use polymul_fast

Use polymul_fast function from ring_lwe for dot product and matrix multiplication.  Also, decrypt function updated to use paramters as input.

Author: tjaysilver

Cargo.toml

@@ -13,4 +13,5 @@ polynomial-ring = "0.5.0"
 num-traits = "=0.2.19"
 rand = "0.8.5"
 rand_distr = "0.4.3"
+ntt = "0.1.9"
 ring-lwe = "0.1.5"

src/decrypt.rs

@@ -18,17 +18,17 @@ use crate::utils::{Parameters,mul_vec_simple};
 /// let mut m_b = vec![0,1,0,1,0,0,1,1,1,0,1];
 /// m_b.resize(params.n, 0);
 /// let (u, v) = module_lwe::encrypt::encrypt(&pk.0, &pk.1, &m_b, &params, None);
-/// let decrypted_coeffs = module_lwe::decrypt::decrypt(&sk, params.q, &params.f, &u, &v);
+/// let decrypted_coeffs = module_lwe::decrypt::decrypt(&sk, &u, &v, &params);
 /// assert_eq!(m_b, decrypted_coeffs);
 /// ```
 pub fn decrypt(
     sk: &Vec<Polynomial<i64>>,    //secret key
-    q: i64,                     //ciphertext modulus
-    f: &Polynomial<i64>,  //polynomial modulus
     u: &Vec<Polynomial<i64>>, //ciphertext vector
-	v: &Polynomial<i64> 		//ciphertext polynomial
+	v: &Polynomial<i64> ,		//ciphertext polynomial
+    params: &Parameters
 ) -> Vec<i64> {
-	let scaled_pt = polysub(&v, &mul_vec_simple(&sk, &u, q, &f), q, f); //Compute v-sk*u mod q
+	let (q, f, omega) = (params.q, &params.f, params.omega); //get parameters
+	let scaled_pt = polysub(&v, &mul_vec_simple(&sk, &u, q, &f, omega), q, f); //Compute v-sk*u mod q
 	let half_q = nearest_int(q,2); // compute nearest integer to q/2
 	let mut decrypted_coeffs = vec![];
 	let mut s;
@@ -49,7 +49,7 @@ pub fn decrypt(
 pub fn decrypt_string(sk_string: &String, ciphertext_string: &String, params: &Parameters) -> String {
 
     //get parameters
-    let (n, q, k, f) = (params.n, params.q, params.k, &params.f);
+    let (n, k) = (params.n, params.k);
 
     // Convert the secret key string into a Vec<Polynomial<i64>>
     let sk_array: Vec<i64> = sk_string.split(',')
@@ -79,7 +79,7 @@ pub fn decrypt_string(sk_string: &String, ciphertext_string: &String, params: &P
         let v = Polynomial::new(v_array.to_vec());
 
         // Decrypt the ciphertext
-        let mut m_b = decrypt(&sk, q, &f, &u, &v);
+        let mut m_b = decrypt(&sk, &u, &v, &params);
         m_b.resize(n,0);
 
         message_binary.extend(m_b);

src/encrypt.rs

@@ -27,7 +27,7 @@ pub fn encrypt(
 ) -> (Vec<Polynomial<i64>>, Polynomial<i64>) {
 
     //get parameters
-    let (n, q, k, f) = (params.n, params.q, params.k, &params.f);
+    let (n, q, k, f, omega) = (params.n, params.q, params.k, &params.f, params.omega);
 
     //generate random ephermal keys
     let r = gen_small_vector(n, k, seed);
@@ -41,10 +41,10 @@ pub fn encrypt(
     let m = Polynomial::new(vec![half_q])*Polynomial::new(m_b.to_vec());
 
     // Compute u = a^T * r + e_1 mod q
-    let u = add_vec(&mul_mat_vec_simple(&transpose(a), &r, q, f), &e1, q, f);
+    let u = add_vec(&mul_mat_vec_simple(&transpose(a), &r, q, f, omega), &e1, q, f);
 
     // Compute v = t * r + e_2 - m mod q
-    let v = polysub(&polyadd(&mul_vec_simple(t, &r, q, &f), &e2, q, f), &m, q, f);
+    let v = polysub(&polyadd(&mul_vec_simple(t, &r, q, &f, omega), &e2, q, f), &m, q, f);
 
     (u, v)
 }

src/keygen.rs

@@ -17,12 +17,12 @@ pub fn keygen(
 	params: &Parameters,
     seed: Option<u64> //random seed
 ) -> ((Vec<Vec<Polynomial<i64>>>, Vec<Polynomial<i64>>), Vec<Polynomial<i64>>) {
-    let (n,q,k,f) = (params.n, params.q, params.k, &params.f);
+    let (n,q,k,f,omega) = (params.n, params.q, params.k, &params.f, params.omega);
     //Generate a public and secret key
     let a = gen_uniform_matrix(n, k, q, seed);
     let sk = gen_small_vector(n, k, seed);
     let e = gen_small_vector(n, k, seed);
-    let t = add_vec(&mul_mat_vec_simple(&a, &sk, q, &f), &e, q, &f);
+    let t = add_vec(&mul_mat_vec_simple(&a, &sk, q, &f, omega), &e, q, &f);
 
