git.zerfleddert.de Git - proxmark3-svn/blob - common/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 #define ROUNDS 32
  11 #define DELTA  0x9E3779B9
  12 #define SUM    0xC6EF3720
  13 #define SWAPENDIAN(x)\
  14   (x = (x >> 8 & 0xff00ff) | (x & 0xff00ff) << 8, x = x >> 16 | x << 16)
  15
  16 void tea_encrypt(uint8_t *v, uint8_t *key) {
  17
  18         uint32_t a=0,b=0,c=0,d=0,y=0,z=0;
  19         uint32_t sum = 0;
  20         uint8_t n = ROUNDS;
  21
  22         //key
  23         a = bytes_to_num(key, 4);
  24         b = bytes_to_num(key+4, 4);
  25         c = bytes_to_num(key+8, 4);
  26         d = bytes_to_num(key+12, 4);
  27
  28         //input
  29         y = bytes_to_num(v, 4);
  30         z = bytes_to_num(v+4, 4);
  31
  32         // SWAPENDIAN(a);
  33         // SWAPENDIAN(b);
  34         // SWAPENDIAN(c);
  35         // SWAPENDIAN(d);
  36         // SWAPENDIAN(y);
  37         // SWAPENDIAN(z);
  38
  39         while ( n-- > 0 ) {
  40                 sum += DELTA;
  41                 y += ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
  42                 z += ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
  43         }
  44
  45         // SWAPENDIAN(y);
  46         // SWAPENDIAN(z);
  47
  48         num_to_bytes(y, 4, v);
  49         num_to_bytes(z, 4, v+4);
  50 }
  51
  52 void tea_decrypt(uint8_t *v, uint8_t *key) {
  53
  54         uint32_t a=0,b=0,c=0,d=0,y=0,z=0;
  55         uint32_t sum = SUM;
  56         uint8_t n = ROUNDS;
  57
  58         //key
  59         a = bytes_to_num(key, 4);
  60         b = bytes_to_num(key+4, 4);
  61         c = bytes_to_num(key+8, 4);
  62         d = bytes_to_num(key+12, 4);
  63
  64         //input
  65         y = bytes_to_num(v, 4);
  66         z = bytes_to_num(v+4, 4);
  67
  68         // SWAPENDIAN(a);
  69         // SWAPENDIAN(b);
  70         // SWAPENDIAN(c);
  71         // SWAPENDIAN(d);
  72         // SWAPENDIAN(y);
  73         // SWAPENDIAN(z);
  74
  75         /* sum = delta<<5, in general sum = delta * n */
  76         while ( n-- > 0 ) {
  77                 z -= ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
  78                 y -= ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
  79                 sum -= DELTA;
  80         }
  81
  82         // SWAPENDIAN(y);
  83         // SWAPENDIAN(z);
  84         num_to_bytes(y, 4, v);
  85         num_to_bytes(z, 4, v+4);
  86 }