armsrc/optimized_cipher.h

   1 #ifndef OPTIMIZED_CIPHER_H
   2 #define OPTIMIZED_CIPHER_H
   3 #include <stdint.h>
   4
   5 /**
   6 * Definition 1 (Cipher state). A cipher state of iClass s is an element of F 40/2
   7 * consisting of the following four components:
   8 *       1. the left register l = (l 0 . . . l 7 ) ∈ F 8/2 ;
   9 *       2. the right register r = (r 0 . . . r 7 ) ∈ F 8/2 ;
  10 *       3. the top register t = (t 0 . . . t 15 ) ∈ F 16/2 .
  11 *       4. the bottom register b = (b 0 . . . b 7 ) ∈ F 8/2 .
  12 **/
  13 typedef struct {
  14         uint8_t l;
  15         uint8_t r;
  16         uint8_t b;
  17         uint16_t t;
  18 } State;
  19
  20 /** The reader MAC is MAC(key, CC * NR )
  21  **/
  22 void opt_doReaderMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4]);
  23 /**
  24  * The tag MAC is MAC(key, CC * NR * 32x0))
  25  */
  26 void opt_doTagMAC(uint8_t *cc_p, const uint8_t *div_key_p, uint8_t mac[4]);
  27
  28 /**
  29  * The tag MAC can be divided (both can, but no point in dividing the reader mac) into
  30  * two functions, since the first 8 bytes are known, we can pre-calculate the state
  31  * reached after feeding CC to the cipher.
  32  * @param cc_p
  33  * @param div_key_p
  34  * @return the cipher state
  35  */
  36 State opt_doTagMAC_1(uint8_t *cc_p, const uint8_t *div_key_p);
  37 /**
  38  * The second part of the tag MAC calculation, since the CC is already calculated into the state,
  39  * this function is fed only the NR, and internally feeds the remaining 32 0-bits to generate the tag
  40  * MAC response.
  41  * @param _init - precalculated cipher state
  42  * @param nr - the reader challenge
  43  * @param mac - where to store the MAC
  44  * @param div_key_p - the key to use
  45  */
  46 void opt_doTagMAC_2(State _init, uint8_t* nr, uint8_t mac[4], const uint8_t* div_key_p);
  47
  48 #endif // OPTIMIZED_CIPHER_H