mirror of
https://github.com/yuzu-emu/mbedtls.git
synced 2024-11-29 16:04:23 +01:00
b053658f95
Multiplication in GF(128) is required by the AES-XEX mode for computing X in the XEX formula from https://en.wikipedia.org/wiki/Disk_encryption_theory#Xor-encrypt-xor_.28XEX.29
79 lines
2.7 KiB
C
79 lines
2.7 KiB
C
/*
|
|
* GF(2^128) multiplication functions
|
|
*
|
|
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
|
|
* SPDX-License-Identifier: Apache-2.0
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License"); you may
|
|
* not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*
|
|
* This file is part of mbed TLS (https://tls.mbed.org)
|
|
*/
|
|
#include <stdint.h>
|
|
|
|
#include "mbedtls/gf128mul.h"
|
|
|
|
/* Endianess with 64 bits values */
|
|
#ifndef GET_UINT64_LE
|
|
#define GET_UINT64_LE(n,b,i) \
|
|
{ \
|
|
(n) = ( (uint64_t) (b)[(i) + 7] << 56 ) \
|
|
| ( (uint64_t) (b)[(i) + 6] << 48 ) \
|
|
| ( (uint64_t) (b)[(i) + 5] << 40 ) \
|
|
| ( (uint64_t) (b)[(i) + 4] << 32 ) \
|
|
| ( (uint64_t) (b)[(i) + 3] << 24 ) \
|
|
| ( (uint64_t) (b)[(i) + 2] << 16 ) \
|
|
| ( (uint64_t) (b)[(i) + 1] << 8 ) \
|
|
| ( (uint64_t) (b)[(i) ] ); \
|
|
}
|
|
#endif
|
|
|
|
#ifndef PUT_UINT64_LE
|
|
#define PUT_UINT64_LE(n,b,i) \
|
|
{ \
|
|
(b)[(i) + 7] = (unsigned char) ( (n) >> 56 ); \
|
|
(b)[(i) + 6] = (unsigned char) ( (n) >> 48 ); \
|
|
(b)[(i) + 5] = (unsigned char) ( (n) >> 40 ); \
|
|
(b)[(i) + 4] = (unsigned char) ( (n) >> 32 ); \
|
|
(b)[(i) + 3] = (unsigned char) ( (n) >> 24 ); \
|
|
(b)[(i) + 2] = (unsigned char) ( (n) >> 16 ); \
|
|
(b)[(i) + 1] = (unsigned char) ( (n) >> 8 ); \
|
|
(b)[(i) ] = (unsigned char) ( (n) ); \
|
|
}
|
|
#endif
|
|
|
|
|
|
/* Jump table for not having ifs */
|
|
static const uint16_t gf128mul_table_bbe[2] = { 0x00, 0x87 };
|
|
|
|
|
|
/*
|
|
* This function multiply a field element by x, by x^4 and by x^8
|
|
* in the polynomial field representation. It uses 64-bit word operations
|
|
* to gain speed but compensates for machine endianess and hence works
|
|
* correctly on both styles of machine.
|
|
*/
|
|
void mbedtls_gf128mul_x_ble(mbedtls_be128 r, const mbedtls_be128 x)
|
|
{
|
|
uint64_t a, b, ra, rb;
|
|
|
|
GET_UINT64_LE(a, x, 0);
|
|
GET_UINT64_LE(b, x, 8);
|
|
|
|
ra = (a << 1) ^ gf128mul_table_bbe[b >> 63];
|
|
rb = (a >> 63) | (b << 1);
|
|
|
|
PUT_UINT64_LE(ra, r, 0);
|
|
PUT_UINT64_LE(rb, r, 8);
|
|
}
|
|
|