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/* umac-set-key.c
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2013 Niels Möller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02111-1301, USA.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <string.h>
#include "umac.h"
#include "macros.h"
static void
umac_kdf (struct aes_ctx *aes, unsigned index, unsigned length, uint8_t *dst)
{
uint8_t block[AES_BLOCK_SIZE];
uint64_t count;
WRITE_UINT64 (block, (uint64_t) index);
for (count = 1; length >= AES_BLOCK_SIZE;
length -= AES_BLOCK_SIZE, dst += AES_BLOCK_SIZE, count++)
{
WRITE_UINT64 (block + 8, count);
aes_encrypt (aes, AES_BLOCK_SIZE, dst, block);
}
if (length > 0)
{
WRITE_UINT64 (block + 8, count);
aes_encrypt (aes, AES_BLOCK_SIZE, block, block);
memcpy (dst, block, length);
}
}
#if WORDS_BIGENDIAN
#define BE_SWAP32(x) x
#define BE_SWAP32_N(n, x)
#else
#define BE_SWAP32(x) \
((ROTL32(8, x) & 0x00FF00FFUL) | \
(ROTL32(24, x) & 0xFF00FF00UL))
#define BE_SWAP32_N(n, x) do { \
unsigned be_i; \
for (be_i = 0; be_i < n; be_i++) \
{ \
uint32_t be_x = (x)[be_i]; \
(x)[be_i] = BE_SWAP32 (be_x); \
} \
} while (0)
#endif
void
_umac_set_key (uint32_t *l1_key, uint32_t *l2_key,
uint64_t *l3_key1, uint32_t *l3_key2,
struct aes_ctx *aes, const uint8_t *key, unsigned n)
{
unsigned size;
uint8_t buffer[UMAC_KEY_SIZE];
aes_set_encrypt_key (aes, UMAC_KEY_SIZE, key);
size = UMAC_DATA_SIZE / 4 + 4*(n-1);
umac_kdf (aes, 1, size * sizeof(uint32_t), (uint8_t *) l1_key);
BE_SWAP32_N (size, l1_key);
size = 6*n;
umac_kdf (aes, 2, size * sizeof(uint32_t), (uint8_t *) l2_key);
_umac_l2_init (size, l2_key);
size = 8*n;
umac_kdf (aes, 3, size * sizeof(uint64_t), (uint8_t *) l3_key1);
_umac_l3_init (size, l3_key1);
/* No need to byteswap these subkeys. */
umac_kdf (aes, 4, n * sizeof(uint32_t), (uint8_t *) l3_key2);
umac_kdf (aes, 0, UMAC_KEY_SIZE, buffer);
aes_set_encrypt_key (aes, UMAC_KEY_SIZE, buffer);
}
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