> 16 & 0xff) as usize])
.wrapping_add(q[768 + (u >> 24 & 0xff) as usize])
}
#[inline]
fn f1(x: u32) -> u32 {
x.rotate_right(7)
^ x.rotate_right(18)
^ x.wrapping_shr(3)
}
#[inline]
fn f2(x: u32) -> u32 {
x.rotate_right(17)
^ x.rotate_right(19)
^ x.wrapping_shr(10)
}
#[test]
fn test() {
assert_eq!(
Hc256Rng::init(&[0; 8], &[0; 8]).gen(),
2240350043
);
}