/* Implemented from David Sterndark's Sept 14, 1994 email */
#include "rc4.h"
void
prep_key(unsigned char *key_data_ptr, int key_data_len, RC4_KEY *key)
{
unsigned char swapByte;
unsigned char index1;
unsigned char index2;
unsigned char* state;
short 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;
swapByte = state[counter];
state[counter] = state[index2];
state[index2] = swapByte;
index1 = (index1 + 1) % key_data_len;
}
}
void
rc4(unsigned char *buffer_ptr, unsigned long buffer_len, RC4_KEY *key)
{
unsigned char x;
unsigned char y;
unsigned char* state;
unsigned char xorIndex;
unsigned char swapByte;
unsigned long counter;
x = key->x;
y = key->y;
state = &key->state[0];
for(counter = 0; counter < buffer_len; counter ++)
{
x = (x + 1) % 256;
y = (state[x] + y) % 256;
swapByte = state[x];
state[x] = state[y];
state[y] = swapByte;
xorIndex = (state[x] + state[y]) % 256;
buffer_ptr[counter] ^= state[xorIndex];
}
key->x = x;
key->y = y;
}