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view libtomcrypt/src/pk/ecc/ltc_ecc_projective_dbl_point.c @ 994:5c5ade336926

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Prefer stronger algorithms in algorithm negotiation. Prefer diffie-hellman-group14-sha1 (2048 bit) over diffie-hellman-group1-sha1 (1024 bit). Due to meet-in-the-middle attacks the effective key length of three key 3DES is 112 bits. AES is stronger and faster then 3DES. Prefer to delay the start of compression until after authentication has completed. This avoids exposing compression code to attacks from unauthenticated users. (github pull request #9)
author Fedor Brunner <fedor.brunner@azet.sk>
date Fri, 23 Jan 2015 23:00:25 +0800
parents 0cbe8f6dbf9e
children f849a5ca2efc
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 *
 * Tom St Denis, [email protected], http://libtomcrypt.com
 */

/* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
 *
 * All curves taken from NIST recommendation paper of July 1999
 * Available at http://csrc.nist.gov/cryptval/dss.htm
 */
#include "tomcrypt.h"

/**
  @file ltc_ecc_projective_dbl_point.c
  ECC Crypto, Tom St Denis
*/  

#if defined(MECC) && (!defined(MECC_ACCEL) || defined(LTM_DESC))

/**
   Double an ECC point
   @param P   The point to double
   @param R   [out] The destination of the double
   @param modulus  The modulus of the field the ECC curve is in
   @param mp       The "b" value from montgomery_setup()
   @return CRYPT_OK on success
*/
int ltc_ecc_projective_dbl_point(ecc_point *P, ecc_point *R, void *modulus, void *mp)
{
   void *t1, *t2;
   int   err;

   LTC_ARGCHK(P       != NULL);
   LTC_ARGCHK(R       != NULL);
   LTC_ARGCHK(modulus != NULL);
   LTC_ARGCHK(mp      != NULL);

   if ((err = mp_init_multi(&t1, &t2, NULL)) != CRYPT_OK) {
      return err;
   }

   if (P != R) {
      if ((err = mp_copy(P->x, R->x)) != CRYPT_OK)                                { goto done; }
      if ((err = mp_copy(P->y, R->y)) != CRYPT_OK)                                { goto done; }
      if ((err = mp_copy(P->z, R->z)) != CRYPT_OK)                                { goto done; }
   }

   /* t1 = Z * Z */
   if ((err = mp_sqr(R->z, t1)) != CRYPT_OK)                                      { goto done; }
   if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK)                 { goto done; }
   /* Z = Y * Z */
   if ((err = mp_mul(R->z, R->y, R->z)) != CRYPT_OK)                              { goto done; }
   if ((err = mp_montgomery_reduce(R->z, modulus, mp)) != CRYPT_OK)               { goto done; }
   /* Z = 2Z */
   if ((err = mp_add(R->z, R->z, R->z)) != CRYPT_OK)                              { goto done; }
   if (mp_cmp(R->z, modulus) != LTC_MP_LT) {
      if ((err = mp_sub(R->z, modulus, R->z)) != CRYPT_OK)                        { goto done; }
   }
   
   /* T2 = X - T1 */
   if ((err = mp_sub(R->x, t1, t2)) != CRYPT_OK)                                  { goto done; }
   if (mp_cmp_d(t2, 0) == LTC_MP_LT) {
      if ((err = mp_add(t2, modulus, t2)) != CRYPT_OK)                            { goto done; }
   }
   /* T1 = X + T1 */
   if ((err = mp_add(t1, R->x, t1)) != CRYPT_OK)                                  { goto done; }
   if (mp_cmp(t1, modulus) != LTC_MP_LT) {
      if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK)                            { goto done; }
   }
   /* T2 = T1 * T2 */
   if ((err = mp_mul(t1, t2, t2)) != CRYPT_OK)                                    { goto done; }
   if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK)                 { goto done; }
   /* T1 = 2T2 */
   if ((err = mp_add(t2, t2, t1)) != CRYPT_OK)                                    { goto done; }
   if (mp_cmp(t1, modulus) != LTC_MP_LT) {
      if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK)                            { goto done; }
   }
   /* T1 = T1 + T2 */
   if ((err = mp_add(t1, t2, t1)) != CRYPT_OK)                                    { goto done; }
   if (mp_cmp(t1, modulus) != LTC_MP_LT) {
      if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK)                            { goto done; }
   }

