How to send the APDU command to get a success response? - javacard

Question

I have this method in my javacard applet:
public void process(APDU apdu)
{
byte[] buf = apdu.getBuffer() ;
switch(buf[ISO7816.OFFSET_INS])
{
case 0x40:
Util.arrayCopy(hello,(byte)0,buf,ISO7816.OFFSET_CDATA,(byte)5);
apdu.setOutgoingAndSend(ISO7816.OFFSET_CDATA,(byte)5);
break;
default: ISOException.throwIt(ISO7816.SW_WRONG_INS) ;
}
}
Here hello is :
private final static byte[] hello = {0x48, 0x65, 0x6c, 0x6c, 0x6f };
and I am sending the command in the script as follows:
powerup;
// Select the installer applet
0x00 0xA4 0x04 0x00 0x09 0xa0 0x00 0x00 0x00 0x62 0x03 0x01 0x08 0x01 0x7F;
// create TestApplet applet
0x80 0xB8 0x00 0x00 0xd 0xb 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x00 0x00 0x00 0x7F;
//show hello message
0x40 0x00 0x00 0x00; //this is the command mentioned in tutorial which gave error
powerdown;
The first two commands are succeeded, but the last one gets the error as the command is not in correct format .
I also tried this command:
0x00 0x40 0x00 0x00 0x00 0x7f;
But it gave me the response 6d00 which means INS vlaue not supported.
Here is the actual Response:
CLA: 80, INS:40, P1:00,P2:00,Lc:00,Le:00,SW1:6d,SW2:00
The expected response is to get the hello value along with the success reponse 9000
I am following the tutorial
What is the proper way to give the APDU command ?

Answer 1

As mentioned in the answer by #BzH, command 0x40 0x00 0x00 0x00 is not correct.
The correct command is
0x80 0x40 0x00 0x00 0x00.
There is one more problem: status word 6D00 is not sent by your applet, it is sent by the card manager applet with
AID = A00000006203010801
you have selected after powerup. The card manager applet does not know INS = 0x40 instruction, therefore the status code. You have to select your applet before sending any commands:
00 A4 04 00 [Lc] [... AID of your applet instance...]
80 40 00 00 00

Answer 2

The card's Global Platform class byte is 0x80. So you should send:
0x80 0x40 0x00 0x00 0x00
The first APDU you are sending 0x40 0x00 0x00 0x00 is wrong, because 0x40 is considered as the class byte and 0x00 as Instruction.

Answer 3

Finally this command worked for me.
As the APDU commands should be given in a format,
There are four cases to be followed , when sending commands to APDU:
Case Command data Expected response data
1 No data No data
2 No data Data
3 Data No data
4 Data Data
In case 1, the length Lc is null; therefore the Lc field and the data field are empty. The length Le is also null; therefore the Le field is empty. Consequently, the body is empty.
In case 2, the length Lc is null; therefore the Lc field and the data field are empty. The length of Le is not null; therefore the Le field is present. Consequently, the body consists of the Le field.
In case 3, the length Lc is not null; therefore the Lc field is present and the data field consists of the Lc subsequent bytes. The length Le is null; therefore the Le field is empty. Consequently, the body consists of the Lc field followed by the data field.
In case 4, the length Lc is not null; therefore the Lc field is present and the data field consists of the Lc subsequent bytes. The length Le is also not null; therefore the Le field is also present. Consequently, the body consists of the Lc field followed by the data field and the Le field.
So in my case it will be case 4 , I need to send some bytes, and get some bytes.
So the command in this case should be:
0x00 0x40 0x00 0x00 0x05 0x00 0x40 0x00 0x00 0x00 0x05;
CLA INS P1 P2 Lc b1 b2 b3 b4 b5 Le
Lc- input byte length (0x05 followed by 5 bytes of input: 0x00 0x40 0x00 0x00 0x00)
Le- expeted output byte length (H,e,l,l,o in my case it is 5 bytes. Hence 0x05)
and I got the repsonse as:
CLA:00 INS:40 P1:00 P2:00 Lc:05,00,40,00,00,00 Le:05,48,65,6c,6c,6f SW1:90 SW2:00
I got the Word H,e,l,l,o in the Le field.
As suggested by #Vojta ,And another mistake I did is, I am running the command without selecting the applet,
So, the correct order should be
power up
//create installer applet
//create testapplet
//select test appplet (I missed this step in my question)
//run get Hello Command
powerdown;