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I wonder what this is for.

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This commit is contained in:
Charles Kerr 2007-06-30 19:46:41 +00:00
parent 19c7d8367a
commit bacc2dc445
3 changed files with 94 additions and 2 deletions
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77
libtransmission/rc4.c Normal file
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@ -0,0 +1,77 @@
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
#include "rc4.h"
struct tr_rc4_s
{
uint8_t x;
uint8_t y;
uint8_t state[256];
};
static void
swapByte( uint8_t* a, uint8_t* b )
{
const uint8_t tmp = *a;
*a = *b;
*b = tmp;
}
tr_rc4_t *
tr_rc4New ( const uint8_t * key,
int keylen )
{
uint8_t index1 = 0;
uint8_t index2 = 0;
uint8_t * state;
int i;
tr_rc4_t * ret = calloc( 1, sizeof(tr_rc4_t) );
/* initialize the state array */
state = ret->state;
for( i=0; i<256; ++i )
state[i] = (uint8_t)i;
ret->x = 0;
ret->y = 0;
for( i=0; i<256; ++i )
{
index2 = (key[index1] + state[i] + index2) % 256;
swapByte (state+i, state+index2);
index1 = (index1 + 1) % keylen;
}
return ret;
}
void
tr_rc4Free( tr_rc4_t * rc4 )
{
free( rc4 );
}
void
tr_rc4Step( tr_rc4_t * key,
uint8_t * buf,
int buflen )
{
uint8_t x = key->x;
uint8_t y = key->y;
uint8_t * state = key->state;
uint8_t xorIndex;
int i;
for( i=0; i<buflen; ++i )
{
x = (x + 1) % 256;
y = (state[x] + y) % 256;
swapByte( state+x, state+y );
xorIndex = (state[x] + state[y]) % 256;
buf[i] ^= state[xorIndex];
}
key->x = x;
key->y = y;
}

15
libtransmission/rc4.h Normal file
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@ -0,0 +1,15 @@
#ifndef TR_RC4_H
#define TR_RC4_H
typedef struct tr_rc4_s tr_rc4_t;
tr_rc4_t * tr_rc4New ( const uint8_t * key,
int keylen );
void tr_rc4Step ( tr_rc4_t * rc4,
uint8_t * buf,
int buflen );
void tr_rc4Free ( tr_rc4_t * rc4 );
#endif

4
mk/lib.mk
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@ -5,8 +5,8 @@ include ../mk/common.mk
SRCS = bencode.c choking.c clients.c completion.c fastresume.c fdlimit.c \
http.c inout.c ipcparse.c makemeta.c metainfo.c natpmp.c net.c \
peer.c platform.c ratecontrol.c sha1.c shared.c strlcat.c strlcpy.c \
torrent.c tracker.c transmission.c upnp.c utils.c xml.c
peer.c platform.c ratecontrol.c rc4.c sha1.c shared.c strlcat.c \
strlcpy.c torrent.c tracker.c transmission.c upnp.c utils.c xml.c
OBJS = $(SRCS:%.c=%.o)