Add 2 files for multiplication in GF(128)

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
This commit is contained in:
Aorimn 2016-01-31 12:08:23 +01:00 committed by Jaeden Amero
parent 9f52aebe2e
commit b053658f95
3 changed files with 125 additions and 0 deletions

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@ -0,0 +1,46 @@
/**
* \file gf128mul.h
*
* \brief Fast multiplication in GF(128)
*
* 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)
*/
#ifndef MBEDTLS_GF128MUL_H
#define MBEDTLS_GF128MUL_H
#ifdef __cplusplus
extern "C" {
#endif
/**
* \brief Big-Endian definition for 128 bits elements
*/
typedef unsigned char be128[16];
/**
* \brief Multiplication in GF(128):
* r = x times x^4 times x^8 in GF(2^128)
*
* \param x the 128-bits number you want to multiply
* \param r result
*/
void gf128mul_x_ble(be128 r, const be128 x);
#endif /* gf128mul.h */

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@ -29,6 +29,7 @@ set(src_crypto
entropy_poll.c
error.c
gcm.c
gf128mul.c
havege.c
hkdf.c
hmac_drbg.c

78
library/gf128mul.c Normal file
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/*
* 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);
}