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/* nettle, low-level cryptographics library
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* Copyright (C) 2013 Niels Möller
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* The nettle library is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or (at your
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* option) any later version.
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* The nettle library is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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* License for more details.
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* You should have received a copy of the GNU Lesser General Public License
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* along with the nettle library; see the file COPYING.LIB. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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/* Development of Nettle's ECC support was funded by the .SE Internet Fund. */
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#include "ecc-internal.h"
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/* Convert hash value to an integer. If the digest is larger than
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the ecc bit size, then we must truncate it and use the leftmost
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/* NOTE: We don't considered the hash value to be secret, so it's ok
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if the running time of this conversion depends on h.
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Requires ecc->size + 1 limbs, the extra limb may be needed for
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ecc_hash (const struct ecc_curve *ecc,
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unsigned length, const uint8_t *digest)
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if (length > ((unsigned) ecc->bit_size + 7) / 8)
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length = (ecc->bit_size + 7) / 8;
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mpn_set_base256 (hp, ecc->size + 1, digest, length);
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if (8 * length > ecc->bit_size)
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/* We got a few extra bits, at the low end. Discard them. */
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mpn_rshift (hp, hp, ecc->size + 1, 8*length - ecc->bit_size);