Implement ring multiplication method

src/libstrongswan/plugins/ntru/ntru_crypto/ntru_crypto_ntru_encrypt.c

@@ -111,7 +111,6 @@ ntru_crypto_ntru_encrypt(
 	uint8_t                *mask_trits;
 	chunk_t                 seed;
 	ntru_poly_t				*r_poly;
-	uint16_t				*r_indices;
 
     /* check for bad parameters */
 
@@ -230,8 +229,8 @@ ntru_crypto_ntru_encrypt(
 
 			seed = chunk_create(tmp_buf, ptr - tmp_buf);
 			r_poly = ntru_poly_create(hash_algid, seed, params->c_bits,
-									  params->N, 2 * params->dF_r,
+									  params->N, params->q, params->dF_r,
-									  params->is_product_form);
+									  params->dF_r, params->is_product_form);
 			if (!r_poly)
 			{
 			   result = NTRU_MGF1_FAIL;
@@ -249,21 +248,7 @@ ntru_crypto_ntru_encrypt(
 								   params->q_bits, ringel_buf);
 
 			/* form R = h * r */
-			r_indices = r_poly->get_indices(r_poly);
+			r_poly->ring_mult(r_poly, ringel_buf, ringel_buf);
-
-			if (params->is_product_form)
-			{
-				ntru_ring_mult_product_indices(ringel_buf, (uint16_t)dr1,
-											   (uint16_t)dr2, (uint16_t)dr3,
-											   r_indices, params->N, params->q,
-											   scratch_buf, ringel_buf);
-			}
-			else
-			{
-				ntru_ring_mult_indices(ringel_buf, (uint16_t)dr, (uint16_t)dr,
-									   r_indices, params->N, params->q,
-									   scratch_buf, ringel_buf);
-			}
 			r_poly->destroy(r_poly);
 
 			/* form R mod 4 */
@@ -459,7 +444,6 @@ ntru_crypto_ntru_decrypt(
 	uint8_t                *mask_trits;
 	chunk_t                 seed;
 	ntru_poly_t			   *r_poly;
-	uint16_t			   *r_indices;
 
 	/* check for bad parameters */
 	if (!privkey_blob || !ct || !pt_len)
@@ -582,29 +566,41 @@ ntru_crypto_ntru_decrypt(
                                        (uint16_t)dF_r2, (uint16_t)dF_r3,
                                        i_buf, params->N, params->q,
                                        scratch_buf, ringel_buf1);
-        for (i = 0; i < cmprime_len; i++) {
+
-            ringel_buf1[i] = (ringel_buf2[i] + 3 * ringel_buf1[i]) & mod_q_mask;
+		for (i = 0; i < cmprime_len; i++)
-            if (ringel_buf1[i] >= (params->q >> 1))
+		{
-                    ringel_buf1[i] = ringel_buf1[i] - q_mod_p;
+			ringel_buf1[i] = (ringel_buf2[i] + 3 * ringel_buf1[i]) & mod_q_mask;
-            Mtrin_buf[i] = (uint8_t)(ringel_buf1[i] % 3);
+			if (ringel_buf1[i] >= (params->q >> 1))
-            if (Mtrin_buf[i] == 1)
+			{
-                ++m1;
+				ringel_buf1[i] = ringel_buf1[i] - q_mod_p;
-            else if (Mtrin_buf[i] == 2)
+			}
-                --m1;
+			Mtrin_buf[i] = (uint8_t)(ringel_buf1[i] % 3);
-        }
+			if (Mtrin_buf[i] == 1)
-    }
+			{
+				++m1;
+			}
+			else if (Mtrin_buf[i] == 2)
+			{
+				--m1;
+			}
+		}
+	}
 	else
 	{
         ntru_ring_mult_indices(ringel_buf2, (uint16_t)dF_r, (uint16_t)dF_r,
                                i_buf, params->N, params->q,
                                scratch_buf, ringel_buf1);
-        for (i = 0; i < cmprime_len; i++) {
+
-            ringel_buf1[i] = (ringel_buf2[i] + 3 * ringel_buf1[i]) & mod_q_mask;
+		for (i = 0; i < cmprime_len; i++)
-            if (ringel_buf1[i] >= (params->q >> 1))
+		{
-                    ringel_buf1[i] = ringel_buf1[i] - q_mod_p;
+			ringel_buf1[i] = (ringel_buf2[i] + 3 * ringel_buf1[i]) & mod_q_mask;
-            Mtrin_buf[i] = (uint8_t)(ringel_buf1[i] % 3);
+			if (ringel_buf1[i] >= (params->q >> 1))
-        }
+			{
-    }
+				ringel_buf1[i] = ringel_buf1[i] - q_mod_p;
+			}
+			Mtrin_buf[i] = (uint8_t)(ringel_buf1[i] % 3);
+		}
+}
 
