asfcrypt.c File Reference

#include <stddef.h>
#include "libavutil/bswap.h"
#include "libavutil/des.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/mem.h"
#include "libavutil/rc4.h"
#include "asfcrypt.h"

Go to the source code of this file.

Functions
static uint32_t	inverse (uint32_t v)
	find multiplicative inverse modulo 2 ^ 32
static void	multiswap_init (const uint8_t keybuf[48], uint32_t keys[12])
	read keys from keybuf into keys
static void	multiswap_invert_keys (uint32_t keys[12])
	invert the keys so that encryption become decryption keys and the other way round.
static uint32_t	multiswap_step (const uint32_t keys[6], uint32_t v)
static uint32_t	multiswap_inv_step (const uint32_t keys[6], uint32_t v)
static uint64_t	multiswap_enc (const uint32_t keys[12], uint64_t key, uint64_t data)
	"MultiSwap" encryption
static uint64_t	multiswap_dec (const uint32_t keys[12], uint64_t key, uint64_t data)
	"MultiSwap" decryption
void	ff_asfcrypt_dec (const uint8_t key[20], uint8_t *data, int len)

Function Documentation

inverse()

static uint32_t inverse ( uint32_t v )

static

find multiplicative inverse modulo 2 ^ 32

Parameters

v	number to invert, must be odd!

Returns

number so that result * v = 1 (mod 2^32)

Definition at line 36 of file asfcrypt.c.

multiswap_init()

static void multiswap_init ( const uint8_t keybuf[48], uint32_t keys[12] )

static

read keys from keybuf into keys

Parameters

keybuf	buffer containing the keys
keys	output key array containing the keys for encryption in native endianness

Definition at line 55 of file asfcrypt.c.

Referenced by ff_asfcrypt_dec().

multiswap_invert_keys()

static void multiswap_invert_keys ( uint32_t keys[12] )

static

invert the keys so that encryption become decryption keys and the other way round.

Parameters

keys	key array of ints to invert

Definition at line 67 of file asfcrypt.c.

Referenced by ff_asfcrypt_dec().

multiswap_step()

static uint32_t multiswap_step ( const uint32_t keys[6], uint32_t v )

static

Definition at line 76 of file asfcrypt.c.

Referenced by multiswap_enc().

multiswap_inv_step()

static uint32_t multiswap_inv_step ( const uint32_t keys[6], uint32_t v )

static

Definition at line 88 of file asfcrypt.c.

Referenced by multiswap_dec().

multiswap_enc()

static uint64_t multiswap_enc ( const uint32_t keys[12], uint64_t key, uint64_t data )

static

"MultiSwap" encryption

Parameters

keys	32 bit numbers in machine endianness, 0-4 and 6-10 must be inverted from decryption
key	another key, this one must be the same for the decryption
data	data to encrypt

Returns

encrypted data

Definition at line 108 of file asfcrypt.c.

Referenced by ff_asfcrypt_dec().

multiswap_dec()

static uint64_t multiswap_dec ( const uint32_t keys[12], uint64_t key, uint64_t data )

static

"MultiSwap" decryption

Parameters

keys	32 bit numbers in machine endianness, 0-4 and 6-10 must be inverted from encryption
key	another key, this one must be the same as for the encryption
data	data to decrypt

Returns

decrypted data

Definition at line 132 of file asfcrypt.c.

Referenced by ff_asfcrypt_dec().

ff_asfcrypt_dec()

void ff_asfcrypt_dec	(	const uint8_t	key[20],
		uint8_t *	data,
		int	len )

Definition at line 148 of file asfcrypt.c.

Referenced by asf_parse_packet(), asf_read_multiple_payload(), and asf_read_single_payload().