Completed integration of ntru_crypto library into ntru plugin

2014-03-22 09:51:00 +01:00
parent b517912848
commit 22e1aa51f9
30 changed files with 1356 additions and 1712 deletions
@@ -16,10 +16,12 @@
 */

 #include "ntru_public_key.h"
-
-#include "ntru_crypto/ntru_crypto_ntru_convert.h"
+#include "ntru_trits.h"
+#include "ntru_poly.h"
+#include "ntru_convert.h"

 #include <utils/debug.h>
+#include <utils/test.h>

 typedef struct private_ntru_public_key_t private_ntru_public_key_t;

@@ -47,37 +49,268 @@ struct private_ntru_public_key_t {
 	 */
 	chunk_t encoding;

+	/**
+	 * Deterministic Random Bit Generator
+	 */
+	ntru_drbg_t *drbg;
+
 };

+METHOD(ntru_public_key_t, get_id, ntru_param_set_id_t,
+	private_ntru_public_key_t *this)
+{
+	return this->params->id;
+}
+
+/**
+ * Generate NTRU encryption public key encoding
+ */
+static void generate_encoding(private_ntru_public_key_t *this)
+{
+	size_t pubkey_len;
+	u_char *enc;
+
+	/* compute public key length encoded as packed coefficients */
+	pubkey_len =  (this->params->N * this->params->q_bits + 7) / 8;
+
+	/* allocate memory for public key encoding */
+	this->encoding = chunk_alloc(2 + NTRU_OID_LEN + pubkey_len);
+	enc = this->encoding.ptr;
+
+	/* format header and packed public key */
+	*enc++ = NTRU_PUBKEY_TAG;
+	*enc++ = NTRU_OID_LEN;
+	memcpy(enc, this->params->oid, NTRU_OID_LEN);
+	enc += NTRU_OID_LEN;
+	ntru_elements_2_octets(this->params->N, this->pubkey,
+						   this->params->q_bits, enc);
+}
+
 METHOD(ntru_public_key_t, get_encoding, chunk_t,
 	private_ntru_public_key_t *this)
 {
-	if (!this->encoding.len)
-	{
-		size_t pubkey_len;
-		u_char *enc;
-
-		/* compute public key length encoded as packed coefficients */
-		pubkey_len =  (this->params->N * this->params->q_bits + 7) / 8;
-
-		/* allocate memory for public key encoding */
-		this->encoding = chunk_alloc(2 + NTRU_OID_LEN + pubkey_len);
-		enc = this->encoding.ptr;
-
-		/* format header and packed public key */
-		*enc++ = NTRU_PUBKEY_TAG;
-		*enc++ = NTRU_OID_LEN;
-		memcpy(enc, this->params->oid, NTRU_OID_LEN);
-		enc += NTRU_OID_LEN;
-		ntru_elements_2_octets(this->params->N, this->pubkey,
-							   this->params->q_bits, enc);
-	}
 	return this->encoding;
 }