     /* check that the candidate message representative meets minimum weight
      * requirements
@@ -712,8 +708,8 @@ ntru_crypto_ntru_decrypt(
 
 		seed = chunk_create(tmp_buf, ptr - tmp_buf);
 		r_poly = ntru_poly_create(hash_algid, seed, params->c_bits,
-								  params->N, 2 * params->dF_r,
+								  params->N, params->q, params->dF_r,
-								  params->is_product_form);
+								  params->dF_r, params->is_product_form);
 		if (!r_poly)
 		{
 		   result = NTRU_MGF1_FAIL;
@@ -733,20 +729,7 @@ ntru_crypto_ntru_decrypt(
 		}
 
 		/* form cR' = h * cr */
-		r_indices = r_poly->get_indices(r_poly);
+		r_poly->ring_mult(r_poly, ringel_buf1, ringel_buf1);
-		if (params->is_product_form)
-		{
-			ntru_ring_mult_product_indices(ringel_buf1, (uint16_t)dF_r1,
-										   (uint16_t)dF_r2, (uint16_t)dF_r3,
-										   r_indices, params->N, params->q,
-										   scratch_buf, ringel_buf1);
-		}
-		else
-		{
-			ntru_ring_mult_indices(ringel_buf1, (uint16_t)dF_r, (uint16_t)dF_r,
-								   r_indices, params->N, params->q,
-								   scratch_buf, ringel_buf1);
-		}
 		r_poly->destroy(r_poly);
 
 		/* compare cR' to cR */
@@ -857,7 +840,7 @@ ntru_crypto_ntru_encrypt_keygen(
     uint32_t                result = NTRU_OK;
 	ntru_poly_t			   *F_poly = NULL;
 	ntru_poly_t            *g_poly = NULL;
-	uint16_t			   *F_indices, *g_indices;
+	uint16_t			   *F_indices;
 
     /* get a pointer to the parameter-set parameters */
 
@@ -959,8 +942,8 @@ ntru_crypto_ntru_encrypt_keygen(
 
 		seed = chunk_create(tmp_buf, seed_len);
 		F_poly = ntru_poly_create(hash_algid, seed, params->c_bits,
-								  params->N, 2 * params->dF_r,
+								  params->N, params->q, params->dF_r,
-								  params->is_product_form);
+								  params->dF_r, params->is_product_form);
 		if (!F_poly)
 		{
 		   result = NTRU_MGF1_FAIL;
@@ -1055,7 +1038,8 @@ ntru_crypto_ntru_encrypt_keygen(
 
 		seed = chunk_create(tmp_buf, seed_len);
 		g_poly = ntru_poly_create(hash_algid, seed, params->c_bits,
-								  params->N, 2*params->dg + 1, FALSE);
+								  params->N, params->q, params->dg + 1,
+								  params->dg, FALSE);
 		if (!g_poly)
 		{
 		   result = NTRU_MGF1_FAIL;
@@ -1067,10 +1051,7 @@ ntru_crypto_ntru_encrypt_keygen(
 		uint16_t i;
 
