Coverage Report

Created: 2024-06-28 06:39

/src/nettle-with-mini-gmp/ghash-set-key.c
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/* ghash-set-key.c
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   Galois counter mode, specified by NIST,
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   http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf
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   See also the gcm paper at
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   http://www.cryptobarn.com/papers/gcm-spec.pdf.
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   Copyright (C) 2011 Katholieke Universiteit Leuven
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   Copyright (C) 2011, 2013, 2018, 2022 Niels Möller
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   Copyright (C) 2018 Red Hat, Inc.
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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 "ghash-internal.h"
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#include "block-internal.h"
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/* For fat builds */
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#if HAVE_NATIVE_ghash_set_key
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void
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_nettle_ghash_set_key_c (struct gcm_key *ctx, const union nettle_block16 *key);
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#define _nettle_ghash_set_key _nettle_ghash_set_key_c
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#endif
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#if GCM_TABLE_BITS < 7
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# error Unsupported table size.
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#endif
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/* Implements a lookup table for processors without carryless-mul
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   instruction. */
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void
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_ghash_set_key (struct gcm_key *ctx, const union nettle_block16 *key)
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0
{
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  /* Table elements hold the key, premultiplied by all needed powers
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     of x. Element ordering follows the order bits are processed in
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     _ghash_update, alternating u64[0] and u64[1] bits, starting from
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     the least significant end. In the gcm bit order, bits (left to
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     right) correspond to x powers (the numbers) like
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       |0...7|8...15|...|56...63|64...71|72...79|...|120...127|
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     where | indicates the byte boundaries. On little endian, these
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     bits are in u64 like
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       u64[0]: | 56...63   48...55   40...47  32...39  24...31 16...23  8...15  0...7|
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       u64[1]: |120...127 112...129 104...111 96...103 88...95 80...87 72...79 64...71|
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     With big-endian, we instead get
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       u64[0]:  |0...63|
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       u64[1]: |64...127|
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  */
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#if WORDS_BIGENDIAN
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# define INDEX_PERMUTE 63
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#else
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# define INDEX_PERMUTE 7
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#endif
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  unsigned i;
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  block16_set (&ctx->h[2*INDEX_PERMUTE], key);
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  for (i = 1; i < 64; i++)
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    block16_mulx_ghash(&ctx->h[2*(i ^ INDEX_PERMUTE)], &ctx->h[2*((i-1) ^ INDEX_PERMUTE)]);
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  block16_mulx_ghash(&ctx->h[2*INDEX_PERMUTE + 1], &ctx->h[2*(63^INDEX_PERMUTE)]);
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  for (i = 1; i < 64; i++)
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    block16_mulx_ghash(&ctx->h[2*(i ^ INDEX_PERMUTE)+1], &ctx->h[2*((i-1) ^ INDEX_PERMUTE)+1]);
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0
}