keygen.c File Reference

Implementation of A5/2 keystream generation. More...

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "utils.h"
#include "keygen.h"

Functions
void	keygen_clockReg (const int index)
	Clock the specified register.
void	keygen_clockingUnit (int clockAll)
	Performs register clocking according to the rules of the Clocking Unit.
byte	keygen_getOutBit ()
	Returns the current out keystream bit.
void	keysetup (const byte Kc[SECRETKEY_BITS], const byte frameId[FRAMEID_BITS])
	Initializes the whole system according to the keysetup procedure.
void	getKeystream (byte keystream[], const int len)
	Generates the desired amount of keystream.
int	keygen_test ()
	Autotests the key generation on a verified set.
Variables
byte	R1 [R1_BITS]
	LFSRs Storage (as global variables for easier exploitation)
byte	R2 [R2_BITS]
	LFSRs Storage (as global variables for easier exploitation)
byte	R3 [R3_BITS]
	LFSRs Storage (as global variables for easier exploitation)
byte	R4 [R4_BITS]
	LFSRs Storage (as global variables for easier exploitation)

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Detailed Description

Implementation of A5/2 keystream generation.

Author:

Nicolas Paglieri & Olivier Benjamin

Version:

File Revision #10

Date:

24/06/2011

Here are located the methods used for simulating the behavior of the A5/2 keystream generator. Four LFSRs are used... TODO: Write some more documentation

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Function Documentation

void getKeystream	(	byte	keystream[],
		const int	len
	)

Generates the desired amount of keystream.

Parameters:

[out]	keystream	Keystream to be generated
[in]	len	desired amount of keystream bits

References keygen_clockingUnit(), and keygen_getOutBit().

Referenced by attack_test(), keygen_test(), main(), and matrices_generation_test().

void keygen_clockingUnit

(

int

clockAll

)

Performs register clocking according to the rules of the Clocking Unit.

Parameters:

[in]

clockAll

When non-zero, bypass Clocking Unit decision: always clock (initialization phase)

References keygen_clockReg(), MAJORITY, R4, R4_CLOCKTAP_R1, R4_CLOCKTAP_R2, and R4_CLOCKTAP_R3.

Referenced by getKeystream(), and keysetup().

void keygen_clockReg

(

const int

index

)

Clock the specified register.

Parameters:

[in]

index

Register to be clocked

References DEBUG, R1, R1_BITS, R1_SHIFTTAP_1, R1_SHIFTTAP_2, R1_SHIFTTAP_3, R1_SHIFTTAP_4, R2, R2_BITS, R2_SHIFTTAP_1, R2_SHIFTTAP_2, R3, R3_BITS, R3_SHIFTTAP_1, R3_SHIFTTAP_2, R3_SHIFTTAP_3, R3_SHIFTTAP_4, R4, R4_BITS, R4_SHIFTTAP_1, and R4_SHIFTTAP_2.

Referenced by keygen_clockingUnit().

int keygen_test

(

)

Autotests the key generation on a verified set.

Returns:

0 if the test is successfull, non-zero otherwise

References DEBUG, FRAMEID_BITS, getKeystream(), keysetup(), and SECRETKEY_BITS.

Referenced by main().

void keysetup	(	const byte	Kc[SECRETKEY_BITS],
		const byte	frameId[FRAMEID_BITS]
	)

Initializes the whole system according to the keysetup procedure.

Parameters:

[in]	Kc	Secret Key
[in]	frameId	Frame Id

References FRAMEID_BITS, keygen_clockingUnit(), R1, R1_BITS, R1_INITIAL_CONST_POS, R2, R2_BITS, R2_INITIAL_CONST_POS, R3, R3_BITS, R3_INITIAL_CONST_POS, R4, R4_BITS, R4_INITIAL_CONST_POS, and SECRETKEY_BITS.

Referenced by attack_test(), keygen_test(), main(), and matrices_generation_test().