 		/* compute h = p * (f^-1 * g) mod q */
-		g_indices = g_poly->get_indices(g_poly);
+		g_poly->ring_mult(g_poly, ringel_buf2, ringel_buf2);
-		ntru_ring_mult_indices(ringel_buf2, params->dg + 1, params->dg,
-							   g_indices, params->N, params->q, scratch_buf,
-							   ringel_buf2);
 		g_poly->destroy(g_poly);
 
 		for (i = 0; i < params->N; i++)

src/libstrongswan/plugins/ntru/ntru_poly.c

@@ -22,6 +22,15 @@
 #include <utils/test.h>
 
 typedef struct private_ntru_poly_t private_ntru_poly_t;
+typedef struct indices_len_t indices_len_t;
+
+/**
+ * Stores number of +1 and -1 coefficients
+ */
+struct indices_len_t {
+	int p;
+	int m;
+};
 
 /**
  * Private data of an ntru_poly_t object.
@@ -33,22 +42,44 @@ struct private_ntru_poly_t {
 	 */
 	ntru_poly_t public;
 
+	/**
+	 * Ring dimension equal to the number of polynomial coefficients
+	 */
+	uint16_t N;
+
+	/**
+	 * Large modulus
+	 */
+	uint16_t q;
+
 	/**
 	 * Array containing the indices of the non-zero coefficients
 	 */
 	uint16_t *indices;
 
 	/**
-	 * Number of non-zero coefficients
+	 * Number of sparse polynomials
 	 */
-	uint32_t indices_len;
+	int num_polynomials;
+
+	/**
+	 * Number of nonzero coefficients for up to 3 sparse polynomials
+	 */
+	indices_len_t indices_len[3];
 
 };
 
 METHOD(ntru_poly_t, get_size, size_t,
 	private_ntru_poly_t *this)
 {
-	return this->indices_len;
+	int n;
+	size_t size = 0;
+
+	for (n = 0; n < this->num_polynomials; n++)
+	{
+		size += this->indices_len[n].p + this->indices_len[n].m;
+	}
+	return size;
 }
 
 METHOD(ntru_poly_t, get_indices, uint16_t*,
@@ -56,11 +87,113 @@ METHOD(ntru_poly_t, get_indices, uint16_t*,
 {
 	return this->indices;
 }
+/**
+  * Multiplication of polynomial a with a sparse polynomial b given by
+  * the indices of its +1 and -1 coefficients results in polynomial c.
+  * This is a convolution operation
+  */
+static void ring_mult_indices(uint16_t *a, indices_len_t len, uint16_t *indices,
+							  uint16_t N, uint16_t mod_q_mask, uint16_t *c)
+{
+	uint16_t *t;
+	int i, j, k;
+
+	/* allocate and initialize temporary array t */
+	t = malloc(N * sizeof(uint16_t));
+	for (k = 0; k < N; k++)
+	{
+		t[k] = 0;
+	}
+
+	/* t[(i+k)%N] = sum i=0 through N-1 of a[i], for b[k] = -1 */
+	for (j = len.p; j < len.p + len.m; j++)
+	{
+		k = indices[j];
+		for (i = 0; k < N; ++i, ++k)
+		{
+			t[k] += a[i];
+		}
+		for (k = 0; i < N; ++i, ++k)
+		{
+			t[k] += a[i];
+		}
+	}
+
+	/* t[(i+k)%N] = -(sum i=0 through N-1 of a[i] for b[k] = -1) */
+	for (k = 0; k < N; k++)
+	{
+		t[k] = -t[k];
+	}
+
+	/* t[(i+k)%N] += sum i=0 through N-1 of a[i] for b[k] = +1 */
+	for (j = 0; j < len.p; j++)
+	{
+		k = indices[j];
+		for (i = 0; k < N; ++i, ++k)
+		{
+			t[k] += a[i];
+		}
+		for (k = 0; i < N; ++i, ++k)
+		{
+			t[k] += a[i];
+		}
+	}
+
+	/* c = (a * b) mod q */
+	for (k = 0; k < N; k++)
+	{
+		c[k] = t[k] & mod_q_mask;
+	}
+
+	/* cleanup */
+	free(t);
+}
+
+METHOD(ntru_poly_t, ring_mult, void,
+	private_ntru_poly_t *this, uint16_t *a, uint16_t *c)
+{
+	uint16_t *bi = this->indices, mod_q_mask = this->q - 1;
+
+	if (this->num_polynomials == 1)
+	{
+		ring_mult_indices(a, this->indices_len[0], bi, this->N, mod_q_mask, c);
+	}
+	else
+	{
+		uint16_t *t1, *t2;
+		int i;
+
+		/* allocate temporary arrays */
+		t1 = malloc(this->N * sizeof(uint16_t));
+		t2 = malloc(this->N * sizeof(uint16_t));
+
+		/* t1 = a * b1 */
+		ring_mult_indices(a, this->indices_len[0], bi, this->N, mod_q_mask, t1);
+
+		/* t1 = (a * b1) * b2 */
+		bi += this->indices_len[0].p + this->indices_len[0].m;
+		ring_mult_indices(t1, this->indices_len[1], bi, this->N, mod_q_mask, t1);
+
+		/* t2 = a * b3 */
+		bi += this->indices_len[1].p + this->indices_len[1].m;
+		ring_mult_indices(a, this->indices_len[2], bi, this->N, mod_q_mask, t2);
+
+		/* c = (a * b1 * b2) + (a * b3) */
+		for (i = 0; i < this->N; i++)
+		{
+			c[i] = (t1[i] + t2[i]) & mod_q_mask;
+		}
+
+		/* cleanup */
+		free(t1);
+		free(t2);
+	}
+}
 
