Function decrypt 

pub fn decrypt(
    sk: &Polynomial<i64>,
    ct: &[Polynomial<i64>; 2],
    params: &Parameters,
) -> Polynomial<i64>

Decrypt a ciphertext using the secret key

Arguments:

• sk - secret key
• ct - array of ciphertext polynomials
• params - ring-LWE parameters

Returns:

decrypted polynomial

Example:

let params = ring_lwe::utils::Parameters::default();
let (pk, sk) = ring_lwe::keygen::keygen(&params, None);
let m = polynomial_ring::Polynomial::new(vec![1, 0, 1]);
let ct = ring_lwe::encrypt::encrypt(&pk, &m, &params, None);
let decrypted_m = ring_lwe::decrypt::decrypt(&sk, &ct, &params);