flaneth

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/* flaneth - flash and ethernet - dartboard mod
 * version 0.1 date 2008-11-09
 * Copyright (C) 2007-2008 Stefan Schuermans <stefan@schuermans.info>
 * Copyleft: GNU public license V2 - http://www.gnu.org/copyleft/gpl.html
 * a BlinkenArea project - http://www.blinkenarea.org/
 */
#include <stdint.h>
#include "xtea.h"
#define delta 0x9E3779B9
// XTEA encrypt a block of 64 bits
// - this is not block XTEA, it's the basic XTEA algorithm
static void xtea_enc_block( uint32_t key[4], uint8_t rounds, uint32_t in[2], uint32_t out[2] )
{
  uint32_t y, z, sum;
  y = in[0];
  z = in[1];
  sum = 0;
  for( ; rounds > 0; rounds-- )
  {
    y += ((z << 4 ^ z >> 5) + z) ^ (sum + key[sum & 3]);
    sum += delta;
    z += ((y << 4 ^ y >> 5) + y) ^ (sum + key[sum >> 11 & 3]);
  }
  out[0] = y;
  out[1] = z;
}
// XTEA decrypt a block of 64 bits
// - this is not block XTEA, it's the basic XTEA algorithm
static void xtea_dec_block( uint32_t key[4], uint8_t rounds, uint32_t in[2], uint32_t out[2] )
{
  uint32_t y, z, sum;
  y = in[0];
  z = in[1];
  sum = (uint32_t)delta * rounds;
  for( ; rounds > 0; rounds-- )
  {
    z -= ((y << 4 ^ y >> 5) + y) ^ (sum + key[sum >> 11 & 3]);
    sum -= delta;
    y -= ((z << 4 ^ z >> 5) + z) ^ (sum + key[sum & 3]);
  }
  out[0] = y;
  out[1] = z;
}
 
 
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