/* umac-l3.c

   Copyright (C) 2013 Niels Möller

   This file is part of GNU Nettle.

   GNU Nettle is free software: you can redistribute it and/or

   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free

       Software Foundation; either version 3 of the License, or (at your

       option) any later version.

   or

     * the GNU General Public License as published by the Free

       Software Foundation; either version 2 of the License, or (at your

       option) any later version.

   or both in parallel, as here.

   GNU Nettle 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

   General Public License for more details.

   You should have received copies of the GNU General Public License and

   the GNU Lesser General Public License along with this program.  If

   not, see http://www.gnu.org/licenses/.

*/

#if HAVE_CONFIG_H

# include "config.h"

#endif

#include "umac.h"

#include "umac-internal.h"

#include "macros.h"

/* 2^36 - 5 */

#define P 0x0000000FFFFFFFFBULL

#if WORDS_BIGENDIAN

#define BE_SWAP64(x) x

#else

#define BE_SWAP64(x)        \

  (((x & 0xff) << 56)       \

   | ((x & 0xff00) << 40)     \

   | ((x & 0xff0000) << 24)     \

   | ((x & 0xff000000) << 8)      \

   | ((x >> 8) & 0xff000000)      \

   | ((x >> 24) & 0xff0000)     \

   | ((x >> 40) & 0xff00)     \

   | (x >> 56) )

#endif

void

_nettle_umac_l3_init (unsigned size, uint64_t *k)

{

  unsigned i;

  for (i = 0; i < size; i++)

    {

      uint64_t w = k[i];

      w = BE_SWAP64 (w);

      k[i] = w % P;

    }

}

static uint64_t

umac_l3_word (const uint64_t *k, uint64_t w)

{

  unsigned i;

  uint64_t y;

  /* Since it's easiest to process the input word from the low end,

   * loop over keys in reverse order. */

  for (i = y = 0; i < 4; i++, w >>= 16)

    y += (w & 0xffff) * k[3-i];

  return y;

}

uint32_t

_nettle_umac_l3 (const uint64_t *key, const uint64_t *m)

{

  uint32_t y = (umac_l3_word (key, m[0])

    + umac_l3_word (key + 4, m[1])) % P;

#if !WORDS_BIGENDIAN

  y = ((ROTL32(8,  y) & 0x00FF00FFUL)

       | (ROTL32(24, y) & 0xFF00FF00UL));

#endif

  return y;

}