tea.c

#include "tea.h"
/*************************************************/
void encryptBlock(uint8_t * data, uint32_t * key)
{
  uint32_t i, blocks;
  uint32_t* data32;
  data32 = (uint32_t *) data;
  flipBytes(data32);
  for (i = 0; i < 2; i++)
  {
    encrypt(&data32[i * 2], key);
  }
}
/*************************************************/
void decryptBlock(uint8_t * data, uint32_t * key)
{
  uint32_t i, blocks;
  uint32_t* data32;
  data32 = (uint32_t *) data;
  flipBytes(data32);
  for (i = 0; i < 2; i++)
  {
    decrypt(&data32[i * 2], key);
  }
}
/*************************************************/
/* encrypt
 *   Encrypt 64 bits with a 128 bit key using TEA
 *   From http://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm
 * Arguments:
 *   v - array of two 32 bit uints to be encoded in place
 *   k - array of four 32 bit uints to act as key
 * Returns:
 *   v - encrypted result
 * Side effects:
 *   None
 */
void encrypt (uint32_t* v, uint32_t* k)
{
  /* set up */
  uint32_t v0 = v[0];
  uint32_t v1 = v[1];
  uint32_t sum = 0;
  uint32_t i;

  /* a key schedule constant */
  uint32_t delta = 0x9e3779b9;

  /* cache key */
  uint32_t k0 = k[0];
  uint32_t k1 = k[1];
  uint32_t k2 = k[2];
  uint32_t k3 = k[3];

  /* basic cycle start */
  for (i = 0; i < 32; i++)
  {
    sum += delta;
    v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
    v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
  }
  /* end cycle */

  v[0] = v0;
  v[1] = v1;
}

void decrypt (uint32_t* v, uint32_t* k)
{
  /* set up */
  uint32_t v0 = v[0];
  uint32_t v1 = v[1];
  uint32_t sum = 0xC6EF3720;
  uint32_t i;

  /* a key schedule constant */
  uint32_t delta = 0x9e3779b9;

  /* cache key */
  uint32_t k0 = k[0];
  uint32_t k1 = k[1];
  uint32_t k2 = k[2];
  uint32_t k3 = k[3];

  /* basic cycle start */
  for (i = 0; i < 32; i++)
  {
    v1 -= ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
    v0 -= ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
    sum -= delta;
  }
  /* end cycle */

  v[0] = v0;
  v[1] = v1;
}