Ideal Class Group Homomorphic Encryption Faster than Pailler’s

See Ideal Class Groups.

class groups have been used to construct additive homomorphic encryption that’s similar to ElGamal encryption
allows encryption of large 256-bit messages and efficient decryption by using composite order of group of unknown order with underlying subgroup of known order where the dlog is easy

Castagnos-Laguillaumie (CL) lineary homomorphic encryption scheme

M integer
setup
computations in $F$ are efficient!
exponentiations in $F$
discrete logarithm in $F$

impl<Z, BQF> ClHSMqInstance<Z, BQF>
where
    Z: crate::z::Z + Debug + Clone + std::cmp::PartialEq,
    BQF: BinaryQuadraticForm<Z> + Clone,
{
    pub fn dlog_solve_f(&self, fm: &BQF) -> Z {
        let mut m = Z::from(0u64);
        if !fm.equals(&fm.identity()) {
            m = fm.b().divide_exact(&self.q).invert_mod(&self.q).unwrap();
        }
        m
    }
}