ltc_ecc_map.c

00001 /*
00002 MiniTLS - A super trimmed down TLS/SSL Library for embedded devices
00003 Author: Donatien Garnier
00004 Copyright (C) 2013-2014 AppNearMe Ltd
00005 
00006 This program is free software; you can redistribute it and/or
00007 modify it under the terms of the GNU General Public License
00008 as published by the Free Software Foundation; either version 2
00009 of the License, or (at your option) any later version.
00010 
00011 This program is distributed in the hope that it will be useful,
00012 but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 GNU General Public License for more details.
00015 
00016 You should have received a copy of the GNU General Public License
00017 along with this program; if not, write to the Free Software
00018 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
00019 *//* LibTomCrypt, modular cryptographic library -- Tom St Denis
00020  *
00021  * LibTomCrypt is a library that provides various cryptographic
00022  * algorithms in a highly modular and flexible manner.
00023  *
00024  * The library is free for all purposes without any express
00025  * guarantee it works.
00026  *
00027  * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
00028  */
00029 
00030 /* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
00031  *
00032  * All curves taken from NIST recommendation paper of July 1999
00033  * Available at http://csrc.nist.gov/cryptval/dss.htm
00034  */
00035 #include "ltc.h"
00036 
00037 /**
00038   @file ltc_ecc_map.c
00039   ECC Crypto, Tom St Denis
00040 */  
00041 
00042 #ifdef LTC_MECC
00043 
00044 /**
00045   Map a projective jacbobian point back to affine space
00046   @param P        [in/out] The point to map
00047   @param modulus  The modulus of the field the ECC curve is in
00048   @param mp       The "b" value from montgomery_setup()
00049   @return MINITLS_OK on success
00050 */
00051 int ltc_ecc_map(ecc_point *P, void *modulus, void *mp)
00052 {
00053    fp_int t1, t2;
00054    int   err;
00055 
00056    LTC_ARGCHK(P       != NULL);
00057    LTC_ARGCHK(modulus != NULL);
00058    LTC_ARGCHK(mp      != NULL);
00059 
00060    if ((err = mp_init_multi(&t1, &t2, NULL)) != MINITLS_OK) {
00061       return MINITLS_ERR_MEMORY;
00062    }
00063 
00064    /* first map z back to normal */
00065    /*if ((err = */mp_montgomery_reduce(&P->z, modulus, mp);/*) != MINITLS_OK)           { goto done; }*/
00066 
00067    /* get 1/z */
00068    if ((err = mp_invmod(&P->z, modulus, &t1)) != MINITLS_OK)                      { goto done; }
00069  
00070    /* get 1/z^2 and 1/z^3 */
00071    /*if ((err = */mp_sqr(&t1, &t2);/*) != MINITLS_OK)                                    { goto done; }*/
00072    if ((err = mp_mod(&t2, modulus, &t2)) != MINITLS_OK)                           { goto done; }
00073    /*if ((err =*/ mp_mul(&t1, &t2, &t1);/*) != MINITLS_OK)                                { goto done; }*/
00074    /*if ((err =*/ mp_mod(&t1, modulus, &t1);/*) != MINITLS_OK)                           { goto done; }*/
00075 
00076    /* multiply against x/y */
00077    /*if ((err =*/ mp_mul(&P->x, &t2, &P->x);/*) != MINITLS_OK)                            { goto done; }*/
00078    /*if ((err =*/ mp_montgomery_reduce(&P->x, modulus, mp);/*) != MINITLS_OK)           { goto done; }*/
00079    /*if ((err =*/ mp_mul(&P->y, &t1, &P->y);/*) != MINITLS_OK)                            { goto done; }*/
00080    /*if ((err =*/ mp_montgomery_reduce(&P->y, modulus, mp);/*) != MINITLS_OK)           { goto done; }*/
00081    /*if ((err =*/ mp_set(&P->z, 1);/*) != MINITLS_OK)                                   { goto done; }*/
00082 
00083    err = MINITLS_OK;
00084 done:
00085    mp_clear_multi(&t1, &t2, NULL);
00086    return err;
00087 }
00088 
00089 #endif
00090 
00091 /* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ltc_ecc_map.c,v $ */
00092 /* $Revision: 1.7 $ */
00093 /* $Date: 2007/05/12 14:32:35 $ */
00094