 METHOD(ntru_poly_t, destroy, void,
 	private_ntru_poly_t *this)
 {
-	memwipe(this->indices, this->indices_len);
+	memwipe(this->indices, get_size(this));
 	free(this->indices);
 	free(this);
 }
@@ -69,14 +202,15 @@ METHOD(ntru_poly_t, destroy, void,
  * Described in header.
  */
 ntru_poly_t *ntru_poly_create(hash_algorithm_t alg, chunk_t seed,
-							  uint8_t c_bits, uint16_t poly_len,
+							  uint8_t c_bits, uint16_t N, uint16_t q,
-							  uint32_t indices_count, bool is_product_form)
+							  uint32_t indices_len_p, uint32_t indices_len_m,
+							  bool is_product_form)
 {
 	private_ntru_poly_t *this;
-	size_t hash_len, octet_count = 0, i, num_polys, num_indices[3], indices_len;
+	size_t hash_len, octet_count = 0, i;
 	uint8_t octets[HASH_SIZE_SHA512], *used, num_left = 0, num_needed;
 	uint16_t index, limit, left = 0;
-	int poly_i = 0, index_i = 0;
+	int n, num_indices, index_i = 0;
 	ntru_mgf1_t *mgf1;
 
 	DBG2(DBG_LIB, "MGF1 is seeded with %u bytes", seed.len);
@@ -87,40 +221,47 @@ ntru_poly_t *ntru_poly_create(hash_algorithm_t alg, chunk_t seed,
 	}
 	i = hash_len = mgf1->get_hash_size(mgf1);
 
-	if (is_product_form)
-	{
-		num_polys = 3;
-		num_indices[0] = 0xff &  indices_count;
-		num_indices[1] = 0xff & (indices_count >> 8);
-		num_indices[2] = 0xff & (indices_count >> 16);
-		indices_len = num_indices[0] + num_indices[1] + num_indices[2];
-	}
-	else
-	{
-		num_polys = 1;
-		num_indices[0] = indices_count;
-		indices_len = indices_count;
-	}
-	used = malloc(poly_len);
-	limit = poly_len * ((1 << c_bits) / poly_len);
-
 	INIT(this,
 		.public = {
 			.get_size = _get_size,
 			.get_indices = _get_indices,
+			.ring_mult = _ring_mult,
 			.destroy = _destroy,
 		},
-		.indices_len = indices_len,
+		.N = N,
-		.indices = malloc(indices_len * sizeof(uint16_t)),
+		.q = q,
 	);
 