+#define MAX_SEC_STRENGTH_LEN	32 /* bytes */
+
+/**
+ * Shared with ntru_private_key.c
+ */
+extern bool ntru_check_min_weight(uint16_t N, uint8_t  *t, uint16_t min_wt);
+
+METHOD(ntru_public_key_t, encrypt, bool,
+	private_ntru_public_key_t *this, chunk_t plaintext, chunk_t *ciphertext)
+{
+	hash_algorithm_t hash_algid;
+	size_t t_len, seed1_len, seed2_len;
+	uint16_t *t1, *t = NULL;
+	uint8_t b[MAX_SEC_STRENGTH_LEN];
+	uint8_t *t2, *Mtrin, *M, *mask_trits, *ptr;
+	uint16_t mod_q_mask, mprime_len = 0;
+	int16_t m1;
+	chunk_t seed = chunk_empty;
+	ntru_trits_t *mask;
+	ntru_poly_t *r_poly;
+	bool msg_rep_good, success = FALSE;
+	int i;
+
+	*ciphertext = chunk_empty;
+
+	if (plaintext.len > this->params->m_len_max)
+	{
+		DBG1(DBG_LIB, "plaintext exceeds maximum size");
+		return FALSE;
+	}
+
+	if (this->params->sec_strength_len > MAX_SEC_STRENGTH_LEN)
+	{
+		DBG1(DBG_LIB, "required security strength exceeds %d bits",
+			 MAX_SEC_STRENGTH_LEN * BITS_PER_BYTE);
+		return FALSE;
+	}
+
+	/* allocate temporary array t */
+	t_len  = (sizeof(uint16_t) + 3*sizeof(uint8_t)) * this->params->N;
+	t = malloc(t_len);
+	t1 = t;
+	t2 = (uint8_t *)(t1 + this->params->N);
+	Mtrin = t2 + this->params->N;
+	M = Mtrin + this->params->N;
+
+	/* set hash algorithm based on security strength */
+	hash_algid = (this->params->sec_strength_len <= 20) ? HASH_SHA1 :
+														  HASH_SHA256;
+	/* set constants */
+	mod_q_mask = this->params->q - 1;
+
+	/* allocate memory for the larger of the two seeds */
+	seed1_len = (this->params->N + 3)/4;
+	seed2_len = 3 + 2*this->params->sec_strength_len + plaintext.len;
+	seed = chunk_alloc(max(seed1_len, seed2_len));
+
+	/* loop until a message representative with proper weight is achieved */
+	do
+	{
+		if (!this->drbg->generate(this->drbg,
+								  this->params->sec_strength_len * BITS_PER_BYTE,
+								  this->params->sec_strength_len, b))
+		{
+			goto err;
+		}
+
+		/* form sData (OID || m || b || hTrunc) */
+		ptr = seed.ptr;
+		memcpy(ptr, this->params->oid, NTRU_OID_LEN);
+		ptr += NTRU_OID_LEN;
+		memcpy(ptr, plaintext.ptr, plaintext.len);
+		ptr += plaintext.len;
+		memcpy(ptr, b, this->params->sec_strength_len);
+		ptr += this->params->sec_strength_len;
+		memcpy(ptr, this->encoding.ptr + 2 + NTRU_OID_LEN,
+			   this->params->sec_strength_len);
+		ptr += this->params->sec_strength_len;
+		seed.len = seed2_len;
+
+		DBG2(DBG_LIB, "generate polynomial r");
+		r_poly = ntru_poly_create_from_seed(hash_algid, seed, this->params->c_bits,
+											this->params->N, this->params->q,
+											this->params->dF_r, this->params->dF_r,
+											this->params->is_product_form);
+		if (!r_poly)
+		{
+		   goto err;
+		}
+
+		/* form R = h * r */
+		r_poly->ring_mult(r_poly, this->pubkey, t1);
+		r_poly->destroy(r_poly);
+
+		/* form R mod 4 */
+		ntru_coeffs_mod4_2_octets(this->params->N, t1, seed.ptr);
+		seed.len = seed1_len;
+
+		/* form mask */
+		mask = ntru_trits_create(this->params->N, hash_algid, seed);
+		if (!mask)
+		{
+			DBG1(DBG_LIB, "mask creation failed");
+			goto err;
+		}
+
+		/* form the padded message M */
+		ptr = M;
+		memcpy(ptr, b, this->params->sec_strength_len);
+		ptr += this->params->sec_strength_len;
+		if (this->params->m_len_len == 2)
+		{
+			*ptr++ = (uint8_t)((plaintext.len >> 8) & 0xff);
+		}
+		*ptr++ = (uint8_t)(plaintext.len & 0xff);
+		memcpy(ptr, plaintext.ptr, plaintext.len);
+		ptr += plaintext.len;
+
+		/* add an extra zero byte in case without it the bit string
+		 * is not a multiple of 3 bits and therefore might not be
+		 * able to produce enough trits
+		 */
+		memset(ptr, 0, this->params->m_len_max - plaintext.len + 2);
+
+		/* convert M to trits (Mbin to Mtrin) */
+		mprime_len = this->params->N;
+		if (this->params->is_product_form)
+		{
+			--mprime_len;
+		}
+		ntru_bits_2_trits(M, mprime_len, Mtrin);
+		mask_trits = mask->get_trits(mask);
+
+
+		/* form the msg representative m' by adding Mtrin to mask, mod p */
+		if (this->params->is_product_form)
+		{
+			m1 = 0;
+			for (i = 0; i < mprime_len; i++)
+			{
+				t2[i] = mask_trits[i] + Mtrin[i];
+				if (t2[i] >= 3)
+				{
+					t2[i] -= 3;
+				}
+				if (t2[i] == 1)
+				{
+					++m1;
+				}
+				else if (t2[i] == 2)
+				{
+					--m1;
+				}
+			}
+		}
+		else
+		{
+			for (i = 0; i < mprime_len; i++)
+			{
+				t2[i] = mask_trits[i] + Mtrin[i];
+				if (t2[i] >= 3)
+				{
+					t2[i] -= 3;
+				}
+			}
+		}
+		mask->destroy(mask);
+
+		/* check that message representative meets minimum weight
+		 * requirements
+		 */
+		if (this->params->is_product_form)
+		{
+			msg_rep_good = (abs(m1) <= this->params->min_msg_rep_wt);
+		}
+		else
+		{
+			msg_rep_good = ntru_check_min_weight(mprime_len, t2,
+												 this->params->min_msg_rep_wt);
+		}
+	}
+	while (!msg_rep_good);
+
+	/* form ciphertext e by adding m' to R mod q */
+	for (i = 0; i < mprime_len; i++)
+	{
+		if (t2[i] == 1)
+		{
+			t1[i] = (t1[i] + 1) & mod_q_mask;
+		}
+		else if (t2[i] == 2)
+		{
+			t1[i] = (t1[i] - 1) & mod_q_mask;
+		}
+	}
+	if (this->params->is_product_form)
+	{
+		t1[i] = (t1[i] - m1) & mod_q_mask;
+	}
+
+	/* pack ciphertext */
+	*ciphertext = chunk_alloc((this->params->N * this->params->q_bits + 7) / 8);
+	ntru_elements_2_octets(this->params->N, t1, this->params->q_bits,
+						   ciphertext->ptr);
+
+	memwipe(t, t_len);
+	success = TRUE;
+
+err:
+	/* cleanup */
+	chunk_clear(&seed);
+	free(t);
+
+	return success;
+}
 METHOD(ntru_public_key_t, destroy, void,
 	private_ntru_public_key_t *this)
 {
+	this->drbg->destroy(this->drbg);
 	chunk_clear(&this->encoding);
 	free(this->pubkey);
 	free(this);
@@ -86,7 +319,8 @@ METHOD(ntru_public_key_t, destroy, void,
 /*
 * Described in header.
 */
-ntru_public_key_t *ntru_public_key_create(ntru_param_set_t *params,
+ntru_public_key_t *ntru_public_key_create(ntru_drbg_t *drbg,
+										  ntru_param_set_t *params,
 										  uint16_t *pubkey)
 {
 	private_ntru_public_key_t *this;
@@ -94,11 +328,14 @@ ntru_public_key_t *ntru_public_key_create(ntru_param_set_t *params,