   /* Y = 2Y */
   if ((err = mp_add(R->y, R->y, R->y)) != CRYPT_OK)                              { goto done; }
   if (mp_cmp(R->y, modulus) != LTC_MP_LT) {
      if ((err = mp_sub(R->y, modulus, R->y)) != CRYPT_OK)                        { goto done; }
   }
   /* Y = Y * Y */
   if ((err = mp_sqr(R->y, R->y)) != CRYPT_OK)                                    { goto done; }
   if ((err = mp_montgomery_reduce(R->y, modulus, mp)) != CRYPT_OK)               { goto done; }
   /* T2 = Y * Y */
   if ((err = mp_sqr(R->y, t2)) != CRYPT_OK)                                      { goto done; }
   if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK)                 { goto done; }
   /* T2 = T2/2 */
   if (mp_isodd(t2)) {
      if ((err = mp_add(t2, modulus, t2)) != CRYPT_OK)                            { goto done; }
   }
   if ((err = mp_div_2(t2, t2)) != CRYPT_OK)                                      { goto done; }
   /* Y = Y * X */
   if ((err = mp_mul(R->y, R->x, R->y)) != CRYPT_OK)                              { goto done; }
   if ((err = mp_montgomery_reduce(R->y, modulus, mp)) != CRYPT_OK)               { goto done; }

   /* X  = T1 * T1 */
   if ((err = mp_sqr(t1, R->x)) != CRYPT_OK)                                      { goto done; }
   if ((err = mp_montgomery_reduce(R->x, modulus, mp)) != CRYPT_OK)               { goto done; }
   /* X = X - Y */
   if ((err = mp_sub(R->x, R->y, R->x)) != CRYPT_OK)                              { goto done; }
   if (mp_cmp_d(R->x, 0) == LTC_MP_LT) {
      if ((err = mp_add(R->x, modulus, R->x)) != CRYPT_OK)                        { goto done; }
   }
   /* X = X - Y */
   if ((err = mp_sub(R->x, R->y, R->x)) != CRYPT_OK)                              { goto done; }
   if (mp_cmp_d(R->x, 0) == LTC_MP_LT) {
      if ((err = mp_add(R->x, modulus, R->x)) != CRYPT_OK)                        { goto done; }
   }

   /* Y = Y - X */     
   if ((err = mp_sub(R->y, R->x, R->y)) != CRYPT_OK)                              { goto done; }
   if (mp_cmp_d(R->y, 0) == LTC_MP_LT) {
      if ((err = mp_add(R->y, modulus, R->y)) != CRYPT_OK)                        { goto done; }
   }
   /* Y = Y * T1 */
   if ((err = mp_mul(R->y, t1, R->y)) != CRYPT_OK)                                { goto done; }
   if ((err = mp_montgomery_reduce(R->y, modulus, mp)) != CRYPT_OK)               { goto done; }
   /* Y = Y - T2 */
   if ((err = mp_sub(R->y, t2, R->y)) != CRYPT_OK)                                { goto done; }
   if (mp_cmp_d(R->y, 0) == LTC_MP_LT) {
      if ((err = mp_add(R->y, modulus, R->y)) != CRYPT_OK)                        { goto done; }
   }
 
   err = CRYPT_OK;
done:
   mp_clear_multi(t1, t2, NULL);
   return err;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ltc_ecc_projective_dbl_point.c,v $ */
/* $Revision: 1.8 $ */
/* $Date: 2006/12/04 05:07:59 $ */