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/* ecc-521.c.c */
/* Compile time constant (but machine dependent) tables. */
/* nettle, low-level cryptographics library
*
* Copyright (C) 2013 Niels Möller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle 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 the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02111-1301, USA.
*/
/* Development of Nettle's ECC support was funded by the .SE Internet Fund. */
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include "ecc-internal.h"
#define USE_REDC 0
#include "ecc-521.h"
#if HAVE_NATIVE_ecc_521_modp
#define ecc_521_modp nettle_ecc_521_modp
void
ecc_521_modp (const struct ecc_curve *ecc, mp_limb_t *rp);
#else
#define B_SHIFT (521 % GMP_NUMB_BITS)
#define BMODP_SHIFT (GMP_NUMB_BITS - B_SHIFT)
#define BMODP ((mp_limb_t) 1 << BMODP_SHIFT)
/* Result may be *slightly* larger than 2^521 */
static void
ecc_521_modp (const struct ecc_curve *ecc UNUSED, mp_limb_t *rp)
{
/* FIXME: Should use mpn_addlsh_n_ip1 */
mp_limb_t hi;
/* Reduce from 2*ECC_LIMB_SIZE to ECC_LIMB_SIZE + 1 */
rp[ECC_LIMB_SIZE]
= mpn_addmul_1 (rp, rp + ECC_LIMB_SIZE, ECC_LIMB_SIZE, BMODP);
hi = mpn_addmul_1 (rp, rp + ECC_LIMB_SIZE, 1, BMODP);
hi = sec_add_1 (rp + 1, rp + 1, ECC_LIMB_SIZE - 1, hi);
/* Combine hi with top bits, and add in. */
hi = (hi << BMODP_SHIFT) | (rp[ECC_LIMB_SIZE-1] >> B_SHIFT);
rp[ECC_LIMB_SIZE-1] = (rp[ECC_LIMB_SIZE-1]
& (((mp_limb_t) 1 << B_SHIFT)-1))
+ sec_add_1 (rp, rp, ECC_LIMB_SIZE - 1, hi);
}
#endif
const struct ecc_curve nettle_secp_521r1 =
{
521,
ECC_LIMB_SIZE,
ECC_BMODP_SIZE,
ECC_BMODQ_SIZE,
USE_REDC,
ECC_REDC_SIZE,
ECC_PIPPENGER_K,
ECC_PIPPENGER_C,
ecc_p,
ecc_b,
ecc_q,
ecc_g,
ecc_redc_g,
ecc_521_modp,
ecc_generic_redc,
ecc_521_modp,
ecc_generic_modq,
ecc_Bmodp,
ecc_Bmodp_shifted,
ecc_pp1h,
ecc_redc_ppm1,
ecc_unit,
ecc_Bmodq,
ecc_Bmodq_shifted,
ecc_qp1h,
ecc_table
};
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