52 lines
3.0 KiB
C
52 lines
3.0 KiB
C
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ 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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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/crypto/rijndael.h"
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#include "libc/dce.h"
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static noinline aes_block_t xtime(aes_block_t x) {
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return ((x ^ (x & 0x80808080)) << 1) ^ (((x & 0x80808080) >> 7) * 0x1b);
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}
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static aes_block_t gf256mulx4(aes_block_t x, aes_block_t c) {
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return ((((c >> 0 & 0x01010101) * 0xff) & x) ^
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(((c >> 1 & 0x01010101) * 0xff) & xtime(x)) ^
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(((c >> 2 & 0x01010101) * 0xff) & xtime(xtime(x))) ^
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(((c >> 3 & 0x01010101) * 0xff) & xtime(xtime(xtime(x)))) ^
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(((c >> 4 & 0x01010101) * 0xff) & xtime(xtime(xtime(x)))));
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}
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/**
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* Applies inverse of Rijndael MixColumns() transformation.
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* @see FIPS-197
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*/
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aes_block_t InvMixColumns(aes_block_t x) {
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uint32_t i;
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aes_block_t y = {0, 0, 0, 0};
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aes_block_t c = {0x090D0B0E, 0x090D0B0E, 0x090D0B0E, 0x090D0B0E};
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for (i = 0; i < 4; ++i) {
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y ^= gf256mulx4((x & 0xff) * 0x01010101,
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(((c >> 000) & 0xff) << 000 | ((c >> 010) & 0xff) << 030 |
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((c >> 020) & 0xff) << 020 | ((c >> 030) & 0xff) << 010));
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x = x << 8 | x >> 24;
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c = c << 8 | c >> 24;
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}
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return y;
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}
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