-	/* generate indices for all polynomials */
+	if (is_product_form)
-	while (poly_i < num_polys)
 	{
-		memset(used, 0, poly_len);
+		this->num_polynomials = 3;
+		for (n = 0; n < 3; n++)
+		{
+			this->indices_len[n].p = 0xff & indices_len_p;
+			this->indices_len[n].m = 0xff & indices_len_m;
+			indices_len_p >>= 8;
+			indices_len_m >>= 8;
+		}
+	}
+	else
+	{
+		this->num_polynomials = 1;
+		this->indices_len[0].p = indices_len_p;
+		this->indices_len[0].m = indices_len_m;
+	}
+	this->indices = malloc(sizeof(uint16_t) * get_size(this)),
+
+	used = malloc(N);
+	limit = N * ((1 << c_bits) / N);
+
+	/* generate indices for all polynomials */
+	for (n = 0; n < this->num_polynomials; n++)
+	{
+		memset(used, 0, N);
+		num_indices = this->indices_len[n].p + this->indices_len[n].m;
 
 		/* generate indices for a single polynomial */
-		while (num_indices[poly_i])
+		while (num_indices)
 		{
 			/* generate a random candidate index with a size of c_bits */		
 			do
@@ -167,19 +308,18 @@ ntru_poly_t *ntru_poly_create(hash_algorithm_t alg, chunk_t seed,
 			while (index >= limit);
 
 			/* form index and check if unique */
-			index %= poly_len;
+			index %= N;
 			if (!used[index])
 			{
 				used[index] = 1;
 				this->indices[index_i++] = index;
-				num_indices[poly_i]--;
+				num_indices--;
 			}
 		}
-		poly_i++;
 	}
 
 	DBG2(DBG_LIB, "MGF1 generates %u octets to derive %u indices",
-				   octet_count, this->indices_len);
+				   octet_count, get_size(this));
 	mgf1->destroy(mgf1);
 	free(used);
 

src/libstrongswan/plugins/ntru/ntru_poly.h

@@ -42,6 +42,11 @@ struct ntru_poly_t {
 	 */
 	uint16_t* (*get_indices)(ntru_poly_t *this);
 
+	/**
+	 * @return		array containing the indices of the non-zero coefficients
+	 */
+	void (*ring_mult)(ntru_poly_t *this, uint16_t *a, uint16_t *c);
+
 	/**
 	 * Destroy ntru_poly_t object
 	 */
@@ -53,14 +58,17 @@ struct ntru_poly_t {
  *
  * @param alg				hash algorithm to be used by MGF1
  * @param seed				seed used by MGF1 to generate trits from
- * @param poly_len			size of the trits polynomial
+ * @param N					ring dimension, number of polynomial coefficients
+ * @param q					large modulus
  * @param c_bits			number of bits for candidate index
- * @param indices_count		number of non-zero indices
+ * @param indices_len_p		number of indices for +1 coefficients
+ * @param indices_len_m		number of indices for -1 coefficients
  * @param is_product_form	generate multiple polynomials
  */
 ntru_poly_t *ntru_poly_create(hash_algorithm_t alg, chunk_t seed,
-							  uint8_t c_bits, uint16_t poly_len,
+							  uint8_t c_bits, uint16_t N, uint16_t q,
-							  uint32_t indices_count, bool is_product_form);
+							  uint32_t indices_len_p, uint32_t indices_len_m,
+							  bool is_product_form);
 
 #endif /** NTRU_POLY_H_ @}*/
 

src/libstrongswan/tests/suites/test_ntru.c

@@ -33,8 +33,8 @@ IMPORT_FUNCTION_FOR_TESTS(ntru, ntru_trits_create, ntru_trits_t*,
 
