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/*
* Copyright (c) 2012 Vincent Hanquez <vincent@snarc.org>
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the author nor the names of his contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <stdio.h>
#include <stdint.h>
#include <cryptonite_cpu.h>
#include <aes/gf.h>
#include <aes/x86ni.h>
/* inplace GFMUL for xts mode */
void cryptonite_aes_generic_gf_mulx(block128 *a)
{
const uint64_t gf_mask = cpu_to_le64(0x8000000000000000ULL);
uint64_t r = ((a->q[1] & gf_mask) ? cpu_to_le64(0x87) : 0);
a->q[1] = cpu_to_le64((le64_to_cpu(a->q[1]) << 1) | (a->q[0] & gf_mask ? 1 : 0));
a->q[0] = cpu_to_le64(le64_to_cpu(a->q[0]) << 1) ^ r;
}
/*
* GF multiplication with Shoup's method and 4-bit table.
*
* We precompute the products of H with all 4-bit polynomials and store them in
* a 'table_4bit' array. To avoid unnecessary byte swapping, the 16 blocks are
* written to the table with qwords already converted to CPU order. Table
* indices use the reflected bit ordering, i.e. polynomials X^0, X^1, X^2, X^3
* map to bit positions 3, 2, 1, 0 respectively.
*
* To multiply an arbitrary block with H, the input block is decomposed in 4-bit
* segments. We get the final result after 32 table lookups and additions, one
* for each segment, interleaving multiplication by P(X)=X^4.
*/
/* convert block128 qwords between BE and CPU order */
static inline void block128_cpu_swap_be(block128 *a, const block128 *b)
{
a->q[1] = cpu_to_be64(b->q[1]);
a->q[0] = cpu_to_be64(b->q[0]);
}
/* multiplication by P(X)=X, assuming qwords already in CPU order */
static inline void cpu_gf_mulx(block128 *a, const block128 *b)
{
uint64_t v0 = b->q[0];
uint64_t v1 = b->q[1];
a->q[1] = v1 >> 1 | v0 << 63;
a->q[0] = v0 >> 1 ^ ((0-(v1 & 1)) & 0xe100000000000000ULL);
}
static const uint64_t r4_0[] =
{ 0x0000000000000000ULL, 0x1c20000000000000ULL
, 0x3840000000000000ULL, 0x2460000000000000ULL
, 0x7080000000000000ULL, 0x6ca0000000000000ULL
, 0x48c0000000000000ULL, 0x54e0000000000000ULL
, 0xe100000000000000ULL, 0xfd20000000000000ULL
, 0xd940000000000000ULL, 0xc560000000000000ULL
, 0x9180000000000000ULL, 0x8da0000000000000ULL
, 0xa9c0000000000000ULL, 0xb5e0000000000000ULL
};
/* multiplication by P(X)=X^4, assuming qwords already in CPU order */
static inline void cpu_gf_mulx4(block128 *a, const block128 *b)
{
uint64_t v0 = b->q[0];
uint64_t v1 = b->q[1];
a->q[1] = v1 >> 4 | v0 << 60;
a->q[0] = v0 >> 4 ^ r4_0[v1 & 0xf];
}
/* initialize the 4-bit table given H */
void cryptonite_aes_generic_hinit(table_4bit htable, const block128 *h)
{
block128 v, *p;
int i, j;
/* multiplication by 0 is 0 */
block128_zero(&htable[0]);
/* at index 8=2^3 we have H.X^0 = H */
i = 8;
block128_cpu_swap_be(&htable[i], h); /* in CPU order */
p = &htable[i];
/* for other powers of 2, repeat multiplication by P(X)=X */
for (i = 4; i > 0; i >>= 1)
{
cpu_gf_mulx(&htable[i], p);
p = &htable[i];
}
/* remaining elements are linear combinations */
for (i = 2; i < 16; i <<= 1) {
p = &htable[i];
v = *p;
for (j = 1; j < i; j++) {
p[j] = v;
block128_xor_aligned(&p[j], &htable[j]);
}
}
}
/* multiply a block with H */
void cryptonite_aes_generic_gf_mul(block128 *a, const table_4bit htable)
{
block128 b;
int i;
block128_zero(&b);
for (i = 15; i >= 0; i--)
{
uint8_t v = a->b[i];
block128_xor_aligned(&b, &htable[v & 0xf]); /* high bits (reflected) */
cpu_gf_mulx4(&b, &b);
block128_xor_aligned(&b, &htable[v >> 4]); /* low bits (reflected) */
if (i > 0)
cpu_gf_mulx4(&b, &b);
else
block128_cpu_swap_be(a, &b); /* restore BE order when done */
}
}
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