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
  14 void tea_encrypt(uint8_t *v, uint8_t *key) {
  15
  16         uint32_t a=0,b=0,c=0,d=0,y=0,z=0;
  17         uint32_t sum = 0;
  18         uint8_t n = ROUNDS;
  19
  20         //key
  21         a = bytes_to_num(key, 4);
  22         b = bytes_to_num(key+4, 4);
  23         c = bytes_to_num(key+8, 4);
  24         d = bytes_to_num(key+12, 4);
  25
  26         //input
  27         y = bytes_to_num(v, 4);
  28         z = bytes_to_num(v+4, 4);
  29
  30         while ( n-- > 0 ) {
  31                 sum += DELTA;
  32                 y += ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
  33                 z += ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
  34         }
  35
  36         num_to_bytes(y, 4, v);
  37         num_to_bytes(z, 4, v+4);
  38 }
  39
  40 void tea_decrypt(uint8_t *v, uint8_t *key) {
  41
  42         uint32_t a=0,b=0,c=0,d=0,y=0,z=0;
  43         uint32_t sum = SUM;
  44         uint8_t n = ROUNDS;
  45
  46         //key
  47         a = bytes_to_num(key, 4);
  48         b = bytes_to_num(key+4, 4);
  49         c = bytes_to_num(key+8, 4);
  50         d = bytes_to_num(key+12, 4);
  51
  52         //input
  53         y = bytes_to_num(v, 4);
  54         z = bytes_to_num(v+4, 4);
  55
  56         /* sum = delta<<5, in general sum = delta * n */
  57         while ( n-- > 0 ) {
  58                 z -= ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
  59                 y -= ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
  60                 sum -= DELTA;
  61         }
  62         num_to_bytes(y, 4, v);
  63         num_to_bytes(z, 4, v+4);
  64 }