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sec-add-1.c

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  • Forked from Nettle / nettle
    Source project has a limited visibility.
    ecc-mod-arith.c 4.65 KiB
    /* ecc-mod-arith.c
    
       Copyright (C) 2013, 2014 Niels Möller
    
       This file is part of GNU Nettle.
    
       GNU Nettle is free software: you can redistribute it and/or
       modify it under the terms of either:
    
         * the GNU Lesser General Public License as published by the Free
           Software Foundation; either version 3 of the License, or (at your
           option) any later version.
    
       or
    
         * the GNU General Public License as published by the Free
           Software Foundation; either version 2 of the License, or (at your
           option) any later version.
    
       or both in parallel, as here.
    
       GNU Nettle 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 copies of the GNU General Public License and
       the GNU Lesser General Public License along with this program.  If
       not, see http://www.gnu.org/licenses/.
    */
    
    /* Development of Nettle's ECC support was funded by the .SE Internet Fund. */
    
    #if HAVE_CONFIG_H
    # include "config.h"
    #endif
    
    #include <assert.h>
    
    #include "ecc-internal.h"
    
    /* Routines for modp arithmetic. All values are ecc->size limbs, but
       not necessarily < p. */
    
    void
    ecc_mod_add (const struct ecc_modulo *m, mp_limb_t *rp,
    	     const mp_limb_t *ap, const mp_limb_t *bp)
    {
      mp_limb_t cy;
      cy = mpn_add_n (rp, ap, bp, m->size);
      cy = cnd_add_n (cy, rp, m->B, m->size);
      cy = cnd_add_n (cy, rp, m->B, m->size);
      assert (cy == 0);  
    }
    
    void
    ecc_mod_sub (const struct ecc_modulo *m, mp_limb_t *rp,
    	     const mp_limb_t *ap, const mp_limb_t *bp)
    {
      mp_limb_t cy;
      cy = mpn_sub_n (rp, ap, bp, m->size);
      cy = cnd_sub_n (cy, rp, m->B, m->size);
      cy = cnd_sub_n (cy, rp, m->B, m->size);
      assert (cy == 0);  
    }
    
    void
    ecc_mod_mul_1 (const struct ecc_modulo *m, mp_limb_t *rp,
    	       const mp_limb_t *ap, mp_limb_t b)
    {
      mp_limb_t hi;
    
      assert (b <= 0xffffffff);
      hi = mpn_mul_1 (rp, ap, m->size, b);
      hi = mpn_addmul_1 (rp, m->B, m->size, hi);
      assert (hi <= 1);
      hi = cnd_add_n (hi, rp, m->B, m->size);
      /* Sufficient if b < B^size / p */
      assert (hi == 0);
    }
    
    void
    ecc_mod_addmul_1 (const struct ecc_modulo *m, mp_limb_t *rp,
    		  const mp_limb_t *ap, mp_limb_t b)
    {
      mp_limb_t hi;
    
      assert (b <= 0xffffffff);
      hi = mpn_addmul_1 (rp, ap, m->size, b);
      hi = mpn_addmul_1 (rp, m->B, m->size, hi);
      assert (hi <= 1);
      hi = cnd_add_n (hi, rp, m->B, m->size);
      /* Sufficient roughly if b < B^size / p */
      assert (hi == 0);
    }
      
    void
    ecc_mod_submul_1 (const struct ecc_modulo *m, mp_limb_t *rp,
    		  const mp_limb_t *ap, mp_limb_t b)
    {
      mp_limb_t hi;
    
      assert (b <= 0xffffffff);
      hi = mpn_submul_1 (rp, ap, m->size, b);
      hi = mpn_submul_1 (rp, m->B, m->size, hi);
      assert (hi <= 1);
      hi = cnd_sub_n (hi, rp, m->B, m->size);
      /* Sufficient roughly if b < B^size / p */
      assert (hi == 0);
    }
    
    /* NOTE: mul and sqr needs 2*m->size limbs at rp */
    void
    ecc_mod_mul (const struct ecc_modulo *m, mp_limb_t *rp,
    	     const mp_limb_t *ap, const mp_limb_t *bp)
    {
      mpn_mul_n (rp, ap, bp, m->size);
      m->reduce (m, rp);
    }
    
    void
    ecc_mod_sqr (const struct ecc_modulo *m, mp_limb_t *rp,
    	     const mp_limb_t *ap)
    {
      mpn_sqr (rp, ap, m->size);
      m->reduce (m, rp);
    }
    
    /* Computes src1 ^ ( 2 ^ scount ) * src2 */
    /* dst and scratch must both have 2*size space */
    void
    ecc_mod_pow2n_mul (const struct ecc_modulo *m,
    		   mp_limb_t * dst,
    		   const mp_limb_t * src1,
    		   const mp_limb_t * src2,
    		   mp_limb_t * scratch, unsigned scount)
    {
      ecc_mod_pow2n (m, scratch, src1, dst, scount);
      mpn_mul (dst, scratch, m->size, src2, m->size);
      m->reduce (m, dst);
    }
    
    /* computes x <- x * y; performs an extra copy since mpn_mul can't share src and dst buffers */
    void
    ecc_mod_inplc_mul (const struct ecc_modulo *m,
    		   mp_limb_t * srcdst,
    		   const mp_limb_t * src2, mp_limb_t * scratch)
    {
      mpn_mul (scratch, srcdst, m->size, src2, m->size);
      m->reduce (m, scratch);
      mpn_copyi (srcdst, scratch, m->size);
    }
    
    void
    ecc_mod_pow2n (const struct ecc_modulo *m,
    	       mp_limb_t * dst,
    	       const mp_limb_t * src, mp_limb_t * scratch, unsigned scount)
    {
      mp_size_t size = m->size;
    
      if (scount == 0)
        {
          mpn_copyi(dst, src, size);
          return;
        }
      else if (scount & 1)
        {
          mpn_sqr (dst, src, size);
          m->reduce (m, dst);
          scount -= 1;
        }
      else
        {
          mpn_sqr (scratch, src, size);
          m->reduce (m, scratch);
          mpn_sqr (dst, scratch, size);
          m->reduce (m, dst);
          scount -= 2;
        }
    
      while (scount)
        {
          mpn_sqr (scratch, dst, size);
          m->reduce (m, scratch);
          mpn_sqr (dst, scratch, size);
          m->reduce (m, dst);
          scount -= 2;
        }
    }