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Programming a Java Card

Applet. Install. Select. Process. Deselect. getShareableInterfaceObject. Programming a Java Card. The Applet Model Installation Create an applet instance Register the applet with the JCRE Selection Select the applet, do some initialization Processing

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Programming a Java Card

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  1. Applet Install Select Process Deselect getShareableInterfaceObject Programming a Java Card • The Applet Model • Installation • Create an applet instance • Register the applet with the JCRE • Selection • Select the applet, do some initialization • Processing • Process commands send from the host • Deselection • Clean up and state saving • get SIO • Deliver the reverence of the own instance

  2. Programming a Java Card (2) • Installation • Create an Applet instance • Call the Constructor • Create Applet objects • Register the Applet with the JCRE • Do Error Handling package com.gieseckedevrient.applets.myfirst; import javacard.framework.*; public class MyFirst extends Applet { // ---------------------------------------------- // Constructor // ---------------------------------------------- private MyFirst () { register (); } // -- END - static elements --------------------- // ---------------------------------------------- // Install method // ----------------------------------------------------------------- public static void install(byte[] buffer, short offset, byte length) { new MyFirst(); } // -- END - Public static void install( ... ) ----------------------

  3. Programming a Java Card (3) • Selection / Deselection • When an ISO 7816-4 select command is received • JCRE checks if the AID corresponds to an registered applet • If so, the active applet is first deselected and the applet with the correct AID is selected • Otherwise the command is transfered to the selected applet for processing • Command Processing • Get the APDU buffer • Decode the command header • Receive command data if needed • Perform command • Send response • Throw ISOException if status is not 90 00

  4. Programming a Java Card (8) - Processing (1) public void process(APDU o_apdu) throws ISOException { if( selectingApplet() ) { m_sz_Verified = false; return; } byte[] ba_buffer = o_apdu.getBuffer(); //Examination of the buffer. switch( ba_buffer[ ISO7816.OFFSET_INS ] ) { //PIN Verification as defined in ISO 7816-4. case VERIFY: // ---------------------------- s_databytes = receive( o_apdu ); s_dataoffset = Util.getShort( ba_buffer, ISO7816.OFFSET_P1 ); b_result = Util.arrayCompare( ba_buffer, (short) (ISO7816.OFFSET_CDATA & 0x00FF), m_sba_aPin, (short)0, s_databytes );

  5. Programming a Java Card (8) - Processing (2) if( b_result == (byte)0x00 ) { m_sz_Verified = true; } else ISOException.throwIt( ISO7816.SW_SECURITY_STATUS_NOT_SATISFIED ); break; case READ: // ----------------------------------------------------- if( !m_sz_Verified ) ISOException.throwIt(ISO7816.SW_SECURITY_STATUS_NOT_SATISFIED); o_apdu.setOutgoing(); o_apdu.setOutgoingLength( (short) 80 ); o_apdu.sendBytesLong( m_sba_userdata, (short)0, (short)80 ); break; default : // ------------------------------------------------------ ISOException.throwIt( ISO7816.SW_INS_NOT_SUPPORTED ); } } // -- END - public void process( ... ) throws ISOException -----------------

  6. Programming a Java Card (1) • The ISO-7816 APDU communication model Command APDU Response APDU Host Java Card

  7. Header (mandatory) Body (optional) CLA INS P1 P2 Lc DATA Le Programming a Java Card (2) • Command APDU • CLA - indicates the type of command (ISO, prop.) • INS - specifies the instruction to be performed • P1 and P2 - instruction parameters • Lc - number of bytes in the data field • Data - command optional data • Le - number of bytes expected in the response

  8. Body (optional) Trailer (mandatory) DATA SW1 SW2 Programming a Java Card (3) • Response APDU • Data - command optional response • SW1 and SW2 - status word

  9. RID register identifier PIX proprietary identifier extension 5 bytes Programming a Java Card (4) • Naming conventions in Java Card • All named resources use ISO 7816-5 AIDs • Named resources are • Packages (for loading, linking and deletion) • Applet Classes (for installation of applets) • Applet Instances (the real card applications) 0 to 11 bytes

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