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#![cfg_attr(not(feature = "std"), no_std)]
use sha3::{Digest, Keccak256};
use rand_chacha::ChaCha20Rng;
use rand_core::{RngCore, SeedableRng};
pub const PERSONALIZATION: &'static [u8; 8] = b"__fawkes";
fn keccak256(data:&[u8])->[u8;32] {
let mut hasher = Keccak256::new();
hasher.update(data);
let mut res = [0u8;32];
res.iter_mut().zip(hasher.finalize().into_iter()).for_each(|(l,r)| *l=r);
res
}
pub struct SeedboxChaCha20(ChaCha20Rng);
pub trait SeedBox {
fn fill_bytes(&mut self, dest: &mut [u8]);
fn fill_limbs(&mut self, dest: &mut [u64]);
fn new_with_salt(salt: &[u8]) -> Self;
}
impl SeedBox for SeedboxChaCha20 {
fn new_with_salt(salt: &[u8]) -> Self {
SeedboxChaCha20(<ChaCha20Rng as SeedableRng>::from_seed(keccak256(salt)))
}
fn fill_bytes(&mut self, dest: &mut [u8]) {
self.0.fill_bytes(dest);
}
fn fill_limbs(&mut self, dest: &mut [u64]) {
dest.iter_mut().for_each(|f| *f = self.0.next_u64());
}
}
pub trait SeedBoxGen<Out>: SeedBox {
fn gen(&mut self) -> Out;
}
pub trait FromSeed<S:SeedBoxGen<Self>> : Sized {
fn from_seed(seed: &[u8]) -> Self;
}
impl<Out, S> FromSeed<S> for Out where S:SeedBoxGen<Out> {
fn from_seed(seed: &[u8]) -> Self {
let mut sb = S::new_with_salt(seed);
sb.gen()
}
}