FIX: `lf visa2000` - identified unknown nibble in checksum. Is not checksum, but...

diff --git a/client/cmdlfvisa2000.c b/client/cmdlfvisa2000.c
index 5c030ec3b83c18570404553391e58910ffbe2938..26b447a4323156160fddff44da383b1bb71549c8 100644 (file)
--- a/client/cmdlfvisa2000.c
+++ b/client/cmdlfvisa2000.c
@@ -45,6 +45,23 @@ static uint8_t visa_chksum( uint32_t id ) {
     return sum & 0xF;
 }
 
+static uint8_t visa_parity( uint32_t id) {
+       // 4bit parity LUT
+       uint8_t par_lut[] = {
+               0,1,1,0
+               ,1,0,0,1
+               ,1,0,0,1
+               ,0,1,1,0
+       };      
+       uint8_t par = 0;
+       par |= par_lut[ NIBBLE_HIGH( (id >> 8) & 0xFF) ] << 3;
+       par |= par_lut[ NIBBLE_LOW( (id >> 8) & 0xFF) ] << 2;
+       par |= par_lut[ NIBBLE_HIGH( id & 0xFF ) ] << 1;
+       par |= par_lut[ NIBBLE_LOW( id & 0xFF) ];
+       return par;     
+}
+
+
 /**
 *
 * 56495332 00096ebd 00000077 —> tag id 618173
@@ -98,12 +115,21 @@ int CmdVisa2kDemod(const char *Cmd) {
        // chksum
        uint8_t calc = visa_chksum(raw2);
        uint8_t chk = raw3 & 0xF;       
+               
        // test checksums
        if ( chk != calc ) { 
                printf("DEBUG: error: Visa2000 checksum failed %x - %x\n", chk, calc);
                save_restoreGB(0);
                return 0;
        }
+       // parity
+       uint8_t calc_par = visa_parity(raw2);
+       uint8_t chk_par = (raw3 & 0xF0) >> 4;
+       if ( calc_par != chk_par) {
+               printf("DEBUG: error: Visa2000 parity failed %x - %x\n", chk_par, calc_par);
+               save_restoreGB(0);
+               return 0;               
+       }
        PrintAndLog("Visa2000 Tag Found: Card ID %u,  Raw: %08X%08X%08X", raw2,  raw1 ,raw2, raw3);
        save_restoreGB(0);
        return 1;
@@ -133,7 +159,7 @@ int CmdVisa2kClone(const char *Cmd) {
        
        // 
        blocks[2] = id;
-       blocks[3] = visa_chksum(id);
+       blocks[3] =  (visa_parity(id) << 4) | visa_chksum(id);  
 
        PrintAndLog("Preparing to clone Visa2000 to T55x7 with CardId: %u", id);
        PrintAndLog("Blk | Data ");
@@ -175,7 +201,7 @@ int CmdVisa2kSim(const char *Cmd) {
 
        UsbCommand c = {CMD_ASK_SIM_TAG, {arg1, arg2, size}};
 
-       uint32_t blocks[3] = { BL0CK1, id,  visa_chksum(id) };
+       uint32_t blocks[3] = { BL0CK1, id, (visa_parity(id) << 4) | visa_chksum(id) };
 
        for(int i=0; i<3; ++i)
                num_to_bytebits(blocks[i], 32, c.d.asBytes + i*32);