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

[proxmark3-svn] / common / crc.c

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;
+}