Save a data into smartcard

Question

Guys... I would like that you can help me in this case. I have the following requeriment to implement in a smartcard, I have to save a data(in a file) into the smartcard memory, e.g in the moment that the user inserts the card in the smartcard reader, the app must sent a appdu comand within a data(value = 1) inserted in it and this data(value) must be saved in the memory of the smartcard so that the method which writes the data is in the JavaCard Applet.. after running the first step the user extracts the card and then the user inserts the card in another smartcardreader and the applet reads this data from the memory
I don't know how does the applet "save or write" and "read" the data into the smartcard?
any suggestion?
best regards,
Marcos

Answer 1

You need
1) An Applet in the smart card to read, write and listen to commands (APDU)
2) You need a J2SE application on the PC attached with the reader to send and receive APDU.
Contents of 1)
A standard cardlet (Card Applet) with the process method that reads APDU's and writes them.
     // ----- program code for the APDU command PUT DATA
     public void cmdPUTDATA(APDU apdu) {
          byte[] cmd_apdu = apdu.getBuffer();
          // ----- check preconditions in the APDU header
          // check if P1=0
          if (cmd_apdu[ISO7816.OFFSET_P1] != 0) {
               ISOException.throwIt(ISO7816.SW_WRONG_P1P2);
          } // if
          // check if P2 contents an allowed tag value
          short tag = (short) (cmd_apdu[ISO7816.OFFSET_P2] & (short) 0x00FF);
          if ((tag < (short) 0x0040) || (tag > (short) 0x00FE)) {
               ISOException.throwIt(ISO7816.SW_WRONG_P1P2);
          } // if
          short lc = (short) (cmd_apdu[ISO7816.OFFSET_LC] & (short) 0x00FF); // calculate
                                                                                               // Lc
                                                                                               // (expected
                                                                                               // length)
          receiveAPDUBody(apdu); // get the command body
          // ----- check precoditions of security status
          if (pin.isValidated() == false) {
               ISOException.throwIt(ISO7816.SW_SECURITY_STATUS_NOT_SATISFIED);
          } // if
          // ----- command functionality
          short result = SetDO(lc, tag, apdu);
          // ----- prepare response APDU
          if (result == DO_PROPPER_SET) {
               ISOException.throwIt(ISO7816.SW_NO_ERROR); // command proper
                                                                      // executed
          } // if
          else if (result == NOT_ENOUGH_SPACE) {
               ISOException.throwIt(ISO7816.SW_FILE_FULL); // not enough free
                                                                      // memory
          } // else if
          else if (result == DO_HAVE_WRONG_LENGTH) {
               short index = GetIdxToDO((short) tag);
               short len = memory[(short) (index + LEN_TAG)]; // get the correct
                                                                           // length of the DO
               ISOException.throwIt((short) (ISO7816.SW_WRONG_LENGTH + len)); // send
                                                                                               // correct
                                                                                               // length
                                                                                               // back
          } // else if
          else { // this case should never happen, there must be an error in code
                    // above
               ISOException.throwIt(ISO7816.SW_UNKNOWN); // unknown error
          } // else
     } // cmdPUTDATA
     // ----- program code for the APDU command GET DATA
     public void cmdGETDATA(APDU apdu) {
          byte[] cmd_apdu = apdu.getBuffer();
          // ----- check preconditions in the APDU header
          // check if P1=0
          if (cmd_apdu[ISO7816.OFFSET_P1] != 0) {
               ISOException.throwIt(ISO7816.SW_WRONG_P1P2);
          } // if
          // check if P2 contents an allowed tag value
          short tag = (short) (cmd_apdu[ISO7816.OFFSET_P2] & (short) 0x00FF);
          if ((tag < 0x40) || (tag > 0xFE)) {
               ISOException.throwIt(ISO7816.SW_WRONG_P1P2);
          } // if
          short le = (short) (cmd_apdu[ISO7816.OFFSET_LC] & 0x00FF); // calculate
                                                                                     // Le
                                                                                     // (expected
                                                                                     // length)
          if (le > SIZE_MEMORY) {
               ISOException.throwIt(ISO7816.SW_WRONG_LENGTH);
          } // if
          // ----- command functionality
          short index = (short) GetIdxToDO(tag);
          if (index == DO_NOT_FOUND) { // DO not found
               ISOException.throwIt(SW_DATA_NOT_FOUND);
          } // if
          short len = (short) memory[(short) (index + LEN_TAG)]; // length of the
                                                                                // DO value
          len = (short) (len); // calculate length of the whole DO
          if (le != len) {
               ISOException.throwIt(ISO7816.SW_WRONG_LENGTH);
          } // if
          index = (short) (index + LEN_TAG + LEN_LEN); // index to the value of
                                                                      // the DO
          // ----- now all preparations are done, the data object can be send to
          // the IFD -----
          apdu.setOutgoing(); // set transmission to outgoing data
          apdu.setOutgoingLength((short) le); // set the number of bytes to send
                                                       // to the IFD
          apdu.sendBytesLong(memory, (short) index, (short) le); // send the
                                                                                // requested the
                                                                                // number of
                                                                                // bytes to the
                                                                                // IFD, data
                                                                                // field of the
                                                                                // DO
     } // cmdGETDATAContents of 2)
J2SE code to create the following and receive the response from the cardlet. To put and get data you can use these apdu's
// Specification of ISO/IEC 7816-4 case 3 command PUT DATA
//   command APDU               CLA = '00' || INS = 'DA' ||
//                              P1 (= '00') || P2 (= TAG ['40' ... 'FE']) ||
//                              Lc (= length of DATA) ||
//                              DATA (value field of the DO, with length Lc)
//   response APDU (all case)   SW1 || SW2
0x00 0xDA 0x00 0x40 0x10 0x31 0x32 0x33 0x31 0x32 0x33 0x34 0x33 0x33 0x31 0x32 0x32 0x32 0x33 0x33 0x32 0x00;
// Specification of ISO/IEC 7816-4 case 2 command GET DATA
//   command APDU               CLA = '00' || INS = 'CA' ||
//                              P1 (= '00') || P2 (= TAG ['40' ... 'FE'])
//                              Le (= length of expected data)
//   response APDU (good case)  DATA (value field of the DO, with length Le) ||
//                              SW1 || SW2
//   response APDU (bad case)   SW1 || SW2
0x00 0xCA 0x00 0x40 0x00 0x10;ofcourse you can use RMI too.
cheers
Enya