     //Return public key (a, t) and secret key (sk) as a 2-tuple
     ((a, t), sk)

src/test.rs

@@ -49,7 +49,7 @@ mod tests {
         let ciphertext_sum = (add_vec(&u.0,&v.0,q,f), polyadd(&u.1,&v.1,q,f));
 
         // Decrypt ciphertext sum u+v
-        let mut decrypted_sum = decrypt(&sk, q, f, &ciphertext_sum.0, &ciphertext_sum.1);
+        let mut decrypted_sum = decrypt(&sk, &ciphertext_sum.0, &ciphertext_sum.1, &params);
         decrypted_sum.resize(n, 0);
 
         assert_eq!(decrypted_sum, plaintext_sum, "test failed: {:?} != {:?}", decrypted_sum, plaintext_sum);

src/utils.rs

@@ -2,7 +2,8 @@ use polynomial_ring::Polynomial;
 use rand_distr::{Uniform, Distribution};
 use rand::SeedableRng;
 use rand::rngs::StdRng;
-use ring_lwe::utils::{polyadd, polymul, gen_uniform_poly};
+use ring_lwe::utils::{polyadd, polymul_fast, gen_uniform_poly};
+use ntt::omega;
 
 #[derive(Debug)]
 /// default parameters for module-LWE
@@ -11,23 +12,26 @@ pub struct Parameters {
     pub n: usize,
 	/// Ciphertext modulus
     pub q: i64,
-	/// Plaintext modulus    
-    pub k: usize,     
+	/// Module rank	
+    pub k: usize,
+	/// 2n-th root of unity	
+    pub omega: i64,
 	/// Polynomial modulus
-    pub f: Polynomial<i64>, 
+    pub f: Polynomial<i64>,
 }
 
 /// default parameters for module-LWE
 impl Default for Parameters {
     fn default() -> Self {
         let n = 32;
-        let q = 59049;
+        let q = 12289;
         let k = 8;
+		let omega = omega(q, 2*n);
         let mut poly_vec = vec![0i64;n+1];
         poly_vec[0] = 1;
         poly_vec[n] = 1;
         let f = Polynomial::new(poly_vec);
-        Parameters { n, q, k, f }
+        Parameters { n, q, k, omega, f }
     }
 }
 
@@ -54,13 +58,14 @@ pub fn add_vec(v0: &Vec<Polynomial<i64>>, v1: &Vec<Polynomial<i64>>, modulus: i6
 /// * `v1` - vector of polynomials
 /// * `modulus` - modulus
 /// * `poly_mod` - polynomial modulus
+/// * `omega` - 2nth root of unity
 /// # Returns
 /// * `result` - polynomial
-pub fn mul_vec_simple(v0: &Vec<Polynomial<i64>>, v1: &Vec<Polynomial<i64>>, modulus: i64, poly_mod: &Polynomial<i64>) -> Polynomial<i64> {
+pub fn mul_vec_simple(v0: &Vec<Polynomial<i64>>, v1: &Vec<Polynomial<i64>>, modulus: i64, poly_mod: &Polynomial<i64>, omega: i64) -> Polynomial<i64> {
 	assert!(v0.len() == v1.len());
 	let mut result = Polynomial::new(vec![]);
 	for i in 0..v0.len() {
-		result = polyadd(&result, &polymul(&v0[i], &v1[i], modulus, &poly_mod), modulus, &poly_mod);
+		result = polyadd(&result, &polymul_fast(&v0[i], &v1[i], modulus, &poly_mod, omega), modulus, &poly_mod);
 	}
 	result
 }
@@ -71,13 +76,14 @@ pub fn mul_vec_simple(v0: &Vec<Polynomial<i64>>, v1: &Vec<Polynomial<i64>>, modu
 /// * `v` - vector of polynomials
 /// * `modulus` - modulus
 /// * `poly_mod` - polynomial modulus
+/// * `omega` - 2nth root of unity
 /// # Returns
 /// * `result` - vector of polynomials
-pub fn mul_mat_vec_simple(m: &Vec<Vec<Polynomial<i64>>>, v: &Vec<Polynomial<i64>>, modulus: i64, poly_mod: &Polynomial<i64>) -> Vec<Polynomial<i64>> {
+pub fn mul_mat_vec_simple(m: &Vec<Vec<Polynomial<i64>>>, v: &Vec<Polynomial<i64>>, modulus: i64, poly_mod: &Polynomial<i64>, omega: i64) -> Vec<Polynomial<i64>> {
 
 	let mut result = vec![];
 	for i in 0..m.len() {
-		result.push(mul_vec_simple(&m[i], &v, modulus, &poly_mod));
+		result.push(mul_vec_simple(&m[i], &v, modulus, &poly_mod, omega));
 	}
 	result
 }