src/shared/libosmocore/include/osmocom/gsm/a5.h

   1 /*
   2  * a5.h
   3  *
   4  * Copyright (C) 2011  Sylvain Munaut <tnt@246tNt.com>
   5  *
   6  * All Rights Reserved
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  */
  22
  23 #ifndef __OSMO_A5_H__
  24 #define __OSMO_A5_H__
  25
  26 #include <stdint.h>
  27
  28 #include <osmocom/core/bits.h>
  29
  30 /*! \defgroup a5 GSM A5 ciphering algorithm
  31  *  @{
  32  */
  33
  34 /*! \file gsm/a5.h
  35  *  \brief Osmocom GSM A5 ciphering algorithm header
  36  */
  37
  38 /*! \brief Converts a frame number into the 22 bit number used in A5/x
  39  *  \param[in] fn The true framenumber
  40  *  \return 22 bit word
  41  */
  42 static inline uint32_t
  43 osmo_a5_fn_count(uint32_t fn)
  44 {
  45         int t1 = fn / (26 * 51);
  46         int t2 = fn % 26;
  47         int t3 = fn % 51;
  48         return (t1 << 11) | (t3 << 5) | t2;
  49 }
  50
  51         /* Notes:
  52          *  - key must be 8 bytes long (or NULL for A5/0)
  53          *  - the dl and ul pointer must be either NULL or 114 bits long
  54          *  - fn is the _real_ GSM frame number.
  55          *    (converted internally to fn_count)
  56          */
  57 void osmo_a5(int n, const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul);
  58 void osmo_a5_1(const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul);
  59 void osmo_a5_2(const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul);
  60
  61 /*! @} */
  62
  63 #endif /* __OSMO_A5_H__ */