#include
#include “tests/arc4.h”
/* Swap bytes. */
static inline void
swap_byte (uint8_t *a, uint8_t *b)
{
uint8_t t = *a;
*a = *b;
*b = t;
}
void
arc4_init (struct arc4 *arc4, const void *key_, size_t size)
{
const uint8_t *key = key_;
size_t key_idx;
uint8_t *s;
int i, j;
s = arc4->s;
arc4->i = arc4->j = 0;
for (i = 0; i < 256; i++)
s[i] = i;
for (key_idx = 0, i = j = 0; i < 256; i++)
{
j = (j + s[i] + key[key_idx]) & 255;
swap_byte (s + i, s + j);
if (++key_idx >= size)
key_idx = 0;
}
}
void
arc4_crypt (struct arc4 *arc4, void *buf_, size_t size)
{
uint8_t *buf = buf_;
uint8_t *s;
uint8_t i, j;
s = arc4->s;
i = arc4->i;
j = arc4->j;
while (size– > 0)
{
i += 1;
j += s[i];
swap_byte (s + i, s + j);
*buf++ ^= s[(s[i] + s[j]) & 255];
}
arc4->i = i;
arc4->j = j;
}