FIX: legic_prng.c according to user on forum ref: http://www.proxmark.org/forum...

ADD:  method for calculating the storage crc8.

diff --git a/common/crc.c b/common/crc.c
index 0c73474fa75888bf40878f4b41d6269e7f74510c..21019da9c0b97891d8717779e0bf7d5538924f7b 100644 (file)
--- a/common/crc.c
+++ b/common/crc.c
@@ -6,6 +6,8 @@
 // Generic CRC calculation code.
 //-----------------------------------------------------------------------------
 #include "crc.h"
+#include "util.h"
+#include <stdio.h>
 #include <stdint.h>
 #include <stddef.h>
 
@@ -21,8 +23,7 @@ void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, u
 
 void crc_update(crc_t *crc, uint32_t data, int data_width)
 {
-       int i;
-       for(i=0; i<data_width; i++) {
+       for( int i=0; i < data_width; i++) {
                int oldstate = crc->state;
                crc->state = crc->state >> 1;
                if( (oldstate^data) & 1 ) {
@@ -49,8 +50,28 @@ uint32_t CRC8Maxim(uint8_t *buff, size_t size)
        crc_init(&crc, 9, 0x8c, 0x00, 0x00);
        crc_clear(&crc);
 
-       for (size_t i=0; i < size; ++i){
+       for (size_t i=0; i < size; ++i)
                crc_update(&crc, buff[i], 8);
-       }
+
        return crc_finish(&crc);
 }
+
+uint32_t CRC8Legic(uint8_t *buff, size_t size) {
+
+       // Poly 0x63,   reversed poly 0xC6,  Init 0x55,  Final 0x00
+       crc_t crc;
+       crc_init(&crc, 8, 0xC6, 0x55, 0);
+       crc_clear(&crc);
+       
+       for ( int i = 0; i < size; ++i)
+               crc_update(&crc, buff[i], 8);
+       return SwapBits(crc_finish(&crc), 8);
+}
+
+uint32_t SwapBits(uint32_t value, int nrbits) {
+       uint32_t newvalue = 0;
+       for(int i = 0; i < nrbits; i++) {
+               newvalue ^= ((value >> i) & 1) << (nrbits - 1 - i);
+       }
+       return newvalue;
+}

diff --git a/common/crc.h b/common/crc.h
index adbfb237c8cd3671dc26db260833af94c6188640..0c0770a47d9ea81820dcc40606f3e3d0ae15ca85 100644 (file)
--- a/common/crc.h
+++ b/common/crc.h
@@ -26,7 +26,7 @@ typedef struct crc {
  * final_xor is XORed onto the state before returning it from crc_result(). */
 extern void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor);
 
-/* Update the crc state. data is the data of length data_width bits (only the the
+/* Update the crc state. data is the data of length data_width bits (only the
  * data_width lower-most bits are used).
  */
 extern void crc_update(crc_t *crc, uint32_t data, int data_width);
@@ -38,7 +38,12 @@ extern void crc_clear(crc_t *crc);
 extern uint32_t crc_finish(crc_t *crc);
 
 // Calculate CRC-8/Maxim checksum
-uint32_t CRC8Maxim(uint8_t *buff, size_t size  );
+uint32_t CRC8Maxim(uint8_t *buff, size_t size);
+
+// Calculate CRC-8/Legic checksum
+uint32_t CRC8Legic(uint8_t *buff, size_t size);
+uint32_t SwapBits(uint32_t value, int nrbits);
+
 /* Static initialization of a crc structure */
 #define CRC_INITIALIZER(_order, _polynom, _initial_value, _final_xor) { \
        .state = ((_initial_value) & ((1L<<(_order))-1)), \

diff --git a/common/legic_prng.c b/common/legic_prng.c
index 4f3b1ffee1167ab51a067502451cb4e634c88cef..1f12873c2dd8e696e16adfd21139d6702cc932c6 100644 (file)
--- a/common/legic_prng.c
+++ b/common/legic_prng.c
@@ -26,7 +26,9 @@ void legic_prng_init(uint8_t init) {
 void legic_prng_forward(int count) {
   lfsr.c += count;
   while(count--) {
-    lfsr.a = lfsr.a >> 1 | (lfsr.a ^ lfsr.a >> 6) << 6;
+    //lfsr.a = lfsr.a >> 1 | (lfsr.a ^ lfsr.a >> 6) << 6;
+       // According: http://www.proxmark.org/forum/viewtopic.php?pid=5437#p5437
+       lfsr.a = (lfsr.a >> 1 | (lfsr.a ^ lfsr.a >> 6) << 6) & 0x7F;
     lfsr.b = lfsr.b >> 1 | (lfsr.b ^ lfsr.b >> 2 ^ lfsr.b >> 3 ^ lfsr.b >> 7) << 7;
   }
 }