/*
 * Copyright (C) 2013, 2014 Giorgio Vazzana
 *
 * This file is part of Seren.
 *
 * Seren is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Seren is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef DHM_H
#define DHM_H

#include <stddef.h>
#include <stdint.h>
#include <gmp.h>

#define DHM_RFC3526_MODP_2048_P                         \
"FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" \
"29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" \
"EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" \
"E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" \
"EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D" \
"C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F" \
"83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D" \
"670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B" \
"E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9" \
"DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510" \
"15728E5A 8AACAA68 FFFFFFFF FFFFFFFF"

#define DHM_RFC3526_MODP_2048_G "2"

#define DHM_RFC3526_MODP_3072_P                         \
"FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" \
"29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" \
"EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" \
"E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" \
"EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D" \
"C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F" \
"83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D" \
"670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B" \
"E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9" \
"DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510" \
"15728E5A 8AAAC42D AD33170D 04507A33 A85521AB DF1CBA64" \
"ECFB8504 58DBEF0A 8AEA7157 5D060C7D B3970F85 A6E1E4C7" \
"ABF5AE8C DB0933D7 1E8C94E0 4A25619D CEE3D226 1AD2EE6B" \
"F12FFA06 D98A0864 D8760273 3EC86A64 521F2B18 177B200C" \
"BBE11757 7A615D6C 770988C0 BAD946E2 08E24FA0 74E5AB31" \
"43DB5BFC E0FD108E 4B82D120 A93AD2CA FFFFFFFF FFFFFFFF"

#define DHM_RFC3526_MODP_3072_G "2"

#define DHM_RFC3526_MODP_4096_P                         \
"FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" \
"29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" \
"EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" \
"E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" \
"EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D" \
"C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F" \
"83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D" \
"670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B" \
"E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9" \
"DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510" \
"15728E5A 8AAAC42D AD33170D 04507A33 A85521AB DF1CBA64" \
"ECFB8504 58DBEF0A 8AEA7157 5D060C7D B3970F85 A6E1E4C7" \
"ABF5AE8C DB0933D7 1E8C94E0 4A25619D CEE3D226 1AD2EE6B" \
"F12FFA06 D98A0864 D8760273 3EC86A64 521F2B18 177B200C" \
"BBE11757 7A615D6C 770988C0 BAD946E2 08E24FA0 74E5AB31" \
"43DB5BFC E0FD108E 4B82D120 A9210801 1A723C12 A787E6D7" \
"88719A10 BDBA5B26 99C32718 6AF4E23C 1A946834 B6150BDA" \
"2583E9CA 2AD44CE8 DBBBC2DB 04DE8EF9 2E8EFC14 1FBECAA6" \
"287C5947 4E6BC05D 99B2964F A090C3A2 233BA186 515BE7ED" \
"1F612970 CEE2D7AF B81BDD76 2170481C D0069127 D5B05AA9" \
"93B4EA98 8D8FDDC1 86FFB7DC 90A6C08F 4DF435C9 34063199" \
"FFFFFFFF FFFFFFFF"

#define DHM_RFC3526_MODP_4096_G "2"

enum dhm_pgid {
	pgid_2048  = 14,
	pgid_3072  = 15,
	pgid_4096  = 16
};

#define DHM_MAX_LEN 512

struct dhm_ctx {
	enum dhm_pgid pgid; /* prime group id, from RFC 3526 */

	mpz_t         p;    /* public prime modulus */
	mpz_t         g;    /* public generator */
	mpz_t         a;    /* secret value */
	mpz_t         A;    /* public key */
	mpz_t         B;    /* peer public key */
	mpz_t         k;    /* shared secret key */

	uint8_t       pk[DHM_MAX_LEN];  /* export from A */
	size_t        pklen;

	uint8_t       sk[DHM_MAX_LEN];  /* export from k */
	size_t        sklen;

	uint8_t       key128[16]; /* 128-bit key from secret key */
	uint8_t       key256[32]; /* 256-bit key from secret key */
};

void dhm_init(struct dhm_ctx *ctx, enum dhm_pgid pgid);
void dhm_calc_secret(struct dhm_ctx *ctx, const uint8_t *peer_pk, size_t peer_pklen);
int  dhm_compare_pk(struct dhm_ctx *ctx, const uint8_t *peer_pk, size_t peer_pklen);
void dhm_clear(struct dhm_ctx *ctx);

#endif