A5 ciphering algorithm

Files
file	a5.h
	Osmocom GMR-1 A5 ciphering algorithm header.
file	a5.c
	Osmocom GMR-1 A5 ciphering algorithm implementation.

Macros
#define	A51_R1_LEN   19
#define	A51_R2_LEN   22
#define	A51_R3_LEN   23
#define	A51_R4_LEN   17
#define	A51_R1_MASK   ((1<<A51_R1_LEN)-1)
#define	A51_R2_MASK   ((1<<A51_R2_LEN)-1)
#define	A51_R3_MASK   ((1<<A51_R3_LEN)-1)
#define	A51_R4_MASK   ((1<<A51_R4_LEN)-1)
#define	A51_R1_TAPS   0x072000 /* x^19 + x^18 + x^17 + x^14 + 1 */
#define	A51_R2_TAPS   0x311000 /* x^22 + x^21 + x^17 + x^13 + 1 */
#define	A51_R3_TAPS   0x660000 /* x^23 + x^22 + x^19 + x^18 + 1 */
#define	A51_R4_TAPS   0x013100 /* x^17 + x^14 + x^13 + x^9 + 1 */
#define	A51_BIT(r, n)   (1 << n)

Functions
void	gmr1_a5 (int n, uint8_t *key, uint32_t fn, int nbits, ubit_t *dl, ubit_t *ul)
	Main method to generate a A5/x cipher stream. More...
void	gmr1_a5_1 (uint8_t *key, uint32_t fn, int nbits, ubit_t *dl, ubit_t *ul)
	Generate a GMR-1 A5/1 cipher stream. More...

Detailed Description

Function Documentation

gmr1_a5()

void gmr1_a5	(	int	n,
		uint8_t *	key,
		uint32_t	fn,
		int	nbits,
		ubit_t *	dl,
		ubit_t *	ul
	)

Main method to generate a A5/x cipher stream.

Parameters

[in]	n	Which A5/x method to use
[in]	key	8 byte array for the key (as received from the SIM)
[in]	fn	Frame number
[in]	nbits	How many bits to generate
[out]	dl	Pointer to array of ubits to return Downlink cipher stream
[out]	ul	Pointer to array of ubits to return Uplink cipher stream

Currently only A5/0 and A5/1. Either (or both) of dl/ul can be NULL if not needed.

References gmr1_a5_1().

gmr1_a5_1()

void gmr1_a5_1	(	uint8_t *	key,
		uint32_t	fn,
		int	nbits,
		ubit_t *	dl,
		ubit_t *	ul
	)

Generate a GMR-1 A5/1 cipher stream.

Parameters

[in]	key	8 byte array for the key (as received from the SIM)
[in]	fn	Frame number
[in]	nbits	How many bits to generate
[out]	dl	Pointer to array of ubits to return Downlink cipher stream
[out]	ul	Pointer to array of ubits to return Uplink cipher stream

Either (or both) of dl/ul can be NULL if not needed.

Referenced by gmr1_a5().