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Rc4.c - Revision history
2026-05-12T11:58:53Z
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Grauel at 10:32, 31 October 2006
2006-10-31T10:32:03Z
<p></p>
<p><b>New page</b></p><div> /*rc4.c */<br />
#include "rc4.h"<br />
static void swap_byte(unsigned char *a, unsigned char *b);<br />
void prepare_key(unsigned char *key_data_ptr, int key_data_len,<br />
rc4_key *key)<br />
{<br />
unsigned char swapByte;<br />
unsigned char index1;<br />
unsigned char index2;<br />
unsigned char* state;<br />
short counter; <br />
<br />
state = &key->state[0]; <br />
for(counter = 0; counter < 256; counter++) <br />
state[counter] = counter; <br />
key->x = 0; <br />
key->y = 0; <br />
index1 = 0; <br />
index2 = 0; <br />
for(counter = 0; counter < 256; counter++) <br />
{ <br />
index2 = (key_data_ptr[index1] + state[counter] +<br />
index2) % 256; <br />
swap_byte(&state[counter], &state[index2]); <br />
<br />
index1 = (index1 + 1) % key_data_len; <br />
} <br />
}<br />
<br />
void rc4(unsigned char *buffer_ptr, int buffer_len, rc4_key *key)<br />
{<br />
unsigned char x;<br />
unsigned char y;<br />
unsigned char* state;<br />
unsigned char xorIndex;<br />
short counter; <br />
<br />
x = key->x; <br />
y = key->y; <br />
<br />
state = &key->state[0]; <br />
for(counter = 0; counter < buffer_len; counter ++) <br />
{ <br />
x = (x + 1) % 256; <br />
y = (state[x] + y) % 256; <br />
swap_byte(&state[x], &state[y]); <br />
<br />
xorIndex = (state[x] + state[y]) % 256; <br />
<br />
buffer_ptr[counter] ^= state[xorIndex]; <br />
} <br />
key->x = x; <br />
key->y = y;<br />
}<br />
<br />
static void swap_byte(unsigned char *a, unsigned char *b)<br />
{<br />
unsigned char swapByte;<br />
<br />
swapByte = *a;<br />
*a = *b; <br />
*b = swapByte;<br />
}</div>
Grauel