78 lines
1.4 KiB
C
78 lines
1.4 KiB
C
#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <inttypes.h>
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#include "rc4.h"
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struct tr_rc4_s
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{
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uint8_t x;
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uint8_t y;
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uint8_t state[256];
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};
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static void
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swapByte( uint8_t* a, uint8_t* b )
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{
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const uint8_t tmp = *a;
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*a = *b;
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*b = tmp;
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}
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tr_rc4_t *
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tr_rc4New ( const uint8_t * key,
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int keylen )
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{
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uint8_t index1 = 0;
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uint8_t index2 = 0;
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uint8_t * state;
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int i;
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tr_rc4_t * ret = calloc( 1, sizeof(tr_rc4_t) );
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/* initialize the state array */
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state = ret->state;
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for( i=0; i<256; ++i )
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state[i] = (uint8_t)i;
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ret->x = 0;
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ret->y = 0;
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for( i=0; i<256; ++i )
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{
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index2 = (key[index1] + state[i] + index2) % 256;
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swapByte (state+i, state+index2);
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index1 = (index1 + 1) % keylen;
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}
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return ret;
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}
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void
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tr_rc4Free( tr_rc4_t * rc4 )
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{
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free( rc4 );
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}
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void
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tr_rc4Step( tr_rc4_t * key,
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uint8_t * buf,
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int buflen )
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{
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uint8_t x = key->x;
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uint8_t y = key->y;
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uint8_t * state = key->state;
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uint8_t xorIndex;
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int i;
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for( i=0; i<buflen; ++i )
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{
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x = (x + 1) % 256;
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y = (state[x] + y) % 256;
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swapByte( state+x, state+y );
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xorIndex = (state[x] + state[y]) % 256;
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buf[i] ^= state[xorIndex];
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}
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key->x = x;
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key->y = y;
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}
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