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/* rc4 */
#include "cipher-rc4.h"
static void swap_byte (unsigned char *a, unsigned char *b);
void
rc4_prepare_key (unsigned char *key_data_ptr, int key_data_len, rc4_key *key)
{
unsigned char i1, i2;
unsigned char * s;
short c;
s = &key->state[0];
for (c = 0; c < 256; c++)
s[c] = c;
key->x = key->y = 0;
i1 = i2 = 0;
for (c = 0; c < 256; c++) {
i2 = (key_data_ptr[i1] + s[c] + i2) % 256;
swap_byte (&s[c], &s[i2]);
i1 = (i1 + 1) % key_data_len;
}
}
void
rc4_encipher (unsigned char *buffer, unsigned long int buffer_len,
unsigned char *key, int key_len)
{
rc4_key key_r;
if (key == NULL || buffer == NULL || buffer_len == 0)
return;
rc4_prepare_key (key, key_len, &key_r);
rc4_cipher (buffer, buffer_len, &key_r);
return;
}
void
rc4_cipher (unsigned char *buffer_ptr, int buffer_len, rc4_key *key)
{
unsigned char x;
unsigned char y;
unsigned char *state;
unsigned char xi;
unsigned int 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;
swap_byte(&state[x], &state[y]);
xi = (state[x] + state[y]) % 256;
buffer_ptr[counter] ^= state[xi];
}
key->x = x;
key->y = y;
}
static void
swap_byte (unsigned char *a, unsigned char *b)
{
unsigned char sb;
sb = *a;
*a = *b;
*b = sb;
}
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