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/*
* a5.h
*
* Copyright (C) 2011 Sylvain Munaut <tnt@246tNt.com>
*
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of 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.
*
* This program 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 a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#pragma once
#include <stdint.h>
#include <osmocom/core/bits.h>
/*! \defgroup a5 GSM A5 ciphering algorithm
* @{
*/
/*! \file gsm/a5.h
* \brief Osmocom GSM A5 ciphering algorithm header
*/
/*! \brief Converts a frame number into the 22 bit number used in A5/x
* \param[in] fn The true framenumber
* \return 22 bit word
*/
static inline uint32_t
osmo_a5_fn_count(uint32_t fn)
{
int t1 = fn / (26 * 51);
int t2 = fn % 26;
int t3 = fn % 51;
return (t1 << 11) | (t3 << 5) | t2;
}
/* Notes:
* - key must be 8 or 16 (for a5/4) bytes long (or NULL for A5/0)
* - the dl and ul pointer must be either NULL or 114 bits long
* - fn is the _real_ GSM frame number.
* (converted internally to fn_count)
*/
int osmo_a5(int n, const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul);
void osmo_a5_1(const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul);
void osmo_a5_2(const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul);
/*! @} */
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