client/src/tea.c

   1 //-----------------------------------------------------------------------------
   2 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
   3 // at your option, any later version. See the LICENSE.txt file for the text of
   4 // the license.
   5 //-----------------------------------------------------------------------------
   6 // Generic TEA crypto code.
   7 // ref: http://143.53.36.235:8080/source.htm#ansi
   8 //-----------------------------------------------------------------------------
   9 #include "tea.h"
  10
  11 #include "commonutil.h" // bytes_to_num etc
  12
  13 #define ROUNDS 32
  14 #define DELTA  0x9E3779B9
  15 #define SUM    0xC6EF3720
  16
  17 void tea_encrypt(uint8_t *v, uint8_t *key) {
  18
  19     uint32_t a = 0, b = 0, c = 0, d = 0, y = 0, z = 0;
  20     uint32_t sum = 0;
  21     uint8_t n = ROUNDS;
  22
  23     //key
  24     a = bytes_to_num(key, 4);
  25     b = bytes_to_num(key + 4, 4);
  26     c = bytes_to_num(key + 8, 4);
  27     d = bytes_to_num(key + 12, 4);
  28
  29     //input
  30     y = bytes_to_num(v, 4);
  31     z = bytes_to_num(v + 4, 4);
  32
  33     while (n-- > 0) {
  34         sum += DELTA;
  35         y += ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
  36         z += ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
  37     }
  38
  39     num_to_bytes(y, 4, v);
  40     num_to_bytes(z, 4, v + 4);
  41 }
  42
  43 void tea_decrypt(uint8_t *v, uint8_t *key) {
  44
  45     uint32_t a = 0, b = 0, c = 0, d = 0, y = 0, z = 0;
  46     uint32_t sum = SUM;
  47     uint8_t n = ROUNDS;
  48
  49     //key
  50     a = bytes_to_num(key, 4);
  51     b = bytes_to_num(key + 4, 4);
  52     c = bytes_to_num(key + 8, 4);
  53     d = bytes_to_num(key + 12, 4);
  54
  55     //input
  56     y = bytes_to_num(v, 4);
  57     z = bytes_to_num(v + 4, 4);
  58
  59     /* sum = delta<<5, in general sum = delta * n */
  60     while (n-- > 0) {
  61         z -= ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
  62         y -= ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
  63         sum -= DELTA;
  64     }
  65     num_to_bytes(y, 4, v);
  66     num_to_bytes(z, 4, v + 4);
  67 }