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use gmp::mpz::Mpz;
use gmp::rand::RandState;
use rand::Rng;
use rand;
use rng::generate_strong_prime;
pub struct PaiSk {
pub lambda : Mpz,
pub mu : Mpz,
}
pub struct PaiPk {
pub n : Mpz,
pub n2 : Mpz,
pub g : Mpz,
}
pub struct Paillier {
pub pk : PaiPk,
pub sk : PaiSk,
pub rs : RandState,
}
impl Paillier {
pub fn new(keysize: usize) -> Paillier {
let mut rng = rand::thread_rng();
let mut randstate = RandState::new();
randstate.seed_ui( rng.gen::<u64>() );
let (pk, sk) = Paillier::generate_key(&mut randstate, keysize);
Paillier { pk: pk, sk: sk, rs: randstate }
}
fn generate_key(mut randstate: &mut RandState, keysize: usize) -> (PaiPk, PaiSk) {
assert!(keysize % 2 == 0);
let p = generate_strong_prime(&mut randstate, keysize/2);
let q = generate_strong_prime(&mut randstate, keysize/2);
let n = &p * &q;
let g = &n + Mpz::one();
let lambda = (&p - Mpz::one()) * (&q - Mpz::one());
let mu = lambda.invert(&n).unwrap();
let n2 = &n * &n;
(PaiPk {n: n, n2: n2, g: g}, PaiSk {lambda: lambda, mu: mu} )
}
pub fn encrypt(&mut self, m: &Mpz) -> Mpz {
let mut r = self.rs.urandom(&self.pk.n);
while r.gcd(&self.pk.n) != Mpz::one() {
r = self.rs.urandom(&self.pk.n);
}
let rn = r.powm(&self.pk.n, &self.pk.n2);
let gm = m * &self.pk.n + Mpz::one();
(&gm*&rn ) % &self.pk.n2
}
pub fn decrypt(&mut self, c: &Mpz) -> Mpz {
let cl = c.powm(&self.sk.lambda, &self.pk.n2);
let lc = (cl - Mpz::one()) / &self.pk.n;
(&lc * &self.sk.mu) % &self.pk.n
}
pub fn add_cipher(&self, c1: &Mpz, c2: &Mpz) -> Mpz {
(c1 * c2) % &self.pk.n2
}
pub fn add_const(&self, c: &Mpz, m: &Mpz) -> Mpz {
self.add_cipher(c, &self.pk.g.powm(&m, &self.pk.n2))
}
pub fn mul_const(&self, c: &Mpz, m: &Mpz) -> Mpz {
c.powm(&m, &self.pk.n2)
}
}