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64 lines
1.7 KiB
C
64 lines
1.7 KiB
C
/* ecc-eh-to-a.c
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Copyright (C) 2014 Niels Möller
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This file is part of GNU Nettle.
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GNU Nettle is free software: you can redistribute it and/or
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modify it under the terms of either:
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* the GNU Lesser General Public License as published by the Free
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Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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or
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* the GNU General Public License as published by the Free
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Software Foundation; either version 2 of the License, or (at your
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option) any later version.
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or both in parallel, as here.
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GNU Nettle is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received copies of the GNU General Public License and
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the GNU Lesser General Public License along with this program. If
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not, see http://www.gnu.org/licenses/.
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*/
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#if HAVE_CONFIG_H
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# include "config.h"
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#endif
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#include <assert.h>
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#include "ecc.h"
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#include "ecc-internal.h"
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/* Convert from homogeneous coordinates on the Edwards curve to affine
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coordinates. */
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void
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ecc_eh_to_a (const struct ecc_curve *ecc,
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int op,
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mp_limb_t *r, const mp_limb_t *p,
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mp_limb_t *scratch)
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{
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#define izp scratch
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#define tp (scratch + ecc->p.size)
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#define xp p
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#define yp (p + ecc->p.size)
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#define zp (p + 2*ecc->p.size)
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assert(op == 0);
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/* Needs size + scratch for the invert call. */
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ecc->p.invert (&ecc->p, izp, zp, tp);
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ecc_mod_mul_canonical (&ecc->p, r, xp, izp, tp);
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ecc_mod_mul_canonical (&ecc->p, r + ecc->p.size, yp, izp, tp);
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}
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