56 lines
1.7 KiB
C
56 lines
1.7 KiB
C
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/*
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* cifra - embedded cryptography library
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* Written in 2014 by Joseph Birr-Pixton <jpixton@gmail.com>
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*
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* To the extent possible under law, the author(s) have dedicated all
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* copyright and related and neighboring rights to this software to the
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* public domain worldwide. This software is distributed without any
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* warranty.
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*
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* You should have received a copy of the CC0 Public Domain Dedication
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* along with this software. If not, see
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* <http://creativecommons.org/publicdomain/zero/1.0/>.
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*/
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#ifndef GF128_H
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#define GF128_H
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#include <stddef.h>
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#include <stdint.h>
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/**
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* @brief Operations in GF(2^128).
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*
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* These implementations are constant time, but relatively slow.
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*/
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typedef uint32_t cf_gf128[4];
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/* Unpack from big-endian bytes into out. */
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void cf_gf128_frombytes_be(const uint8_t in[16], cf_gf128 out);
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/* Pack in big-endian order into out. */
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void cf_gf128_tobytes_be(const cf_gf128 in, uint8_t out[16]);
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/* out = 2 * in. Arguments may not alias. */
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void cf_gf128_double(const cf_gf128 in, cf_gf128 out);
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/* out = 2 * in. Arguments may not alias.
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* This differs from cf_gf128_double because it interprets the
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* block in little endian: the lsb is the msb of the
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* first element, the msb is the lsb of the last element.
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*
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* GCM uses this convention. */
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void cf_gf128_double_le(const cf_gf128 in, cf_gf128 out);
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/* out = x + y. Arguments may alias. */
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void cf_gf128_add(const cf_gf128 x, const cf_gf128 y, cf_gf128 out);
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/* out = xy. Arguments may alias.
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*
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* This uses cf_gf128_double_le internally, and is suitable for
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* GCM. */
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void cf_gf128_mul(const cf_gf128 x, const cf_gf128 y, cf_gf128 out);
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#endif
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