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
  19 #ifndef __OSMO_A5_H__
  20 #define __OSMO_A5_H__
  21
  22 #include <stdint.h>
  23
  24 #include <osmocom/core/bits.h>
  25
  26 /*! \defgroup a5 GSM A5 ciphering algorithm
  27  *  @{
  28  */
  29
  30 /*! \file gsm/a5.h
  31  *  \brief Osmocom GSM A5 ciphering algorithm header
  32  */
  33
  34 /*! \brief Converts a frame number into the 22 bit number used in A5/x
  35  *  \param[in] fn The true framenumber
  36  *  \return 22 bit word
  37  */
  38 static inline uint32_t
  39 osmo_a5_fn_count(uint32_t fn)
  40 {
  41         int t1 = fn / (26 * 51);
  42         int t2 = fn % 26;
  43         int t3 = fn % 51;
  44         return (t1 << 11) | (t3 << 5) | t2;
  45 }
  46
  47         /* Notes:
  48          *  - key must be 8 bytes long (or NULL for A5/0)
  49          *  - the dl and ul pointer must be either NULL or 114 bits long
  50          *  - fn is the _real_ GSM frame number.
  51          *    (converted internally to fn_count)
  52          */
  53 void osmo_a5(int n, const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul);
  54 void osmo_a5_1(const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul);
  55 void osmo_a5_2(const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul);
  56
  57 /*! @} */
  58
  59 #endif /* __OSMO_A5_H__ */