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use gmp::mpz::Mpz;
use gmp::rand::RandState;
pub fn generate_urandom(randstate: &mut RandState, len: usize) -> Mpz {
let mut a : Mpz = randstate.urandom_2exp(len as u64 - 1);
a.setbit(len - 1);
assert!(a.bit_length() == len);
a
}
pub fn generate_prime(randstate: &mut RandState, len: usize) -> Mpz {
loop {
let a: Mpz = generate_urandom(randstate, len);
let p: Mpz = a.nextprime();
if p.bit_length() == len { return p; }
}
}
pub fn generate_strong_prime(mut randstate: &mut RandState, len: usize) -> Mpz {
let pp = generate_prime(randstate, len / 2);
let a = generate_urandom(randstate, len - len / 2 + 1);
let mut p: Mpz = &pp * &a + Mpz::one();
assert!( p.bit_length() >= len);
loop {
if p.probab_prime_p(40) {
if p.bit_length() == len {
return p;
} else {
return generate_strong_prime(&mut randstate, len);
}
}
else { p = &p + &a; }
}
}