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use crate::jubjub::{edwards, JubjubEngine, PrimeOrder};
use fff::PrimeField;
use crate::constants;
use blake2s_simd::Params;
pub fn group_hash<E: JubjubEngine>(
tag: &[u8],
personalization: &[u8],
params: &E::Params,
) -> Option<edwards::Point<E, PrimeOrder>> {
assert_eq!(personalization.len(), 8);
assert!(E::Fr::NUM_BITS == 255);
let mut p = Params::new();
p.hash_length(32);
p.personal(personalization);
p.key(&[]);
p.salt(&[]);
let mut h = p.to_state();
h.update(constants::GH_FIRST_BLOCK);
h.update(tag);
let h = h.finalize().as_ref().to_vec();
assert!(h.len() == 32);
match edwards::Point::<E, _>::read(&h[..], params) {
Ok(p) => {
let p = p.mul_by_cofactor(params);
if p != edwards::Point::zero() {
Some(p)
} else {
None
}
}
Err(_) => None,
}
}