 IMPORT_FUNCTION_FOR_TESTS(ntru, ntru_poly_create, ntru_poly_t*,
 						  hash_algorithm_t alg, chunk_t seed, uint8_t c_bits,
-						  uint16_t poly_len, uint32_t indices_count,
+						  uint16_t N, uint16_t q, uint32_t indices_len_p,
-						  bool is_product_form)
+						  uint32_t indices_len_m, bool is_product_form)
 
 /**
  * NTRU parameter sets to test
@@ -302,10 +302,11 @@ END_TEST
 
 typedef struct {
 	uint8_t c_bits;
-	uint16_t poly_len;
+	uint16_t N;
+	uint16_t q;
 	bool is_product_form;
-	uint32_t indices_count;
 	uint32_t indices_len;
+	uint32_t indices_size;
 	uint16_t *indices;
 } poly_test_t;
 
@@ -427,10 +428,10 @@ mgf1_test_t mgf1_tests[] = {
 				0, 1, 1, 2, 0,  2, 2, 0, 0, 0,  1, 1, 0, 1, 0,  1, 1, 0, 1, 1,
 				0, 1, 2, 0, 1,  1, 0, 1, 2, 0,  0, 1, 2, 2, 0,  0, 2, 1, 2),
 		{
-			{	9, 439, TRUE, 2*(9 + (8 << 8) + (5 << 16)),
+			{	9, 439, 2048, TRUE, 9 + (8 << 8) + (5 << 16),
 				countof(indices_ees439ep1), indices_ees439ep1
 			},
-			{	11, 613, FALSE, 2*55,
+			{	11, 613, 2048, FALSE, 55,
 				countof(indices_ees613ep1), indices_ees613ep1
 			}
 		}
@@ -514,10 +515,10 @@ mgf1_test_t mgf1_tests[] = {
 				1, 0, 1, 0, 2,  2, 1, 0, 2, 2,  2, 2, 2, 1, 0,  2, 2, 2, 1, 2,
 				0, 2, 0, 0, 0,  0, 0, 1, 2, 0,  1, 0, 1),
 		{
-			{	13, 743, TRUE, 2*(11 + (11 << 8) + (15 << 16)),
+			{	13, 743, 2048, TRUE, 11 + (11 << 8) + (15 << 16),
 				countof(indices_ees743ep1), indices_ees743ep1
 			},
-			{	12, 1171, FALSE, 2*106,
+			{	12, 1171, 2048, FALSE, 106,
 				countof(indices_ees1171ep1), indices_ees1171ep1
 			}
 		}
@@ -632,19 +633,21 @@ START_TEST(test_ntru_poly)
 	seed.len = mgf1_tests[_i].seed_len;
 
 	p = &mgf1_tests[_i].poly_test[0];
-	poly = ntru_poly_create(HASH_UNKNOWN, seed, p->c_bits, p->poly_len,
+	poly = ntru_poly_create(HASH_UNKNOWN, seed, p->c_bits, p->N, p->q,
-							p->indices_count, p->is_product_form);
+							p->indices_len, p->indices_len,
+							p->is_product_form);
 	ck_assert(poly == NULL);
 
 	for (n = 0; n < 2; n++)
 	{
 		p = &mgf1_tests[_i].poly_test[n];
-		poly = ntru_poly_create(mgf1_tests[_i].alg, seed, p->c_bits, p->poly_len,
+		poly = ntru_poly_create(mgf1_tests[_i].alg, seed, p->c_bits, p->N, p->q,
-								p->indices_count, p->is_product_form);
+								p->indices_len, p->indices_len,
-		ck_assert(poly != NULL && poly->get_size(poly) == p->indices_len);
+								p->is_product_form);
+		ck_assert(poly != NULL && poly->get_size(poly) == p->indices_size);
 
 		indices = poly->get_indices(poly);
-		for (j = 0; j < p->indices_len; j++)
+		for (j = 0; j < p->indices_size; j++)
 		{
 			ck_assert(indices[j] == p->indices[j]);
 		}