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#include "rc4.h"
static void
swap_byte (unsigned char *a, unsigned char *b)
{
unsigned char swapByte;
swapByte = *a;
*a = *b;
*b = swapByte;
}
void
prepare_key (unsigned char *key_data_ptr, int key_data_len, RC4_KEY *key)
{
unsigned char index1;
unsigned char index2;
unsigned char *state;
unsigned int counter;
state = &key->state[0];
for (counter = 0; counter < 256; counter++)
state[counter] = counter;
key->x = 0;
key->y = 0;
index1 = 0;
index2 = 0;
for (counter = 0; counter < 256; counter++)
{
index2 = (key_data_ptr[index1] + state[counter] + index2) % 256;
swap_byte (&state[counter], &state[index2]);
index1 = (index1 + 1) % key_data_len;
}
}
void
rc4 (unsigned char *buffer_ptr, unsigned buffer_len, RC4_KEY *key)
{
unsigned char x;
unsigned char y;
unsigned char *state;
unsigned char xorIndex;
unsigned int counter;
x = key->x;
y = key->y;
state = key->state;
for (counter = 0; counter < buffer_len; counter++)
{
x = (x + 1) % 256;
y = (state[x] + y) % 256;
swap_byte (&state[x], &state[y]);
xorIndex = (state[x] + state[y]) % 256;
buffer_ptr[counter] ^= state[xorIndex];
}
key->x = x;
key->y = y;
}
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