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/*
* Off-the-Record Messaging library
* Copyright (C) 2004-2012 Ian Goldberg, Chris Alexander, Willy Lew,
* Nikita Borisov
* <otr@cypherpunks.ca>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of version 2.1 of the GNU Lesser General
* Public License as published by the Free Software Foundation.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef __DH_H__
#define __DH_H__
#define DH1536_GROUP_ID 5
typedef struct {
unsigned int groupid;
gcry_mpi_t priv, pub;
} DH_keypair;
/* Which half of the secure session id should be shown in bold? */
typedef enum {
OTRL_SESSIONID_FIRST_HALF_BOLD,
OTRL_SESSIONID_SECOND_HALF_BOLD
} OtrlSessionIdHalf;
#define OTRL_EXTRAKEY_BYTES 32
typedef struct {
unsigned char sendctr[16];
unsigned char rcvctr[16];
gcry_cipher_hd_t sendenc;
gcry_cipher_hd_t rcvenc;
gcry_md_hd_t sendmac;
unsigned char sendmackey[20];
int sendmacused;
gcry_md_hd_t rcvmac;
unsigned char rcvmackey[20];
int rcvmacused;
unsigned char extrakey[OTRL_EXTRAKEY_BYTES];
} DH_sesskeys;
/*
* Call this once, at plugin load time. It sets up the modulus and
* generator MPIs.
*/
void otrl_dh_init(void);
/*
* Initialize the fields of a DH keypair.
*/
void otrl_dh_keypair_init(DH_keypair *kp);
/*
* Copy a DH_keypair.
*/
void otrl_dh_keypair_copy(DH_keypair *dst, const DH_keypair *src);
/*
* Deallocate the contents of a DH_keypair (but not the DH_keypair
* itself)
*/
void otrl_dh_keypair_free(DH_keypair *kp);
/*
* Generate a DH keypair for a specified group.
*/
gcry_error_t otrl_dh_gen_keypair(unsigned int groupid, DH_keypair *kp);
/*
* Construct session keys from a DH keypair and someone else's public
* key.
*/
gcry_error_t otrl_dh_session(DH_sesskeys *sess, const DH_keypair *kp,
gcry_mpi_t y);
/*
* Compute the secure session id, two encryption keys, and four MAC keys
* given our DH key and their DH public key.
*/
gcry_error_t otrl_dh_compute_v2_auth_keys(const DH_keypair *our_dh,
gcry_mpi_t their_pub, unsigned char *sessionid, size_t *sessionidlenp,
gcry_cipher_hd_t *enc_c, gcry_cipher_hd_t *enc_cp,
gcry_md_hd_t *mac_m1, gcry_md_hd_t *mac_m1p,
gcry_md_hd_t *mac_m2, gcry_md_hd_t *mac_m2p);
/*
* Compute the secure session id, given our DH key and their DH public
* key.
*/
gcry_error_t otrl_dh_compute_v1_session_id(const DH_keypair *our_dh,
gcry_mpi_t their_pub, unsigned char *sessionid, size_t *sessionidlenp,
OtrlSessionIdHalf *halfp);
/*
* Deallocate the contents of a DH_sesskeys (but not the DH_sesskeys
* itself)
*/
void otrl_dh_session_free(DH_sesskeys *sess);
/*
* Blank out the contents of a DH_sesskeys (without releasing it)
*/
void otrl_dh_session_blank(DH_sesskeys *sess);
/* Increment the top half of a counter block */
void otrl_dh_incctr(unsigned char *ctr);
/* Compare two counter values (8 bytes each). Return 0 if ctr1 == ctr2,
* < 0 if ctr1 < ctr2 (as unsigned 64-bit values), > 0 if ctr1 > ctr2. */
int otrl_dh_cmpctr(const unsigned char *ctr1, const unsigned char *ctr2);
#endif
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