 	INIT(this,
 		.public = {
+			.get_id = _get_id,
 			.get_encoding = _get_encoding,
+			.encrypt = _encrypt,
 			.destroy = _destroy,
 		},
 		.params = params,
 		.pubkey = malloc(params->N * sizeof(uint16_t)),
+		.drbg = drbg->get_ref(drbg),
 	);

 	for (i = 0; i < params->N; i++)
@@ -106,5 +343,66 @@ ntru_public_key_t *ntru_public_key_create(ntru_param_set_t *params,
 		this->pubkey[i] = pubkey[i];
 	}

+	/* generate public key encoding */
+	generate_encoding(this);
+
 	return &this->public;
 }
+
+/*
+ * Described in header.
+ */
+ntru_public_key_t *ntru_public_key_create_from_data(ntru_drbg_t *drbg,
+													chunk_t data)
+{
+	private_ntru_public_key_t *this;
+	size_t header_len, pubkey_packed_len;
+	ntru_param_set_t *params;
+
+	header_len = 2 + NTRU_OID_LEN;
+
+	/* check the NTRU public key header format */
+	if (data.len < header_len ||
+		data.ptr[0] != NTRU_PUBKEY_TAG ||
+		data.ptr[1] != NTRU_OID_LEN)
+	{
+		DBG1(DBG_LIB, "received NTRU public key with invalid header");
+		return NULL;
+	}
+	params =  ntru_param_set_get_by_oid(data.ptr + 2);
+
+	if (!params)
+	{
+		DBG1(DBG_LIB, "received NTRU public key with unknown OID");
+		return NULL;
+	}
+
+	pubkey_packed_len = (params->N * params->q_bits + 7) / 8;
+
+	if (data.len < header_len + pubkey_packed_len)
+	{
+		DBG1(DBG_LIB, "received NTRU public key with wrong packed key size");
+		return NULL;
+	}
+
+	INIT(this,
+		.public = {
+			.get_id = _get_id,
+			.get_encoding = _get_encoding,
+			.encrypt = _encrypt,
+			.destroy = _destroy,
+		},
+		.params = params,
+		.pubkey = malloc(params->N * sizeof(uint16_t)),
+		.encoding = chunk_clone(data),
+		.drbg = drbg->get_ref(drbg),
+	);
+
+	/* unpack the encoded public key */
+	ntru_octets_2_elements(pubkey_packed_len, data.ptr + header_len,
+						   params->q_bits, this->pubkey);
+
+	return &this->public;
+}
+
+EXPORT_FUNCTION_FOR_TESTS(ntru, ntru_public_key_create_from_data);